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This work used a unified dynamic model of microbial fuel cells (MFCs) and microbial electrolysis cells (MECs) that were combined to create MFC-powered MECs. This allowed for a completely sustainable and green system of hydrogen production and wastewater treatment. The main advantage that was envisioned for this coupled system was the elimination of the need for an external power source; the only feed to the system was the wastewater itself. We present the results of parameter estimation and model validation. The results showed the importance of minimizing internal resistance to increase hydrogen production. Better powering of MECs was achieved by setting MFCs in series rather than in parallel.

The catalytic decomposition of methane (CDM) is a hydrogen and nanostructured carbon production process with minimal CO2 emission. Among the transition metal-based catalysts (e.g. Ni, Fe, Co, etc.), Ni-based catalysts are most widely studied due to the higher catalytic activity in decomposing methane. However, the limited lifespan of the catalyst makes it unsuitable for practical applications. Effective methane decomposition catalysts should be designed to optimize both reaction efficiency and catalyst lifetime. A Ni/CeO2 catalyst, developed in previous studies, Co was added to promote low-temperature (< 700 °C) activity manipulating the redox property of Co. Among the prepared catalysts with varying Ni:Co ratio, the methane conversion rate of the Ni8Co2/CeO2 catalyst was approximately twice that of the Ni10/CeO2 catalyst, confirming its excellent low-temperature activity. The reaction rate of Ni8Co2/CeO2 catalyst was 4.38 mmol/min∙gcat at 600 °C with WHSV of 36 L/gcat∙h. In terms of characteristics of carbon products, Raman spectroscopy analysis revealed that the carbon grown on the catalyst surface exhibited high crystallinity, with D-G band ratio (ID/IG) of 1.01. The fresh and used catalyst samples were characterized by TEM, XPS, XAS, and other methods to analyze the parameters affecting catalytic activity.

In this paper, to address gaps in the development of low-carbon energy systems, an innovative concept of an ammonia-methane Brayton cycle is proposed. This system is interconnected with various subsystems, including the Kalina cycle, high-temperature steam electrolysis, thermoelectric generators, and ammonia and methane synthesis reactors. The primary aim of this system was to reduce dependence on external resources by establishing local sources for water and fuel, thus reducing the environmental impact and enhancing energy sustainability. A thermodynamic model of an energy system was developed via EES codes which leads to a thoughtful perception into the interactions of the proposed system parameters. Also, comprehensive investigations involved the examination of different energy system scenarios. Modeling outputs of the proposed multigeneration system discovered excellent thermal efficiency and power production, with figures of 56.5 % and 17 MW, respectively, while the Brayton system showed the results of 23.7 % and 3.8 MW. This study also highlighted the environmental benefits of the multigeneration system by demonstrating a carbon dioxide emission of 0.058 kg/kWh, representing its significant positive impact on environmental sustainability. Also, the produced ammonia and methane within the system was 0.37 % and 9 %, of fuel in combustion chamber, respectively. Also, the rest of demand fuel was provided from the external resources.

Electrolysis from biomass is a promising process for hydrogen generation from biomass and biowaste that is still unexplored. The paper used lignocellulosic biomass components and food waste (banana and cucumber peels) as feedstocks to explore hydrogen generation through an H-type proton exchange membrane electrolytic cell. Polyoxometalates (PMo12) were employed as a catalyst and charge carrier during the pre-treatment stage in the biomass degradation process. Electrochemical characterisations were conducted in a potential range of 0–1.20 V to analyse the electrochemical reaction behaviour at the anode. To assess the impact of temperature on the hydrogen yield rates, the electrolysis was conducted at both room temperature (19 °C) and a higher temperature (80 °C). Results show that the maximum hydrogen produced in the first hour was 7.8 mL per gram of biomass. With an electrical potential of 1.20 V and a temperature of 80 °C, the hydrogen yield rate of glucose was three times higher than that of the individual biomass components, i.e., cellulose, lignin, hemicellulose, and starch. The volume of hydrogen yielded from banana peel and cucumber was 49.2 mL and 39.6 mL, respectively. The overall conversion efficiency was calculated as the weight percentage ratio of the hydrogen contained in cucumber and banana peels and the hydrogen collected was 10 % and 17 %, respectively, suggesting the need to identify solutions to extract the hydrogen content from biomass material further.

In solar energy utilization, photocatalytic hydrogen production has been widely researched. To address issues such as low efficiency of photocatalysts, Cu-doped Zn0.5Cd0.5S composite photocatalysts were prepared using a hydrothermal method for photocatalytic hydrogen production. The Cu/Zn0.5Cd0.5S photocatalyst was characterized using XRD, XPS, SEM, TEM, UV–vis-DRS, fluorescence spectrophotometer, and electrochemical workstation. The results indicate that Cu doping alters the crystal and band structures of Zn0.5Cd0.5S. Hydrogen production experiments were conducted under xenon lamp irradiation, and at 45 °C, the highest hydrogen production rate was 2.72 and 1.63 times that of single Zn0.5Cd0.5S and Cu-doped Zn0.5Cd0.5S at room temperature (25 °C), respectively. Cu doping imparted a photothermal effect to the photocatalytic hydrogen production experiment, enhancing its efficiency.Cu doping captured electrons by replacing some Zn, constructing an internal electric field, forming defect energy levels, which hindered electron-hole recombination. Additionally, Cu ions acted as a plasma, inducing a plasma effect during hydrogen production, accelerating the rate of solar energy conversion to thermal energy, thus improving hydrogen production efficiency. This research not only provides a photocatalyst for photocatalytic hydrogen production but also utilizes it for photothermal synergistic catalysis.

Urea oxidation reaction (UOR) and hydrogen evolution reaction (HER) are the key processes for implementing urinated water electrolysis and hydrogen green production, respectively. This contribution investigates the modification of commercial nickel foam (NF) with a nickel phosphate (NiPO/NF) heterostructure layer via anodizing in phosphate solution at various potentials (5, 10 and 15 V) as a simple and efficient route to boost the urea-assisted water electrolysis and hydrogen production in alkaline medium. The morphology and composition physicochemical characterisation of the phosphate layer exhibit aggregates of crystalline nanoparticles with interstitial mesoporous and macroporous networks with a mole composition ratio of 9.42: 1.0: 8.14 for Ni: P: O respectively. The electrochemical measurements revealed the NiPO/NF anodized at 10 V exhibits a superior electroactive surface area of 255 cm2, a substantially higher urea oxidation current compared to pristine NF, achieving 20 and 500 mA/cm2 at 1.35 and 1.6 V vs. RHE respectively and retained 100 % of activity during the urea electrolysis for more than 3 h. The electrochemical impedance analysis confirmed the alkaline urea oxidation reaction proceeded via indirect (EC) and direct mechanism and the CO2 intermediates adsorption–desorption became the predominant reaction at more positive potential. The NiPO/NF anode employed in an H-shape can deliver up to ±400 mA/cm2 for UOR/HER at a bias potential of 1.85 V and 8-fold (2.0 mmol/min) much higher hydrogen production rate compared to the pristine NF anode (0.25 mmol/min). Combining commercial nickel foam modification via anodizing and alkaline urea electrolysis at ambient conditions offers a unique and innovative solution for both large-scale hydrogen green production as well as remedy of the urinated wastewater for a more sustainable future.

The chemical looping gasification of plastics (CLGP) is a process that offers an innovative solution for transforming post-consumer waste plastics into high-value products. The process utilizes a co-current moving bed reducer reactor with iron-titanium-based oxygen carriers to gasify plastic feed and generate syngas autothermally. Its distinguishing feature is its ability to operate over a wide range of feed loadings and co-injection of mixed plastic species without any performance losses. Isothermal bench-scale experiments reveal a syngas purity of ∼95 %, aligning with the thermodynamic simulations. The moving bed reactor facilitates a deeper reduction of the oxygen carriers to the Fe+FeTiO3 phase, leading to the high syngas purity, which is then verified with additional TGA, XRD, and SEM analysis. For an autothermal operation of CLGP process, an active material content of 20 % is found to be sufficient to satisfy the kinetic and thermodynamic constraints. Further integration with downstream production of H2 is presented and compared to a steam gasification process. The process integration simulations show that the CLGP process outperforms the steam gasification system in terms of Cold Gas Efficiency (CGE), Effective Thermal Efficiency (ETE), and H2 yield. CO2 emissions are impressively reduced by ∼30 % in the CLGP system over that in the steam gasification system due to its ability to autothermally operate the process, unlike the highly endothermic steam gasification process.

Hydrogen energy systems (HES) are increasingly recognized as pivotal in cutting global carbon dioxide (CO2) emissions, especially in transportation, power generation, and industrial sectors. This paper offers a comprehensive review of HES, emphasizing their diverse applications and economic viability. By 2030, hydrogen energy is expected to revolutionize various sectors, significantly impacting CO2 abatement and energy demand. In electricity and power generation, hydrogen could reduce CO2 emissions by 50–100 million tons annually, requiring 10–20 million tons of hydrogen and an investment of $50–100 billion, underscoring its role in grid stabilization. Additionally, in the heating sector, hydrogen could facilitate a CO2 abatement of 30–50 million tons. We examine the levelized cost of hydrogen (LCOH) production, influenced by factors like production methods, efficiency, and infrastructure. While steam methane reforming is cost-effective, it poses a larger environmental impact compared to electrolysis. The global life-cycle cost of hydrogen production decreases as production scales up, with current costs ranging from $1–3 per kg for fossil-based sources to $3.4–7.5 per kg for electrolysis using low-emission electricity. These costs are projected to decrease, especially for electrolytic hydrogen in regions with abundant solar energy. However, despite the technical feasibility of decarbonization, high production costs still pose challenges. A systematic and effective transition to a hydrogen economy requires comprehensive policy and financial support mechanisms, including incentives, subsidies, tax measures, and funding for research and development of pilot projects. Additionally, the paper discusses hydrogen's role in advanced storage technologies such as hydrides and Japan's ENE-FARM solution for residential energy, emphasizing the need for strategic investments across the hydrogen value chain to enhance HES competitiveness, reduce LCOH, and advance the learning rates of hydrogen production technologies.

This research investigates the synthesis and application of Losod-zeolite (LOS-Z), a crystalline hydrated sodium aluminosilicate (Na12Al12Si12O48.xH2O) as a potential photocatalyst for dye degradation and H2 production from dye-degraded water. The photocatalytic properties are enhanced by impregnating molybdenum (Mo) into LOS-Z (Mo@LOS-Z). XRD, FTIR, SEM, EDX, and elemental mapping were used to study the physicochemical properties of synthesized materials while UV–vis and PL were employed to explore the optoelectronic properties. The photocatalytic activities for dye degradation and H2 production were evaluated using methylene blue (MB) under visible light irradiation. An enhancement in the efficiency of dye degradation (56%–82%) and H2 production rate was demonstrated due to the competitive photocatalytic performance of 10% Mo@LOS-Z compared to the pristine LOS-Z and CFA-BFA blend. It exhibited 2.5 times higher (∼1200 μmol g−1h−1) H2 production than the LOS-Z (∼480 μmol g−1h−1) due to the synergistic effects of narrowed band gap and recombination rate. This study could pave the way forward into the synthesis of waste-derived photocatalysts for efficient dye degradation and H2 production.

In order to achieve a sustainable, low-carbon energy future, it is necessary to develop innovative and integrated solutions. However, one of the main obstacles to the advancement of renewable energy is storage. With this in mind, hybrid systems combining solar energy and hydrogen production have great potential. This article focuses on the evaluation of a solar PV/T (photovoltaic-thermal) system coupled with an electrolyser for the joint production of hydrogen and heat. Simulations are performed in MATLAB. The analysis reveals that with PV/T power supply, the production potential is estimated at 179.6 W and 551.9 W respectively for electrical and thermal power. An in-depth study aimed at optimizing the system by evaluating the quality of the energy used in the water electrolysis process makes it possible to analyze the effect of certain operating parameters. With a water flow of 5.7 ×10−3 m3/h, a current density of 200 mA/ cm2 and an electrolyzer temperature of 60 °C, the monthly production of hydrogen and oxygen reaches the maximum values of 4.85 m3 and 2.42 m3 respectively. This led to a maximum exergy efficiency of 57.8 %. This study demonstrates the linearity between hydrogen production and current density which at high density reduces exergy performance.

To improve the performance of photovoltaic-electrolyzer (PV-EL) systems, it is key to operate them at the right operating conditions, not only at design point but also at off-design. In addition, when directly coupling a PV system to an EL one, an ideal sizing of the resulting PV-EL coupled system ensuring the best interaction between the PV system and the EL stack is not always possible. Coupling indirectly PV systems to EL ones, through DC/DC converters for instance, results thus advantageous. Accordingly, this work discusses the application of sliding mode control (SMC) to indirectly coupled PV-EL systems, which allows them to operate as efficient as possible. The control scheme employed here includes mathematical models for both the PV system and the EL stack, and for the DC/DC converter and the sliding mode control algorithm utilized. To determine their influence on the obtained results, two different converter topologies are assessed here. Some of the results obtained emphasize that using a DC/DC converter can significantly increase the hydrogen produced by PV-EL systems, especially when it is paired with a control algorithm like SMC. This effort represents one of the first works involving the application of sliding mode control to indirectly coupled PV-EL systems.

The transition from fossil fuels to carbon-neutral energy sources is necessary to reduce greenhouse gas (GHG) emissions and combat climate change. Hydrogen (H2) provides a promising path to harness fossil fuels to reduce emissions in sectors such as transportation. However, regional economic analyses of various H2 production techniques are still lacking. We selected a well-known fossil fuel-exporting region, the USA's Intermountain-West (I-WEST), to analyze the carbon intensity of H2 production and demonstrate regional tradeoffs. Currently, 78 % of global H2 production comes from natural gas and coal. Therefore, we considered steam methane reforming (SMR), surface coal gasification (SCG) and underground coal gasification (UCG) as H2 production methods in this work. We developed the cost estimation frameworks of SMR, SCG and UCG with and without carbon capture, utilization and sequestration (CCUS). In addition, we identified optimal sites for H2 hubs by considering the proximity to energy sources, energy markets, storage sites and CO2 sequestration sites. We included new production tax credits (PTCs) in the cost estimation to quantify the economic benefit of CCUS. Our results suggest that the UCG has the lowest levelized cost of H2 production due to the elimination of coal production cost. H2 production using the SMR process with 99 % carbon capture is profitable when the PTCs are considered. We also analyzed carbon utilization opportunities where CO2 conversion to formic acid is a promising profitable option. This work quantifies the potential of H2 production from fossil fuels in the I-WEST region, a key parameter for designing energy transition pathways.

The global increase in energy demand requires a continuous search for renewable and clean alternative resources to fossil fuels. Hydrogen is emerging as a promising energy carrier for the future; its production via photocatalysis, driven by sunlight, can directly convert solar energy into a usable or storable energy resource. However, water splitting requires sacrificial agents or electron donors/hole scavengers, such as short-chain organic acids. This research explores the use of lactic acid as a source for photocatalytic hydrogen production, offering valuable alternatives for wastewater management and renewable energy production. This study employed the innovative supercritical antisolvent (SAS) technique to micronize the precursors of both the active phase (CeO2) and co-catalyst (CuO), ensuring rapid and complete solvent removal and size reduction of photocatalyst precursors. The prepared samples were characterized by field emission scanning electron microscopy (FESEM), Fourier transform infrared (FT-IR) spectroscopy, dynamic light scattering (DLS) analysis, Brunauer-Emmett-Teller (BET) analysis and thermogravimetric analysis (TGA). This study has shown that the micronization process resulted in a notable improvement in CeO2 photocatalytic activity, attributed to the reduction of the dimensions of the powders. Hydrogen production was equal to 3989 μmol L−1 for the SAS-produced photocatalyst while using a commercial CeO2 sample resulted in H2 production of 2519 μmol L−1. The enhanced photoactivity of CeO2-CuO composites was found to be related to the presence of CuO. The optimal CuO amount was equal to 0.5 wt%, determining a hydrogen production of 9313 μmol L−1 after 4 h of UV irradiation time. A photocatalytic test carried out with deuterated water (D2O) instead of distilled H2O demonstrated that hydrogen was preferentially produced from water splitting reaction, whereas lactic acid acted as a sacrificial agent being oxidized from positive holes photogenerated in the valence band of CuO.

The unclear developmental potential of hydrogen production technologies in China hinders policy formulation and industrial planning. This study explores the evolution of nine hydrogen production pathways in China from 2020 to 2060, using a dynamic integrated assessment model. The results project a significant increase in hydrogen supply from 29.69 Mt in 2020 to 86.34 Mt by 2060, primarily green hydrogen post-2042, with an 83 % reduction in average carbon footprint during the forty years. The levelized cost when not considering carbon prices is projected to peak in 2033. The findings suggest a phased transition strategy, carbon pricing, and increased investments to promote a cost-effective, low-carbon hydrogen economy in China. This study provides a multi-dimensional perspective on China's long-term hydrogen industry development, offering insights for policymaking.

The pursuit of sustainable hydrogen production through the conversion of methane (CH4) and carbon dioxide (CO2), two prevalent greenhouse gases, is advanced by utilizing cost-effective Ni-supported catalysts within the framework of methane dry reforming. Utilizing crystalline porous zeolite, specifically ZSM-5, enhances the dispersion of nickel (Ni) across the catalyst surface and within its pore channels, hence increasing catalytic efficiency. Herein, we investigate the impact of incorporating various promoters (Ce, Cs, Cu, Fe, Sr) into the 5Ni/ZSM-5 catalyst, systematically examining how these modifications influence the reducibility, basicity, and crystallinity of the catalyst’s active sites, thereby affecting its hydrogen yield potential.Our findings reveal that the inferior activity of Cu-promoted catalysts is due to the depletion of basic sites and larger NiO crystallite size (than rest-promoted catalysts). The introduction of Fe results in a highly dispersed Ni with a stable NiFe phase, but dilution of active sites results in low hydrogen yield. Conversely, Sr promotion enhances the basicity and accessibility of NiO active sites both on the surface and within the pore channels of the zeolite, leading to a notable hydrogen yield of 28 % at 700℃ after 300 min. Furthermore, the addition of 2 wt% ceria significantly optimizes Ni dispersion within the pore channels and surges the maximum population of basic sites (including the presence of very strong basic sites), achieving 35 % hydrogen yield at 700 °C and ∼ 70 % at 800℃. This investigation underscores the critical role of promoter-induced modifications in enhancing catalyst performance for hydrogen production, contributing to the development of more efficient and sustainable energy conversion technologies.

This work focuses on the design of a reactor for producing clean hydrogen from methane pyrolysis in the form of the so-called “turquoise hydrogen”. In addition to its simple geometry, the fundamental concept and the main novelty of the proposed method rely on using part of the methane to produce the required heat needed for the thermal decomposition of methane (TDM). The reactor configuration for hydrogen production is shown to produce significant advantages in terms of greenhouse gas (GHG) emissions. A reactive flow CFD model incorporating also soot formation mechanism has been first developed and validated with experimental results available in the literature and then used to design and characterize the performances of proposed reactor configuration. 3D CFD simulations have been carried out to predict the behavior of the reactor configuration; a sensitivity analysis is used for clearing the aspect related to key environmental parameters, e.g., the global warming impact (GWI). The real potential of the proposed design resides in the low emissions and high efficiency with which hydrogen is produced at the various operating conditions (very flexible reactor), albeit subject to the presence of carbon by-product. This suggests that this type of methane conversion system could be a good substitute for the most common hydrogen production technologies.

The transition to cleaner energy sources, including renewables, introduces the need for versatile and transportable energy carriers such as hydrogen. This paper aims to quantify the hydrogen export competitiveness of all countries using a newly developed comprehensive index. The developed competitiveness index includes 21 indicators under four main categories: resource availability and potential, economic and financial potential, political and regulatory status, and industrial knowledge. Expert interviews and surveys are conducted to properly identify, choose and modify the categories and indicators, and to calculate the appropriate weight for each. Top-ranking countries include the United States, Australia, Canada, United Kingdom, China, Norway, India, Russia, Netherlands, and Germany, and they are poised to be significant players in the hydrogen market. Policy recommendations for growing the hydrogen production and export sector are given based on each category.

In the current study, a detailed assessment and multi-objective optimization of a geothermal-driven cogeneration system for producing hydrogen and electricity have been carried out. The system includes two parts; the primary cycle is the geothermal cycle, which extracts geothermal energy. The secondary cycle consists of an organic Rankine cycle (ORC) and a proton exchange membrane (PEM) electrolyzer. In order to enhance ORC performance, zeotropic mixes have been used as working fluids. The concentration on the destructive environmental impacts of the system, which has not been considered in prior studies, is the research’s main novelty. This study mainly focuses on environmental evaluation using Life Cycle Assessment (LCA) to decrease destructive environmental impacts. From the perspectives of energy, exergy, exergoeconomic, and exergoenvironmental (4E), the pentane (0.3)-butane (0.7) working fluid performed better than other working fluids. Energy and exergy efficiency for the cogeneration system increased by 19.34% and 58.67%, respectively. According to the results of the exergoenvironmental analysis, the PEM showed significant product environmental consequences at a speed of 261 mpts/h. The multi-objective optimization findings illustrated that energy efficiency and destruction cost in optimum conditions reach 20.06% and 22.64 $/h. Furthermore, exergy efficiency and destruction environmental impacts will reach 59.81% and 1762.11 mpts/h, respectively.

Bangladesh focuses on green energy sources to be a lesser dependent on imported fossil fuels and to reduce the GHG emission to decarbonize the energy sector. The integration of renewable energy technologies for green hydrogen production is promising for Bangladesh. Hybrid renewable plants at the coastline along the Bay of Bengal, Kuakata, Sandwip, St. Martin, Cox’sbazer, and Chattogram for green hydrogen production is very promising to solve the power demand scarcity of Bangladesh. Hydrogen gas turbine and hydrogen fuel cell configured power plant performances are studied to observe the feasibility/prospect to the green energy transition. The Plant’s performances investigated based on specification of the plant’s units and verified by MATLAB SIMULINK software. Fuels blending (different percent of hydrogen with fossil fuel/NG) technique makes the hydrogen more feasible as turbine fuel. The net efficiency of the fuel cell-based combined cycle configuration (74%) is higher than that of the hydrogen gas turbine-based configuration (51.9%). Moreover, analyses show that the increment of combined cycle gas turbine efficiency (+18.5%) is more than the combined cycle PEMFC configuration (+14%). Long-term storage of renewable energy in the salt cavern as green hydrogen can be a source of energy for emergency. A significant share of power can be generated by a numbers of green power plants at specified places in Bangladesh.

With the clear adverse impacts of fossil fuel-based energy systems on the climate and environment, ever-growing interest and rapid developments are taking place toward full or nearly full dependence on renewable energies in the next few decades. Estonia is a European country with large demands for electricity and thermal energy for district heating. Considering it as the case study, this work explores the feasibility and full potential of optimally sized photovoltaic (PV), wind, and PV/wind systems, equipped with electric and thermal storage, to fulfill those demands. Given the large excess energy from 100% renewable energy systems for an entire country, this excess is utilized to first meet the district heating demand, and then to produce hydrogen fuel. Using simplified models for PV and wind systems and considering polymer electrolyte membrane (PEM) electrolysis, a genetic optimizer is employed for scanning Estonia for optimal installation sites of the three systems that maximize the fulfillment of the demand and the supply–demand matching while minimizing the cost of energy. The results demonstrate the feasibility of all systems, fully covering the two demands while making a profit, compared to selling the excess produced electricity directly. However, the PV-driven system showed enormous required system capacity and amounts of excess energy with the limited solar resources in Estonia. The wind system showed relatively closer characteristics to the hybrid system but required a higher storage capacity by 75.77%. The hybrid PV/wind-driven system required a total capacity of 194 GW, most of which belong to the wind system. It was also superior concerning the amount (15.05 × 109 tons) and cost (1.42 USD/kg) of the produced green hydrogen. With such full mapping of the installation capacities and techno-economic parameters of the three systems across the country, this study can assist policymakers when planning different country-scale cogeneration systems.

This study explores the optimization of membrane reactor configurations to enhance hydrogen production through CH4 tri-reforming. The investigation employs ceramic membranes for oxygen, vapor, and carbon dioxide distribution within the reactor bed. A differential evolution algorithm is utilized alongside cuckoo search algorithm (CSA) and support vector regression (SVR) to determine optimal values for O2/CH4, H2O/CH4, and CO2/CH4 ratios, membrane thickness, and shell pressure, with hydrogen yield as the objective function. Results demonstrate that the oxygen membrane reactor achieves the highest hydrogen yield, reaching 2.02 and 1.75 for direct methanol synthesis and Fischer–Tropsch processes, respectively, representing a 7.98 % and 10.03 % increase compared to the conventional tri-reforming reactor. Furthermore, CSA and SVR emerge as invaluable tools, facilitating robust optimization and predictive modeling. The CSA efficiently navigates complex solution spaces to identify optimal parameters, while SVR accurately models relationships between input variables and hydrogen yield. Incorporating these methodologies enhances the effectiveness of membrane reactor design and synthesis gas production. This study contributes to advancements in clean energy technologies by providing insights into efficient hydrogen production methods using membrane reactors.

Operation strategy of the integrated wind-hydrogen system is the key to ameliorate the negative impacts of the fluctuated wind power on the hydrogen production capacity and durability of electrolyzer. However, the desalination system supplying pure water to electrolyzers was neglected previously, with which the practical operation strategy of the hybrid wind-hydrogen-desalination system has yet to be investigated. In this work, we proposed a novel control strategy named step-by-step start for wind-hydrogen-desalination system consisting of wind turbine, proton exchange membrane water electrolyzer (PEMWE), battery and batch reverse osmosis (BRO) desalination system, which can produce hydrogen and fresh water. Real-time wind data from Shenzhen, China were used as input to the integrated system. The results demonstrate the wind-hydrogen-desalination system with the proposed strategy can improve the hydrogen production by 17.55 %, the energy efficiency by 17.68 % in August, and increase hydrogen production by 10.29 %, the energy utilization efficiency by 10.44 % in December compared with traditional strategies. At low wind speeds, the switching times of PEMWE for this strategy is higher than the other strategies, while at high wind speeds, the switching times of PEMWE is significantly decreased. This work provides insights into the practical operation strategy for wind-hydrogen-desalination system depending on the real-time wind speed.

With the cost of green hydrogen production decreasing year by year, methanation, a carbon dioxide hydrogenation reaction, is becoming a more critical technology for the realization of a carbon-neutral society. Here, we show the procedure of membrane preparation for a distributor-type membrane reactor that simultaneously captures and recycles CO2 together with experimental tests of the proposed reactor design. To decrease the temperature gradient in the reactor and to improve methane recovery from the inlet gas mixture, a three-dimensional computational fluid dynamics simulation of the reactor was conducted. The numerical results suggest that the distributed feed design results in a uniform distribution of carbon dioxide, preventing localized reactions at the reactor inlet. In addition, it reduces the temperature rise in the reactor by up to about 300 K compared to the case where the carbon dioxide and hydrogen gas mixture is fed from a single inlet. The effect of the feed CO2 concentration on reactivity is also discussed. Simulation results show that the membrane reactor with inlet concentration of about 15 %, such as those emitted from industrial boilers, is capable of recovering methane at concentrations about 1.5 times higher in comparison to 100 % CO2 concentration at the inlet in a classical reactor.

Modern energy conversion technologies with low or no emissions are needed to achieve sustainable development goals. This research examines the thermodynamic and exergy-economic features of a high-temperature proton exchange membrane fuel cell. A cutting-edge, integrated energy system uses high-temperature proton exchange membrane fuel cells, an organic Rankine cycle, a proton exchange membrane electrolyzer, and a multi-effect desalination unit. This setup generates electricity, hydrogen, and fresh water. Methanol-steam reformation produces hydrogen for the fuel cell. The recommended cycle drives an organic Rankine power producing cycle using 120–200 °C waste heat from high-temperature proton exchange membrane fuel cell to power water electrolysis and hydrogen generation. An integrated method incorporates energy and exergy balances and cost analysis to assess the proposed system's exergetic, economic, and environmental impacts. The suggested integration delivers high energy and exergy efficiency at an acceptable cost and environmental effect. According to parametric research, boosting the fuel cell's working temperature decreases production costs and carbon dioxide emissions per mass. Raising current density has positive technical and environmental impacts. As the current density increases from 0.4 to 0.8 (A/cm2), the net power generation increases to 46.67% and the exergy efficiency increases from 64.5% to 68%. An increase in multi-effect distillation motivate steam pressure from 200 to 600 kPa results in an increase in the daily freshwater generated from 111.68 m3 to 116.41 m3. For environmental protection and output optimization, fuel utilization ratio must be reduced. The ideal system's exergy efficiency, product unit cost, and environmental impact are 65.78%, 86.28 ($/h), and 4.33%, respectively.

One of the most important solutions to overcome energy and environmental problems and to replace the fossil fuel-based economy could be the use of photosynthetic microorganisms. The use of photosynthetic microorganisms is a potential alternative to energy generation from fossil fuels because they efficiently produce hydrogen (H2). Immobilization of photosynthetic microorganisms is used for many biotechnological applications such as H2 production. This method appears attractive because it restricts cell movement in an entrapped matrix. Immobilization of Rhodopseudomonas sp. S16-VOGS3 cells is a promising way to improve H2 production. In this work, the ability of immobilized Rhodopseudomonas sp. S16-VOGS3 cells to produce H2 was investigated in two types of PBRs. The PBRs used in this work were a cylindrical one with 0.2 ​L working volume (C-PBR) and a flat Roux type with 0.6 ​L working volume (FRT-PBR). The calcium alginate beads prepared were resistant to culture mixing and showed little leakage of cells, and the immobilized cells continued the photofermentation process in both PBRs. The immobilized cells in the C-PBR produced 936.8 ​mL of H2 with an average H2 production rate of 2.99 ​mL/h. The average productivity was 126.4 ​μL (H2)/mg (cells)/h or 14.96 ​mL (H2)/L (culture)/h, and the light conversion efficiency was 2.37 ​%. The immobilized cells in the FRT-PBR produced a total of 662.2 ​mL of H2 with an average H2 production rate of 1.55 ​mL/h. The average productivity was 31.1 ​μL (H2)/mg (cells)/h or 2.58 ​mL (H2)/L (culture)/h, and the light conversion efficiency was 0.52 ​%. The more uniform and therefore more efficient degree of bacterial cell mixing achieved in the C-PBR with cylindrical configuration played an important role compared to the FRT-PBR. In the FRT-PBR, the beads were aggregated at the bottom, which limited light penetration and resulted in low H2 production efficiency.

Transition to carbon neutrality requires the development of more sustainable pathways to synthesize the next generation of chemical building blocks. Electrochemistry is a promising pathway to achieve this goal, as it allows for the use of renewable energy to drive chemical transformations. While the electroreduction of carbon dioxide (CO2) and hydrogen evolution are attracting significant research interest, fundamental challenges exist in moving the research focus toward performing these reactions on scales relevant to industrial applications. To bridge this gap, we aim to facilitate researchers' access to flow reactors, which allow the characterization of electrochemical transformations under conditions closer to those deployed in the industry. Here, we provide a 3D-printable flow cell design (manufacturing cost < $5), which consists of several plates, offering a customizable alternative to commercially available flow reactors (cost > $6,000). The proposed design and detailed build instructions allow the performance of a wide variety of chemical reactions in flow, including gas and liquid phase electroreduction, electro(less)plating, and photoelectrochemical reactions, providing researchers with more flexibility and control over their experiments. By offering an accessible, low-cost reactor alternative, we reduce the barriers to performing research on sustainable electrochemistry, supporting the global efforts necessary to realize the paradigm shift in chemical manufacturing.

This review presents a broad exploration of the techno economic evaluation of different technologies utilized in the production of hydrogen from both renewable and non-renewable sources. These encompass methods ranging from extracting hydrogen from fossil fuels or biomass to employing microbial processes, electrolysis of water, and various thermochemical cycles. A rigorous techno-economic evaluation of hydrogen production technologies can provide a critical cost comparison for future resource allocation, priorities, and trajectory. This evaluation will have a great impact on future hydrogen production projects and the development of new approaches to reduce overall production costs and make it a cheaper fuel. Different methods of hydrogen production exhibit varying efficiencies and costs: fast pyrolysis can yield up to 45% hydrogen at a cost range of $1.25 to $2.20 per kilogram, while gasification, operating at temperatures exceeding 750 °C, faces challenges such as limited small-scale coal production and issues with tar formation in biomass. Steam methane reforming, which constitutes 48% of hydrogen output, experiences cost fluctuations depending on scale, whereas auto-thermal reforming offers higher efficiency albeit at increased costs. Chemical looping shows promise in emissions reduction but encounters economic hurdles, and sorption-enhanced reforming achieves over 90% hydrogen but requires CO2 storage. Renewable liquid reforming proves effective and economically viable. Additionally, electrolysis methods like PEM aim for costs below $2.30 per kilogram, while dark fermentation, though cost-effective, grapples with efficiency challenges. Overcoming technical, economic barriers, and managing electricity costs remains crucial for optimizing hydrogen production in a low-carbon future, necessitating ongoing research and development efforts.

This study aims to find an eco-friendly dual material to apply toward energy and antibacterial industry, and to identify their active sites. Cu0.1Zn0.9O nanoparticles (NPs) containing 10 % Cu ions into ZnO framework are synthesized using a facile hydrothermal method, and 10, 20, 30, or 40 nm-sized Ag NPs are loaded to obtain Ag@Cu0.1Zn0.9O particles. From the time-dependent increase in photocurrent density, it is confirmed that the Ag NPs has a photoelectron harvesting ability. Unlike ZnO and Cu0.1Zn0.9O, the Ag@Cu0.1Zn0.9O catalyst well splits water to generate hydrogen. Particularly, the catalyst loaded with 30 nm Ag NPs achieves the highest hydrogen production efficiency of 424.54 μmolg−1. This proves that the active sites generating hydrogen during water splitting are the Ag NP surfaces grafted onto the conduction band of the Cu0.1Zn0.9O particles. Contrastingly, antibacterial performances against Bacillus manliponensis are expressed in all samples of ZnO, Cu0.1Zn0.9O, and Ag@Cu0.1Zn0.9O. The antibacterial performance for the Ag NP-loaded sample slightly increases but it is not significant, indicating that the active site exhibiting the antibacterial activity is the hole+ of the valence band of Cu0.1Zn0.9O. In the end, this study revealed that the advantageous photocatalytic activity does not always express effective antibacterial activity because the active sites exhibiting photocatalytic and antibacterial properties may not be the same.

With a limited global carbon budget, it is imperative that decarbonisation decisions are based on accurate, holistic accounts of all greenhouse gas (GHG) emissions produced to assess their validity. Here the upstream GHG emissions of potential UK offshore Green and Blue hydrogen production are compared to GHG emissions from hydrogen produced through electrolysis using UK national grid electricity and the ‘business-as-usual’ case of continuing to combust methane. Based on an operational life of 25 years and producing 0.5MtH2 per year for each hydrogen process, the results show that Blue hydrogen will emit between 200-262MtCO2e of GHG emissions depending on the carbon capture rates achieved (39%–90%), Green hydrogen produced, via electrolysis using 100% renewable electricity from offshore wind will emit 20MtCO2e, and hydrogen produced via electrolysis powered by the National Grid will emit between 103-168MtCO2e, depending of the success of its NetZero strategy. The ‘business-as-usual’ case of continuing to combust methane releases 250MtCO2e over the same lifetime. This study finds that Blue hydrogen at scale is not compatible with the Paris Agreement, reduces energy security and will require a substantial GHG emissions investment which excludes it from being a ‘low carbon technology’ and should not be considered for any decarbonisation strategies going forward.

This paper describes a renewable energy system incorporating a hydrogen production unit to address the imbalance between energy supply and demand. The system utilizes renewable energy and hydrogen production energy to release energy to fill the power gap during peak demand power supply for demand peaking and valley filling. The system is optimized by analyzing marine predator behavioral logic and optimizing the system for maximum operational efficiency and best economic value. The results of the study show that after the optimized scheduling of the hydrogen production coupled renewable energy integrated energy system using the improved marine predator optimization algorithm, the energy distribution of the whole energy system is good, with the primary energy saving rate maintained at 24.75%, the CO2 emission reduction rate maintained at 42.32%, and the cost saving rate maintained at 0.78%. In addition, this paper uses the Adaboost-BP prediction model to predictively analyze the system. The results show that as the price of natural gas increases, the advantages of the combined hydrogen production renewable integrated energy system proposed in this paper become more obvious, and the cumulative cost over three years is better than other related systems. These research results provide an important reference for the application and development of the system.

Fusel oil is mixed alcohol as a by-product of ethanol production, and it can be used as a cheap and renewable source to produce Hydrogen (H2) via steam reforming. Silicon carbide (SiC) was successfully synthesized by pyrolysis of rice husk at different temperatures (1300, 1500, and 1700 °C) and was used as a support for a nickel (Ni) catalyst in steam reforming of fusel oil. The results exhibited pyrolysis temperature had a significant effect on the structure and crystalline phase of SiC, where pyrolysis of rice husk over 1500 °C resulted in the formation of a rod structure and β-SiC phase. The surface area of pyrolyzed rice husk was obtained for 19, 64, and 25 m2/g at pyrolysis temperatures of 1300, 1500, and 1700 °C, respectively. The performance of the Ni on the pyrolyzed rice husk support on steam reforming of fusel oil (SRF) was investigated at 700 °C and compared with Ni on commercial SiC. The Ni/SiC1500 exhibited the highest catalytic performance, and its activity remained almost constant during a 300 min stability test. The H2yield produced from the Ni/SiC1500 was 29% after 180 min and remained stable because the unique rod structure and β-SiC phase reduced carbon formation, thus giving an excellent performance.

The production of green hydrogen by water splitting from renewable energy is of great significance for achieving sustainable energy development. Alkaline water electrolysis (AWE) is the most economical and feasible route at present due to its earth-abundant catalysts, but it is desirable and crucial to improve the efficiency and purity of hydrogen production. Hydrogen production purity and energy consumption affect the fluctuation range of input power and economy respectively. In this paper, an electrolyzer with independent fluid flow path (IFP) is designed, which improves the problem of shutting current, hydrogen purity and hydrogen production efficiency. It has the characteristics of bipolar plate, zero gap and IFP. A test platform was built to verify its performance. The results showed that the IFP structure significantly improved the purity of hydrogen production, and the energy efficiency value increased by more than 3.29%.

This study conducts a thorough analysis of an integrated system that has been specifically engineered to generate power and hydrogen concurrently by utilizing biomass and an Organic Rankine Cycle (ORC). Under its feed fluid heater and heat recovery exchanger, the ORC exhibits a dual-generation capability and is powered by biomass combustion. This research investigates a range of ORC configurations that utilize unique working fluids specifically designed for hydrogen production. A comprehensive thermodynamic model is applied to each fluid. An essential goal is to perform a parametric analysis, wherein the impact of critical parameters on the overall performance of the system is thoroughly examined. In addition, an innovative system comprising an integrated proton membrane exchange electrolyzer and biomass in ORC is presented in this study. An evaluation of the energy and exergy efficiencies of five distinct working fluids (R113, R114, R218, RC318, and R236fa) is conducted. The R113 working fluid exhibited the highest energy and exergy efficiencies, whereas the other fan working fluids were found to possess noteworthy characteristics. The R113 working fluid exhibits exergy and energy efficiencies of 67.15 % and 3.69 %, respectively. In addition, the study reveals valuable information regarding exergy losses in the electrolyzer and evaporator, emphasizing their impact on the generation of electricity. This study clarifies the correlation between fluctuations in temperature within the biomass fluid and the subsequent alterations in power and hydrogen generation, uncovering a compromise characterized by a reduction in energy and exergy efficiency. Furthermore, the research illustrates how escalating the mass flow rates of biomass fluids results in a decline in energy and exergy efficiency while concurrently generating power and hydrogen.

Titanium dioxide (TiO2) composites are popular photocatalysts for hydrogen production from water. Here we report a composite consisting of S and N co-doped graphene quantum dots (SN-GQDs) with (001)TiO2 for photocatalytic hydrogen production. In addition to traditional advantages like light absorption promotion and charge transfer improvement, the as-prepared SN-GQDs/(001)TiO2 composite could significantly enhance the surface reaction by promotion of the formation of hydroxyl radicals, which results in the increase of the hydrogen production activity by 40 times. This work reveals the importance of surface reaction promotion by GQDs for hydrogen production, which will help researchers understand relevant systems comprehensively.

The urgent need for sustainable energy solutions and greenhouse gas mitigation has driven extensive research into advanced materials and technologies. This review provides an overview of the recent developments and advancements in the synthesis and application of carbon nanotubes for the integrated hydrogen production process with carbon dioxide capture and conversion. This work highlights the key methods employed for the synthesis of carbon nanotubes, including chemical vapor deposition, arc discharge, and laser ablation methods. The structural and morphological characteristics of these nanocomposites are explored, emphasizing their influence on catalytic activity, selectivity, and stability in hydrogen production reactions. Furthermore, the role of carbon nanotubes in carbon dioxide capture and conversion is discussed. These materials serve as efficient sorbents for CO2 capture due to their high surface area and tunable surface chemistry. Moreover, carbon nanotube-based catalysts integrated into nanocomposites facilitate the conversion of captured CO2 into value-added products, such as hydrocarbons of different functionalities. The challenges and opportunities associated with hydrogen production and CO2 capture and conversion are thoroughly addressed using carbon nanotubes. In summary, these multifunctional materials hold great promise in contributing to a sustainable and clean energy future while mitigating the effects of climate change.

Developing an efficient photocathode system from earth abundant materials is essential for effectual Photoelectrochemical (PEC) water splitting. Charge transfer between heterojunctions is important in fabricating a novel photocathode, keeping cost-effectiveness, abundance, and PEC performance in mind. The p-type narrow band gap photocathode, CuO (Eg = 1.5 eV) synthesized by hydrothermal method, was decorated with Sb2S3 Nanospheres (NSs) by adopting a facile chemical bath deposition (CBD) procedure to fabricate CuO/Sb2S3 NSs heterojunction. Fabricated heterojunction showed better PEC performance contrary to bare CuO, improvement in photocurrent density CuO/Sb2S3 NSs (J = −1 mA cm−2) than CuO (J = −0.3 mA cm−2) photoelectrode at 0 VRHE in 0.5 M Na2SO4 (pH 6.85) is due to enhanced charge carrier generation/separation. The photostability of CuO/Sb2S3 remains intact for 2.5 h with no degradation in photocurrent density. Sb2S3 works as a sensitizer, diminishing the recombination rate of the e−/h+ in CuO/Sb2S3 NSs. UV–Visible and photoluminescence(PL) emission spectra results suggested CuO/Sb2S3 enhanced absorption spectrum and reduced rate of recombination. Electrochemical impedance spectroscopy studies show less charge transfer resistance for CuO/Sb2S3 NSs than CuO. This finding will pave new path in developing novel photocathodic material configurations and heterojunction with Cu-based binary oxides/chalcogenides for solar harvesting.

Currently, meeting the global energy demand is largely dependent on fossil fuels such as natural gas, coal and oil. Fossil fuels represent a danger to the Earth's environment and its biological systems. The utilisation of these fuels results in a rise in atmospheric CO2 levels, which in turn triggers global warming and adverse changes in the climate. Furthermore, these represent finite energy resources that will eventually deplete. There is a pressing need to identify and harness renewable energy sources as a replacement for fossil fuels in the near future. This shift is expected to have a minimal environmental impact and would contribute to ensuring energy security. Hydrogen is considered a highly desirable fuel option with the potential to substitute depleting hydrocarbon resources. This concise review explores diverse methods of renewable hydrogen production, with a primary focus on solar, wind, geothermal, and mainly water-splitting techniques such as electrolysis, thermolysis, photolysis, and biomass-related processes. It addresses their limitations and key challenges hampering the global hydrogen economy's growth, including clean value chain creation, storage, transportation, production costs, standards, and investment risks. The study concludes with research recommendations to enhance production efficiencies and policy suggestions for governments to mitigate investment risks while scaling up the hydrogen economy.

Hydrogen as an energy source has been identified as an optimal pathway for mitigating climate change by combining renewable electricity with water electrolysis systems. Proton exchange membrane (PEM) technology has received a substantial amount of attention because of its ability to efficiently produce high-purity hydrogen while minimising challenges associated with handling and maintenance. Another hydrogen generation technology, alkaline water electrolysis (AWE), has been widely used in commercial hydrogen production applications. Anion exchange membrane (AEM) technology can produce hydrogen at relatively low costs because the noble metal catalysts used in PEM and AWE systems are replaced with conventional low-cost electrocatalysts. Solid oxide electrolyzer cell (SOEC) technology is another electrolysis technology for producing hydrogen at relatively high conversion efficiencies, low cost, and with low associated emissions. However, the operating temperatures of SOECs are high which necessitates long startup times. This review addresses the current state of technologies capable of using impure water in water electrolysis systems. Commercially available water electrolysis systems were extensively discussed and compared. The technical barriers of hydrogen production by PEM and AEM were also investigated. Furthermore, commercial PEM stack electrolyzer performance was evaluated using artificial river water (soft water). An integrated system approach was recommended for meeting the power and pure water demands using reversible seawater by combining renewable electricity, water electrolysis, and fuel cells. AEM performance was considered to be low, requiring further developments to enhance the membrane's lifetime.

In-situ hydrogen production and CO2 conversion to fuels have attracted significant attention as rational solutions to alleviate energy crises and climate issues. However, the implementation of such technology in large-scale industrial applications is still hampered by its inefficiency, considering the large energy barrier. Therefore, the fabrication of extremely efficient catalysts has become the main challenge in this field. Carbon nanotubes (CNTs) have recently been recognized as an encouraging electrocatalyst for such a process. CNTs-based electrocatalysts revealed remarkable catalytic activity in water-splitting reactions, proving that these materials are promising candidates for electrochemical processes. Carbon nanotubes with electron acceptor attributes facilitate charge separation, resulting in improved catalytic activity. This is primarily due to its exceptional physicochemical properties, i.e., enormous surface area, superior electrical conductivity, good thermal properties, and high melting point. This review highlights recent advances in the application of CNTs and CNTs-based catalysts in hydrogen production and CO2 conversion, focusing on detailed discussions on their preparation, modification, characterization, and catalytic performances. In addition, several possible challenges for further improvement of the CNTs catalytic system are also highlighted.

Hydrogen production via electrochemical water splitting demands high working voltages (>1.23 ​V) and hence incurs high electricity costs, encumbering its large-scale applications. The development of more high-efficiency and electricity-saving systems for hydrogen production is of great significance. Hydrazine oxidation reaction (HzOR)-assisted hydrogen production technology, which is constructed by replacing the anodic oxygen evolution reaction in pure water electrolysis systems with the HzOR, can greatly reduce the working voltage and electricity consumption, and hence shows great application prospects. In recent years, numerous studies have focused on designing various bifunctional electrocatalysts to simultaneously catalyze the cathodic and anodic reactions in HzOR-assisted hydrogen production systems. However, comprehensive reviews summarizing and commenting on this field are scarce. This review provides a systematic and insightful overview of the developments in HzOR-assisted hydrogen production technology from 2017 to the present, primarily focusing on catalyst design strategies, catalytic mechanisms, and economic and application analysis. Additionally, this review discusses several challenges and outlines future research directions in this field to attract more researchers' attention and accelerate the research and potential applications of HzOR-assisted hydrogen production technology.

This study presents a comprehensive investigation of a thermally integrated membrane micro reactor for efficient hydrogen production through the conversion of methane with water vapor. The reactor design incorporates a catalytic Au/ZnO system to enhance performance. The effects of key operational variables, including inlet gas flow rate, pressure, temperature, water-to-methane ratio, and membrane thickness, were examined. Optimal conditions were sought to maximize methane conversion, hydrogen yield, and minimize carbon monoxide production. As feed flow increases, methane conversion decreases due to reduced retention time in the reactor. This decrease is almost six times greater at 240 °C than at 270 °C. Higher water-to-methane ratios improved methane conversion and reduced hydrogen and carbon monoxide production. Shell pressure affected methane conversion, with higher pressures resulting in decreased rates and carbon monoxide levels. As shell airflow velocity increases, methane conversion rises about 0.96 %. Tube pressure influenced hydrogen passage through the membrane, causing decreased hydrogen output from the tube section and increased output from the shell section, while reducing carbon monoxide emissions. These findings contribute to the optimization of a thermally integrated membrane micro reactor for efficient hydrogen production through water vapor-methane conversion.

Recently the urea and urinated wastewater electrolysis process has shown promising technology for hydrogen fuel green production in addition to denitrification of wastewater. However, to make the process economically valuable, the electrocatalysts nanoarchitecture, nanometer size, shape, facets, and composition need to be engineered to boost the urea oxidation reaction (UOR). This work demonstrates a simple and novel approach to the synthesis of mesoporous nickel phosphate nanoparticles (meso-NiPO) via chemical deposition from a surfactant liquid crystal template. Typically, the nickel ions dissolved in the aqueous domain of the hexagonal liquid crystalline phase of the Brij®78 template were chemically reacted with the sodium phosphate solution to precipitate the mesoporous nickel phosphate nanoarchitecture after washing up the surfactant. The physicochemical characterizations show the meso-NiPO exhibits an amorphous highly mesoporous structure with a higher specific surface area (43.50 m2/g) compared to the bare nickel phosphate (bare-NiPO, 4.26 m2/g) prepared in the absence of surfactant. The electrochemical performance of meso-NiPO electrocatalyst for the urea oxidation reaction in alkaline solution exhibits superior activity including a lower oxidation onset potential (0.30 V vs. Ag/AgCl), charge transfer resistance (3.35 O) and mass activity of 700.7 mA/cm2 mg at the oxidation potential of 0.6 V vs. Ag/AgCl. Moreover, the meso-NiPO reveals long-term stability, and 97.5% of the steady-state oxidation current was maintained after the 3-hour urea electrolysis test. Using an H-shape urea electrolyzer, the corresponding cathodic hydrogen production rate reached 415 µmol/h and a Faradic efficiency of 96.8 % at an applied bias of 2.0 V. The electroactivity high performance of the mesoporous nickel phosphate is ascribed to the high specific surface area and mesoporous architecture that provide efficient charge transfer, as well as mass transport of the electroactive species. The chemical deposition from a surfactant liquid crystal template has the advantages of a one-pot template, applicable to the synthesis of a wide range of nanomaterials with various compositions and nanoarchitectures at room temperature for application in electrochemical energy production and storage systems.

Hydrogen (H2) fuel has the potential to replace fossil fuel for generating electricity, clean energy and generating power. Ammonia (NH3) has the potential to overcome the challenges associated with storage, transportation, and use of hydrogen fuel. The catalytic decomposition of ammonia into hydrogen is studied over cobalt catalysts supported on CaO-CeO2 mixed oxide. The influence of the Ca/Ce ratio in the support composition on catalytic activity was investigated. The CaO-CeO2 mixed oxide support materials prepared with different Ca/Ce ratios (1:1, 2:1 and 3:1). The overall basicity of catalyst varied with the increase of Ca to CaO-CeO2 mixed oxide and showed maximum at Ca/Ce = 2. The cobalt catalysts are prepared with a nominal 5 wt% Co over CaO-CeO2 mixed oxide support with various Ca/Ce ratios. Among all prepared catalysts 5CoCaCe-21 (5 wt%Co on CaO-CeO2 mixed oxide with Ca/Ce = 2) showed highest activity. Surface area, X-ray diffraction (XRD), Temperature Program Reduction (TPR), Scanning Electron Microscopy (SEM), and CO2 Temperature Program Desorption (TPD) methods were used to characterize the synthesized materials. The high performance of 5CoCaCe-21 catalyst is due to high basicity, suitable metal support interactions, high surface area and easy reducibility of Co species resulting from its support favorable properties. The effect of cobalt loadings also studied on CaCe-21 support. The 10 wt%Co on CaCe-21 (10CoCaCe-21) showed highest activity among all other cobalt loadings. The 10CoCaCe-21 catalyst showed excellent stability for H2 production from NH3 during 70 h of time on study with different GHSVs.

Hydrogen (H2) production using a biological pathway such as anaerobic digestion suffers limitations in the survival of microorganisms. Usually, microalgae are used as feedstock but the acidic pH of digestate ruptures the cell wall of microalgae resulting in dead cellular debris. Whereas some cyanobacteria (blue-green microalgae) are very resilient and tolerant to stressful environments such as hypersaline conditions. Therefore, in this study, a microbial consortium (co-culture) of cyanobacteria Phormidium keutzingianum and activated sludge bacteria (ASB) was established to generate H2 production from waste resources. Different co-culturing ratios 2:1, 1:1, and 1:2 v/v (P. keutzingianum: ASB) were analyzed for H2 production with glucose, sorbitol, and mannitol as carbon substrates. In addition, the effect of different concentrations (0, 10, and 20 g/L) of salt (NaCl) on H2 production was also tested. Results indicated that the amount of cumulative H2 produced changed significantly by varying the carbon substrates. Glucose-supplemented co-culture produced the lowest amount of H2 at 278 mL/L as compared to 980 and 562 mL H2/L in sorbitol and mannitol-supplemented co-cultures, respectively. The addition of NaCl negatively affected H2 production by increasing the salinity level from 0 to 20 g/L, and the cumulative H2 reduced from 980 to 176.8 mL/L and 562 to 333 mL/L in sorbitol and mannitol-supplemented co-culture, respectively. Sorbitol showed cyanobacterial growth in terms of chlorophyll from 600 to 1200 μg/L and optical density from 1 to 12 at λ 620 nm. Total organic carbon (TOC) in sorbitol supplemented co-cultures also increased to the peak 5.7, 6.7, and 7.7 g/L in 2:1, 1:2, and 1:1 v/v ratios, respectively, indicating anaerobic growth. Hence, this study signifies that sorbitol appeared to be the significant carbon substrate that helped cyanobacteria grow under anaerobic conditions resulting in higher H2 production. Moreover, cyanobacteria are more tolerant to stressful environments such as hypersaline and acidic conditions compared to microalgae.

This paper progressed in relation to literature by comparing three methods of Ni/Al2O3 deposition on cordierite monoliths, characterized and evaluated in methane steam reforming. The citrate method presented strong adherence of a uniform catalyst layer but exhibited only 7% of methane conversion at 800 °C and H2O/CH4 = 3. In contrast, Ni/Al2O3 co-precipitated deposition exhibited 99% of methane conversion but the lowest adherence. At least, Al2O3 coating followed by NiO wet impregnation showed strong adherence of the catalyst layer and high activity (98% conversion), attributed to nickel availability on the cordierite surface, proving to be the most efficient and suitable deposition method.

Hydrogen energy, the cleanest fuel, presents extensive applications in renewable energy technologies such as fuel cells. However, the transition process from carbon-based (fossil fuel) energy to desired hydrogen energy is usually hindered by inevitable scientific, technological, and economic obstacles, which mainly involves complex hydrocarbon reforming reactions. Hence, this paper provides a systematic and comprehensive analysis focusing on the hydrocarbon reforming mechanism. Accordingly, recent related studies are summarized to clarify the intrinsic difference among the reforming mechanism. Aiming to objectively assess the activated catalyst and deactivation mechanism, the rate-determining steps of reforming process have been emphasized, summarized, and analyzed. Specifically, the effect of metals and supports on individual reaction processes is discussed followed by the metal-support interaction. Current tendency and research map could be established to promote the technology development and expansion of hydrocarbon reforming field. This review could be considered as the guideline for academics and industry designing appropriate catalysts.

The affordability and availability of water and energy have a huge impact on food production. Research has shown that there exists a direct and indirect link between power production and clean water generation. Hence the inclusion/importance given to the energy-water-food (EWF) nexus in the United Nations' sustainable development goals. Acknowledging the importance of decarbonization to the global future, there exists a gap in literature on the development of models that can enhance the EWF nexus, reduce energy poverty, and achieve 100% renewable energy in the electricity sector. Therefore, the technical and economic prospect of geothermal energy for bridging the aforementioned gaps in existing works of literature is presented in this study. The energy poverty/wealthy status of a country has been confirmed to have a significant impact on economic development, as economic development is largely reflected in the food-water availability. Ditto, this study is focused on the interconnectivity of the EWF nexus while incorporating global decarbonization targets. Geothermal energy is of the utmost significance in East Africa due to its abundant potential and distinctive geological features. Located in the Great Rift Valley, the region has an abundance of geothermal reservoirs, making it an ideal location for geothermal power generation. This study is novel as a comprehensive assessment framework for energy poverty is developed and innovative models utilizing primarily the geothermal resource in the East African region to mitigate this problem are proposed and analyzed. The role of hydrogen generation from critical excess electricity production is also analyzed. The East Africa region is considered the case study for implementing the models developed. A central renewable energy grid is proposed/modelled to meet the energy demand for seven East African countries namely; Ethiopia, Tanzania, Uganda, Djibouti, Comoros, Eritrea, and Rwanda. This study considers 2030, 2040, and 2050 as the timestamp for the implementation of the proposed models. The hybrid mix of the biomass power plant, solar photovoltaic (PV), pumped hydro storage system and onshore wind power is considered to furthermore show the potency of renewable energy resources in this region. Results showed that the use of geothermal energy to meet energy demands in the case study will mitigate energy poverty and enhance the region's EWF.

In this work, the biomass fly ash (BFA) supported Ni/La2O3 catalyst was synthesized for the first time to produce syngas, a mixture of CO and H2 via the partial oxidation of methane (POM). The BFA support was modified using laboratory synthesized Ni/La2O3 through the wetness impregnation technique. The Ni/La2O3-BFA catalyst was characterized by several techniques to investigate its suitability for the POM reaction. The characterization results showed that the crystalline structure, better metal support interaction and enhanced thermal stability of Ni/La2O3-BFA make it suitable for the POM. The synthesized Ni/La2O3-BFA catalyst remained stable for 30 h on stream during POM at 850 °C. The addition of La2O3 promoter and active metal Ni to the BFA improved the CH4 conversion from 55% to 85% and enhanced the H2/CO ratio from 1.4 to 2.0 while maintaining a reactants stoichiometric ratio of (CH4:O2 = 2:1). The study of spent catalyst by using various techniques confirmed that the stable catalyst exhibited coke resistance in the POM even after 30 h time on stream. Thus, the performance of BFA supported Ni/La2O3 catalyst shows more potential for catalytic applications due to its suitable physiochemical properties as it is a combination of multiple oxides that synergistically participate in the reaction steps and increases syngas production. It also provides low-cost, abundant, greener, and waste based alternative to expensive metal oxide as supports for catalytic applications.

Over-consumption of limited fossil fuels has caused serious environmental pollution and a global energy crisis, threatening human life and biodiversity. As an ideal, environmentally friendly renewable energy, hydrogen can satisfy human clean energy requirements. Therefore, whether hydrogen can be catalytically generated in the wastewater treatment process is a highly meaningful investigation. Herein, Bi2Te3/Te/C heterojunction nanowires with high specific surface area and rich pore structure were successfully synthesized. The efficient catalytic degradation process is accompanied by the generation of hydrogen. The catalytic degradation of methylene blue and methyl orange was achieved in less than 20 s and 150 s, respectively. Meanwhile, in scaled-up degradation/hydrogen production experiments, fast and efficient H2 production from NaBH4 can be realized in the presence of Bi2Te3/Te/C nanowires. The mechanism of efficient synergistic organic dye degradation and hydrogen production is due to the efficient carrier transfers and accumulation at the hetero-interface. In contrast to previous work, rapid degradation of organic dyes and hydrogen production by decomposition of NaBH4 were achieved without the help of high-cost catalysts such as precious metals. This work could provide an alternative pathway for the future degradation of organic matter in synergistic heterogeneous catalytic wastewater and recovery of by-products including hydrogen.

The production of hydrogen from water is one of the best sustainable energy resources to fulfill the increasing energy deficiency of the world. As most of the available energy resources are harmful in one way or another as nuclear waste is dangerous for human life and burning fossil fuels caused the production of carbon, nitrogen, and Sulphur oxides which increases global warming as well as air pollution. The earth is almost 70% consist of water so that there is need to use this water in efficient way to produce hydrogen as it is more sustainable energy resource and environment friendly. This is an emerging field for researchers and they trying to find the best photocatalyst for hydrogen production. The motivation of this study is to provide improved mechanism for hydrogen production because the developing countries like Pakistan faced serious energy crisis and available energy resources in these countries are the fossil fuels mostly which are not environmentally friendly creating chaos of global warming. The background of this study shows that researcher used doped, composite, and many other different techniques to enhance its efficiency. For the last decade, researchers mainly focused on the doped photocatalyst. In recent decade researcher shifted to composite based photocatalysts. The hypothetical question arises in this study weather these composite useful to improve efficiency of hydrogen production by using photocatalyst method? This review paper especially focuses on different composite photocatalysts for hydrogen production. The composites of Cadmium Sulfite/Titanium dioxide (CdS/TiO2) and Tungsten trioxide/graphite Carbon nitride (WO3/ g-C3N4) have been the main area of interest in this review due to their immense use in research to produce hydrogen. This study will also help to understand the mechanism of the production of hydrogen through water splitting and organic compounds. The study also elaborates on the zigzag (Z) and step (S) schemes used for the photocatalytic activity of composites. Present work showed that composite photocatalyst are better and increased efficiency of hydrogen production because active sites of surface increased. This review will be helpful for new apprentices in this field to understand the basic mechanism, helpful for industrialists and experts to decide which composite photocatalyst is best according to their interests.