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The present article introduces an innovative solution to improve performance efficiency while shaving the demand during peak hours. The idea focuses on efficient gas turbine and Rankine cycle hybridization for power and hydrogen production based on high-temperature heliostat solar towers. The proposed model is simulated via TRNSYS software to assess the performance transiently and then optimized through the artificial neural network in MATLAB program to minimize the calculation time. The key economic, environmental, and energy indicators are evaluated, compared, and optimized for this. According to the effect of main design parameters, including gas turbine inlet temperature, mass flow rate, and heliostat area, on the system's indicators, there is a conflictive trend among the power productivity, cost, and emission index, signifying the optimization significance. The optimization results show that the net power, efficiency, cost, and CO 2 emissions are 298,300 GJ, 30.7%, 3.6 M$, and 20,760 tonnes under optimal conditions. This working condition is obtained by electing turbine inlet temperature, solar area, and airflow rate of 1087 °C, 91,200 m2, and 68,817, respectively. At this condition, while 71.18% of the yearly primary energy is provided by the sun, biomass meets the rest, showing the importance of renewable combination to achieve the highest independence from the grid. Finally, the system can generate an additional 585 kg/day of hydrogen that could be used in relevant industries. • A novel smart system based on biomass and solar hybridization is introduced. • A new hydrogen production/injection method is applied to improve the efficiency. • An artificial neural network model is added to the optimization to reduce the time. • The proposed smart system can generate an extra hydrogen of 585 kg per day. • The optimization achieves an efficiency of 30.7% and emissions of 20,760 tonnes. [ABSTRACT FROM AUTHOR]

The reasonable designing, interfacial tuning and construction of S-scheme heterostructures offering high performance water pollutants treatment and energy production still remains challenging. Following the structure, band structure and interface function perspective, we prepared Fe 7 S 8 /CuIn 5 S 8 heterostructures photocatalysts with sulfur vacancies for superior norfloxacin (NOR) degradation and hydrogen production under visible light. In particular, for optimal 30FS/CIS (30%Fe 7 S 8 /CuIn 5 S 8), the H 2 evolution was up to 35.6 mmol g−1 h−1 which was 11.5 times than pristine Fe 7 S 8 with TEOA as sacrificial agent. The heterojunction could also show 98.7% degradation of NOR in 90 min under visible light. Interestingly, using NOR pollutant as sacrificial agent under synergistic conditions, 22.7 mmol g−1 h−1 H 2 evolution and 98.9% degradation of NOR (in 45 min) was achieved. The significantly boosted photocatalytic pollutant degradation and hydrogen generation performance over Fe 7 S 8 /CuIn 5 S 8 hybrids is ascribed to the efficient S-scheme charge transfer and active sites provided by sulfur vacancies (V s). The deep electron transfer mechanism and the charge transfer efficiency were supported by in-situ XPS, UPS, electrochemical experiments and photoluminescence. Experimental results including scavenging tests and ESR findings provided the direct evidence of photogenerated holes and ●OH radicals for pollutant degradation and electrons in hydrogen generation. This work contributes to effective designing and developing high-activity visible light/solar light assisted heterojunction photocatalysts for realizing superior clean energy generation and pollutant degradation. [Display omitted] • Novel S-scheme Fe 7 S 8 /CuIn 5 S 8 heterostructures successfully constructed. • Synchronous norfloxacin degradation and hydrogen evolution are realized. • The sulfur vacancies promote separation and light absorption. • The photogenerated holes/●OH and electrons are utilized for pollutant degradation and H 2 production. • The photocatalytic mechanism of H 2 evolution and NOR degradation were proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] • The pH-swing cold capture chloralkali process improves energy efficiency threefold over the benchmark process. • Integrating pH-swing cold capture chloralkali in eFuel synthesis moves most of the energy consumption to the electrolyzer. • We attain ∼ 76 % carbon capture efficiency and 79.5 % overall process efficiency. Renewable Fuels of Non-Biological Origin (RFNBOs, a.ka. "eFuels") are drop-in replacements for fossil fuels in the "hard-to-abate" sectors, and utilise existing distribution and storage infrastructure, but suffer from low synthetic efficiency. In particular, the low efficiency and high energy consumption of hydrogen synthesis by freshwater electrolysis remains a problem to be addressed. In the current study, we explore the potential of saltwater electrolysis (chloralkali) for the synthesis of eFuels generally, and specifically eMethanol. The study explores the use of chlorinated water in carbonate-loop pH-swing "cold capture" of carbon dioxide, and the resulting synergetic integration of the chloralkali process in eFuel syntheses. Doing so eliminates the high energy consumption of the calciner and the slaker of the benchmarked carbonate-loop thermal-swing method. It is replaced with a spontaneous chemical process in which chlorine is neutralized in the presence of carbonates. This allows the simultaneous solution of "The Chlorine Problem" of saltwater electrolysis, and a lower overall energy consumption of direct air capture when combined with green hydrogen synthesis. The only limitation on the comparison is that a large amount of carbon dioxide is over-captured when using chloralkali. That is, the ratio of hydrogen generated to carbon dioxide captured is fixed by the stoichiometry of chloralkali and not that of the eFuel. This results in an excess of carbon captured and thus a carbon-negative eFuel. We examine one configuration of secondary revenue and use it to inform the marginal cost of CO 2 capture. In the system proposed by Aeon Blue Technologies (ABT), carbon dioxide is absorbed into caustic according to the standard method. Hydrogen gas is produced in a standard chloralkali electrolyzer, along with caustic for the contactor, and chlorine. Water oxidation by chlorine gives the strong acid, hydrochloric acid, and the weak acid, hypochlorous acid, which react directly with wet carbonate to release CO 2. H 2 and CO 2 react in a methanol reactor to produce eFuel. H 2 is the limiting reagent for eFuel synthesis, giving an excess of cold captured CO 2. Thus, the current study underscores significant advancements in renewable fuel synthesis, particularly eMethanol, and evaluates the carbon capture and energy efficiency of a novel method. The simulation indicates that the marginal energy cost for a tonne of CO 2 is ∼ 184kWh. This gives ∼ 76 % theoretical carbon capture efficiency and an overall process efficiency of 79.5 % (approximately a threefold improvement over the benchmark). The authors are unaware of a comparable method. The overall system yields a tonne of carbon-neutral e-methanol (eMeOH) while capturing an additional 3 tonnes of carbon dioxide, which means the modelled process captures over 300 % more carbon dioxide than is released upon combustion of the eFuel. In summary, this research contributes valuable insights into carbon-negative eFuel production, representing a significant scientific step in sustainable fuel production. [ABSTRACT FROM AUTHOR]

[Display omitted] • Oxygen vacancies fundamentals and importance in photocatalysis. • Oxygen vacancies rich heterojunction-Synthetic strategies. • OVs rich Z-scheme and S-scheme heterojunctions- Photocatalytic mechanism. • Applications for Hydrogen production and water treatment. • The existing challenges and future perspectives. Photocatalytic removal of pollutants and energy production is a green, low cost and environment friendly technology for addressing the mounting pressure of energy crisis and environmental deterioration. Developing efficient photocatalysts is still a big challenge for accelerating the photocatalytic hydrogen production and pollutant degradation especially utilizing solar light. Therefore, constructing oxygen vacancies rich Z-scheme and S-scheme semiconductor heterojunctions emerged as a promising approach to enhance the light harvesting and increasing the redox capability of photocatalysts. This review comprehensively summarises the state of art focus on oxygen vacancy's role in photocatalysts especially in Z-scheme and S-scheme heterojunctions including synthesis process and modifications. In particular, the functions of oxygen vacancy in supporting the main processes in photocatalytic energy production and pollutant removal, such as light absorption, charge separation and conversion are highlighted in this review. The current issues and future prospective in oxygen vacancies rich heterojunctions for efficient photocatalytic removal of pollutant and energy production are also addressed. Finally, a brief discussion on challenges and future prospects is demonstrated. [ABSTRACT FROM AUTHOR]

Membrane reactors are a potential tool to produce high purity hydrogen on-site but sufferfrom immense losses in hydrogen recovery under reaction conditions. For high-temperature operations, these losses mostly occur due to the presence of lesser permeable gases in the reformate that develop into a concentration polarization barrier around the membrane. Based on our previous findings, a multi-pass design was manifested to alleviate hydrogen losses through the membrane tested with synthetic gas mixtures. The same design is currently employed to establish improvement in hydrogen recovery under reaction conditions. Having a catalyst and membrane integrated into a single unit termed as a membrane reactor, its performance is optimized with varying membrane assembly and catalyst bed configurations. This study shows that a packed bed multi-pass membrane reactor is an optimal design to target high hydrogen recovery. Further, multi-pass membrane reactor design also improves the hydrogen recovery in fluidized bed operations which opens immense scope for future studies. [Display omitted] • Methanol fed membrane reactor in a multi-pass reactor design is presented. • Multi-pass reduces concentration polarization barrier effect on hydrogen permeation. • Optimal membrane-gas contacting with multi-pass design improves hydrogen recovery. • Optimally designed packed bed membrane reactor showed best performance. • Multi-pass membrane reactor design improves hydrogen recover. [ABSTRACT FROM AUTHOR]

• g-C 3 N 4 and MOFs based heterojunctions –synthesis routes and advantages. • Types of g-C 3 N 4 and MOFs heterojunctions were discussed-modification strategies. • g-C 3 N 4 and MOFs based heterojunctions for photocatalytic environmental remediation and energy production. • Conclusion and future research prospects on g-C 3 N 4 and MOFs based on heterojunctions. Photocatalytic technology has emerged as a promising solution for environmental remediation and energy production, and the development of efficient and stable photocatalysts is of great importance. Recent advances in g-C 3 N 4 /Metal Organic Frameworks (MOFs) heterojunctions have shown excellent potential in achieving high-performance photocatalytic environmental remediation and energy production. In this review, we have summarized the recent advances in the design and synthesis of g-C 3 N 4 /MOFs heterojunctions and their application in photocatalytic environmental remediation and energy production. We have discussed the advantages and challenges of g-C 3 N 4 /MOFs heterojunctions, such as enhanced light absorption, increased surface area, and improved electron-hole separation, and their effects on photocatalytic performance. We also highlight the recent research progress in the utilization of g-C 3 N 4 /MOFs heterojunctions for various environmental remediation applications, including the degradation of organic pollutants and the removal of heavy metals, as well as for energy production applications such as hydrogen evolution and CO 2 reduction. Furthermore, we provide an overview of the latest theoretical and experimental investigations into the mechanisms of photocatalysis in g-C 3 N 4 /MOFs heterojunctions, which can help to guide the rational design of high-performance photocatalysts. Our analysis of the literature reveals that g-C 3 N 4 /MOF heterojunctions have demonstrated excellent photocatalytic activity for the degradation of various pollutants, such as methyl orange, rhodamine B, and bisphenol A. For instance, a g-C 3 N 4 /ZIF-8 heterojunction achieved a photocatalytic degradation rate of 99.9% for methyl orange under visible light irradiation within 60 min. Moreover, the g-C 3 N 4 /MOF heterojunctions have also been found to be efficient in water splitting for hydrogen production. For instance, a g-C 3 N 4 /UiO-66 heterojunction achieved a hydrogen production rate of 1260 μmol h−1g−1 under visible light irradiation. The recent data on the advances in g-C 3 N 4 /MOFs heterojunctions demonstrate their enormous potential for practical applications in photocatalytic environmental remediation and energy production. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fundamentals of S-scheme and dual S-scheme have been discussed. • Types of heterojunctions are elaborated with mechanism comparisons. • Recent developments in synthetic methods and different morphology of S-scheme and dual S- schemes. • S-scheme and dual S-scheme for photocatalytic environmental remediation and energy production. • Bottlenecks, conclusion and future prospects discussed. Discovering alternative materials and technologies that provide the meaningful potential to environmental and energy-related challenges in critical to the long-term viability of industrial activity and the evolution of society. Photocatalysts are undeniably important, and scientists are working hard to improve their photocatalytic performance. The high recombination rates of photogenerated electron-hole pairs as well as poor redox capability are addressed via heterojunction modification. In this direction, oxidation type and reduction type photocatalysts based S-scheme heterojunctions are highly promising owing to highly diminished recombination facilitated by internal electric field. This review has focused on the shift from Z-scheme to new revolutionary S-scheme based photocatalytic materials with high performance applications in the field of energy and environment. It can be concluded that controllable built-in electric field intensity and stable interfacial carrier transport process make S-scheme heterostrctures ideal. However their application is mainly limited to powder photocatalysts, don't apply to photo-chemistry and solar cells with external circuit, reaction thermodynamics and dynamics management in S-scheme photocatalysts is not adequate. To some extent, dual S-schemes address to these limitations and further research is to be carried out to fight the bottlenecks. Several perspectives on the future of S-scheme and dual S-scheme heterostructure were also provided based on rigorous review of the reported results. A discussion on the previously reported different types of heterojunctions and S-schemes is presented in this review along with plausible charge transfer mechanisms. The synthetic routes to S-scheme heterojunctions are also provided along with modifications and combinations. The current designing and perspective applications in numerous pollutant degradation, hydrogen production and CO 2 conversion is selectively highlighted. The transition of mechanism elucidation from Z-scheme to S-scheme has been discussed with suitable case studies. However, S-scheme heterojunctions designing and fabrication is still new commercially and so present readiness and bottlenecks have been discussed. Hence it is quite imperative for a future roadmap to be laid to design and develop economically viable high performance S-scheme heterojunctions. [ABSTRACT FROM AUTHOR]

The demand for hydrogen in conventional and unconventional oil refining industries is considerable. Currently, the predominant source of hydrogen is from fossil fuel production pathways, in particular, steam methane reforming (SMR), which incurs a significant greenhouse gas (GHG) emissions footprint. Thus, alternative environmentally benign sources of hydrogen will be needed in oil refinery complexes the world over, if their greenhouse gas (GHG) emissions footprint is to be reduced materially. In this paper, an integrated data-intensive techno-economic model is developed to provide a credible estimate of hydropower-hydrogen production costs in Western Canada. The minimum hydrogen production cost for the hydropower-hydrogen plant amounts to $2.43/kg H 2 – this corresponds to an electrolyser farm with 90 units of a 3496 kW (760 Nm 3 /h) rated electrolyser. This cost is competitive with SMR/SMR coupled with carbon capture and sequestration (CCS) production costs, which vary from $1.87/kg H 2 to $2.60/kg H 2 . This point is buttressed by the fact that if existing hydropower plants are used (hence negating hydropower capital costs), the minimum production cost amounts to $1.18/kg H 2 . Hydrogen from hydro power, under the techno-economic conditions considered here, is competitive compared to SMR. [ABSTRACT FROM AUTHOR]

Hydrogen is a key input to industrial processes. In western Canada, there is a significant demand for hydrogen for industrial purposes, both to upgrade bitumen and as a chemical agent. The key driver for this research is the need to assess options for the energy industry to lower its carbon footprint by using hydrogen produced from renewable sources. The environmental impacts associated with hydrogen production through water electrolysis using the electricity generated from a wind power plant are evaluated in this paper. A life cycle assessment was done to determine the greenhouse gas (GHG) emissions per unit mass of produced hydrogen by considering the emissions starting from the extraction of wind energy to the production of hydrogen. An uncertainty analysis was conducted to assess the effects of variations of different input parameters on the GHG footprint of hydrogen produced from wind. The total GHG emissions of a wind-based hydrogen production plant are estimated to be 0.68 ± 0.05 kg CO 2 eq./kg H 2 , 65% of which are from the construction of the wind power system. The results are compared with those of conventional fossil fuel-based systems. The overall GHG emissions from wind-based hydrogen production are about 94% lower than those associated with hydrogen production through steam methane reforming (SMR). Natural gas-based hydrogen production emissions are mainly found in the plant operation stage. For wind-to-hydrogen systems, the manufacturing and installation of the systems have significant environmental impacts. However, the hydrogen produced from wind energy can significantly reduce the GHG footprint of the energy industry. [ABSTRACT FROM AUTHOR]

Hydrogen production via steam methane reforming (SMR) dominates the supply to refining complexes worldwide, resulting in significant greenhouse gas (GHG) emissions. There is a considerable demand for clean hydrogen pathways that are economically competitive with SMR. The development of a 563 MW integrated wind-hydrogen model with energy storage is proposed. The model utilizes real-time wind energy data to ascertain the optimal size of the electrolyser, the number of electrolyser units and the battery (energy storage) capacity that will yield a minimum hydrogen production cost, whilst functioning in a liberalized electricity market with dynamic prices. The optimal plant configuration consists of 81 units of a 3496 kW (760 Nm 3 /hr) electrolyser and 360 MWh (60 units) of battery capacity. For the minimum hydrogen production cost determined ($9.00//kg H 2 ), the wind farm accounts for 63% of this cost. Hence, if existing wind farm assets are used, such that the investment cost of building the wind-hydrogen plant does not include the wind farm costs, the hydrogen production cost is reduced to $3.37/kg H 2 . For a particular electrolyser-battery configuration, it was observed that the minimum hydrogen production cost occurs when their respective capacity factors are approximately equivalent. The benefits of energy storage are limited by the decrease in overall plant efficiency, which results from the use of the battery. For the techno-economic conditions considered in this paper, hydrogen production costs from wind powered electrolysis ($3.37 to $9.00/kg H 2 ) are uncompetitive with SMR/SMR-CCS ($1.87 to $2.60/kg H 2 ). [ABSTRACT FROM AUTHOR]

Western Canada is endowed with considerable reserves of deep un-mineable coal, which can be converted to syngas by means of a gasification process called underground coal gasification (UCG). The syngas can be transformed into hydrogen (H 2 ) through commercially available technologies employed in conventional fossil-fuel based H 2 production pathways. This paper presents a data-intensive model to evaluate life cycle GHG emissions in H 2 production from UCG with and without CCS. Enhanced oil recovery (EOR) was considered as a sequestration method and included in the LCA. The life cycle GHG emissions are calculated to be 0.91 and 18.00 kg-CO 2 -eq/kg-H 2 in H 2 production from UCG with and without CCS, respectively. In addition, a detailed analysis of the influence of key UCG parameters, i.e., H 2 O-to-O 2 injection ratio, ground water influx, and steam-to-carbon ratio in syngas conversion, is completed on the results. The advantage of adopting UCG–CCS technology for H 2 production is realized over the predominant steam methane reforming (SMR) process; around 15.3 million tonnes of GHG emissions can be mitigated to achieve the projected SCO production rate from the bitumen upgrading in 2022. Furthermore, the sensitivity analysis showed that the life cycle GHG emissions is sensitive to the heat exchanger efficiency and the separation efficiency of the pressure swing adsorption (PSA) unit, with increasing values of these parameters causing an increase and a decrease in the magnitude of life cycle GHG emissions, respectively. [ABSTRACT FROM AUTHOR]

Hydrogen (H 2) can play a critical role in global greenhouse gas (GHG) mitigation. Photocatalytic water splitting using solar radiation is a promising H 2 technology. Titanium dioxide (TiO 2) and carbon nitride (g–C 3 N 4)–based photocatalysts are the most widely used photocatalytic materials because of their activity and abundance. Several attempts have been made to improve the photocatalytic performance of these materials in terms of their activity level, life span, response to visible radiation, and stability. However, the environmental impacts of these modifications are often not included in existing studies. This research, therefore, develops a cradle-to-grave life cycle assessment (LCA) framework to evaluate and compare the GHG footprints of four alternative pathways: TiO 2 nanorods and fluorine-doped carbon nitride quantum dots embedded with TiO 2 (CNF: TNR/TiO 2), g-C 3 N 4 , and g-C 3 N 4 /BiOI composite. Unlike most studies that focus only on certain stages such as laboratory-scale photocatalytic fabrication, this study includes utility-scale cell production, assembly, operation, and end of life to give a more accurate and precise environmental performance estimation. The results show that g-C 3 N 4 /BiOI has the lowest GHG footprint (0.38 kg CO 2 eq per kg of H 2) and CNF: TNR/TiO 2 has the lowest energy payback time (0.4 years). In every pathway, energy use in material extraction processes makes up the largest GHG contribution, between 83% and 89%. Sensitivity and uncertainty analyses were conducted under the impact of various input parameters on the life cycle GHG emissions of hydrogen production. Photocatalytic water splitting is highly feasible for adaptation as a mainstream hydrogen production pathway in the future. • LCA of H 2 production via photocatalytic water splitting is conducted. • GHG emissions range from 0.33 to 1.15 kg of CO 2 eq per kg of H 2 produced. • Material extraction has the largest GHG emissions; 56–67% of total emissions. • System is scaled up to produce 5 tonnes of H 2 per day. • H 2 produced has 95% less GHG emissions than steam methane reforming. [ABSTRACT FROM AUTHOR]

Extensive research is being done to develop multifunctional advanced new materials for high performance photocatalytic applications in the field of energy production and environmental detoxification, MXenes have emerged as promising materials for enhancing photocatalytic performance owing to their excellent mechanical properties, appropriate Fermi levels, and adjustability of chemical composition. Numerous experimental and theoretical research works implied that the dimensions of MXenes have a significant impact on their performance. For photocatalysis to thrive in the future, we must understand the current state of the art for MXene in different dimensions. Using MXene co-catalysts in widely used in photocatalytic applications such as CO 2 reduction, hydrogen production and organic pollutant oxidation, this study focuses on the most recent developments in MXenes based materials, structural modifications, innovations in reaction and material engineering. It has been reported that using 5 mg of CdS–MoS 2 -MXene researchers were able to generate as high as 9679 μmol/g/h hydrogen under visible light. The MXenes based heterojunction photocatalyst Co 3 O 4 /MXene was utilized to degrade 95% bisphenol A micro-pollutant in just 7 min. Numerous novel materials, their preparations and performances have been discussed. Depending upon the nature of MXene-based materials, the synthesis techniques and photocatalytic mechanism of MXenes as co-catalyst are also summarized. Finally, some final thoughts and prospects for developing highly efficient MXene-based photocatalysts are provided which will indeed motivate researchers to design novel hybrid materials based on MXenes for sustainable solutions to energy and pollution issues. [Display omitted] • MXenes as new interesting class of photocatalysts. • Composites and heterojunctions with 0D, 1D, 2D, 3D MXenes. • Variable and tunable optical band gaps. • Suitable for energy production and pollution mitigation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel Z-scheme Bi 7 O 9 I 3 /B 4 C heterojunction synthesized by hydrothermal route. • Antibiotic as sacrificial agent- H 2 evolution and antibiotic removal simultaneously. • Antibiotic degradation route and photocatalytic mechanism probed. • Waste to clean energy concept. The dual-function photocatalytic systems with a promising capability for hydrogen evolution and simultaneous pollutant degradation are surely a significant step towards waste-to-energy conversion goals. However, the performance of such photocatalysts is often limited by poor visible-light activity, charge separation and surface reverse reaction involving photogenerated electrons and radicals/intermediates. In this work, we report hydrothermal synthesis of novel Bi 7 O 9 I 3 /B 4 C (BIBC) heterojunction photocatalyst for advanced Norfloxacin antibiotic degradation with simultaneous hydrogen evolution under visible light. In particular, BIBC-30 heterojunction shows H 2 evolution rate of 812 μmol g−1h−1 with simultaneous 94.2% NFN removal which are much higher than bare B 4 C (∼6 times) and Bi 7 O 9 I 3 (∼4 times). Under oxic/aerobic conditions too, a high 456.3 μmol g−1h−1H 2 evolution with nearly complete norfloxacin degradation was achieved. The low band gap of Bi 7 O 9 I 3 and presence of metallic Bio extends the absorbance to NIR region and B 4 C enlarges the surface area of junction along with suppression of the back reaction. It was observed that BIBC heterojunction exhibits manifolds H 2 evolution rate with NFN as sacrificial agent (18.3% apparent quantum efficiency) is manifolds higher than pure water, methanol, triethanolamine and rhodamine B. An effective Z-scheme charge transfer facilitated by Bio is active in the intimately coupled heterojunction with suitably placed energy bands. This work shows that waste to energy conversion can be promisingly achieved by performing H 2 evolution and pollutant removal simultaneously. [ABSTRACT FROM AUTHOR]

• Dual Z-scheme g-C 3 N 4 /Bi 4 Ti 3 O 12 /Bi 4 O 5 I 2 heterojunction by in-situ hydrothermal route. • High performance synergistic H 2 evolution and antibiotic removal under visible light. • Intimately transfer mediated by in-built I 3 −/I− and Bi5+/Bi3+ redox mediator. • h+ and OH radicals as active species for antibiotic degradation-ESR probe. • Antibiotic degradation route and photocatalytic mechanism predicted. Inspired by waste to energy production, we report construction of dual Z-scheme advanced photocatalyst g-C 3 N 4 /Bi 4 Ti 3 O 12 /Bi 4 O 5 I 2 heterojunction for coupled photocatalytic H 2 evolution and degradation of antibiotics with high efficiency. The optimal CTBT-30 i.e (40 %g-C 3 N 4 /Bi 4 Ti 3 O 12)/30 % Bi 4 O 5 I 2 photocatalyst exhibited an excellent rate of H 2 production under visible light (56.2 mmol g−1 h−1) along with simultaneous 87.1 % ofloxacin (OFL) removal. The H 2 production rate is manifolds higher than in ultrapure water, sulfadiazine, rhodamine B and higher in hole scavenging triethanolamine. The interfacial intimate coupling with well-matched energy bands, foster the charge separation with effective Z-scheme transfer facilitated by I 3 −/I− and Bi3+/Bi5+ and redox mediators. The scavenging of majority of holes for direct oxidation or via OH radical formation leaves photogenerated electrons (at CB of g-C 3 N 4 and Bi 4 O 5 I 2) free for H 2 evolution from H 2 O. Such work is promising for designing high photo-absorbing heterojunction photocatalysts for dual functionalities of clean energy production and environmental detoxification. [ABSTRACT FROM AUTHOR]

Gasification has the potential to convert biomass into gaseous mixtures that can be used for hydrogen production. Thermal gasification and supercritical water gasification are commonly used thermochemical methods for conversion of biomass to hydrogen. Supercritical water gasification handles wet biomass, thus eliminating the capital cost-intensive drying step. Thermal gasification is considered as an alternative means of producing hydrogen from microalgae where biomass has to be dried before gasification. The authors developed techno-economic models for assessment of the production of hydrogen through supercritical gasification and thermal gasification processes. Techno-economic assessment was based on developed process models. Equipment was sized and costs were estimated using the developed process models, and the product value was determined assuming 20 years of plant life. The economic assessment of supercritical water and thermal gasification show that 2000 dry tonnes/day plant requires total capital investments of 277.8 M$ and 215.3 M$ for hydrogen product values of $4.59 ± 0.10/kg and $5.66 ± 0.10/kg, respectively. The relatively higher yield obtained in supercritical water gasification compared to thermal gasification results in lower product value of hydrogen for supercritical water gasification, thereby making it more desirable. This cost of hydrogen is about 4 times the cost of hydrogen from natural gas. The sensitivity analysis indicates that biomass cost and yield are the most sensitive parameters in the economics of the supercritical or thermal gasification process; this signifies the importance of algal biomass availability. The techno-economic assessment helps to identify options for the production of hydrogen fuel through these novel technologies. • The production of hydrogen from thermochemical algal conversion is assessed. • Data-intensive techno economic model is developed to determine the product value. • The cost of hydrogen from algal thermochemical processing varies from 4.59 to 5.66 $/kg. • The impact of CO 2 tipping fee on cost of hydrogen was assessed. [ABSTRACT FROM AUTHOR]

• Analyzed H 2 production from a small modular nuclear-powered-electrolysis plant. • Price-following H 2 dispatch model applied in low and high-carbon electricity markets. • H 2 supply cost is from CAD$2.11–2.77/kg in a low-carbon electricity market. • H 2 supply cost is from CAD$1.77–3.36/kg in a high-carbon electricity market. • H 2 from SMNPP-electrolysis can cost-compete with renewable-based H 2 production. Small modular nuclear reactor power plants (SMNRPPs) for hydrogen cogeneration are in early development, and their cost competitiveness for low-temperature electrolysis has not been well-studied. This study combines a quadratically-constrained economic dispatch model and a levelized cost analysis model to evaluate hydrogen cogeneration from a 300 MW SMNRPP coupled with proton exchange membrane electrolyzers. The SMNRPP adjusts its power output based on fluctuating electricity market prices and a time-invariant conversion value for electricity pricing arbitrage. We evaluated the SMNRPP-electrolysis system for 20 years in two case study locations and found the hydrogen supply cost ranged from CAD$1.77–3.36/kg and CAD$2.11–2.77/kg in electricity markets with high and low fossil fuel-dependence, respectively. The SMNRPP-electrolysis system is more cost-effective than fossil fuel-based hydrogen production at CAD$1.54/kg if the SMNRPP capital cost decreases to CAD$4,700/kW. This is because the SMNRPP capital cost accounts for 75% of the hydrogen supply cost variance, while other techno-economic parameters account for less than 27% of the supply cost variance. The system can achieve the lowest cost hydrogen production in under 17 years if the global learning rate and installation growth rates for SMNRPPs exceed 10% and 15%, respectively, to reach a 4.96 GW global footprint. The study outcomes can help formulate policies for SMNRPPs adoption in the hydrogen economy. [ABSTRACT FROM AUTHOR]

• TEA of hydrogen production via photocatalytic water splitting was conducted. • Four earth abundant, active and stable photocatalysts were selected. • The LCOH ranges from 4.15 to 9.8 USD per kg of H 2 produced. • Capital investment and labour costs contribute the most, 75% of the total cost. • The system was scaled from lab to facility to produce 5 tonnes of H 2 per day. Photocatalytic water splitting using solar radiation is among the promising H 2 technologies. Titanium dioxide (TiO 2)- and carbon nitride (g-C 3 N 4)-based photocatalysts are the most widely used photocatalytic materials given their activity under visible light and their abundance. Several attempts have been made to improve the photocatalytic performance of these materials in terms of activity level, life span, response to visible radiation, and stability. However, the economic viability of the large-scale deployment of these modifications is not well evaluated in the existing literature. This study develops a bottom-up techno-economic assessment framework to determine the H 2 production costs in four alternative pathways: TiO 2 nanorods, fluorine-doped carbon nitride quantum dot-embedded TiO 2 (CNF: TNRs/TiO 2), g-C 3 N 4 , and g-C 3 N 4 /BiOI composite. Sensitivity and uncertainty analyses were also conducted to understand the impact of input parameters on the hydrogen production cost. The levelized costs of hydrogen (LCOH) are 4.9 - 0.70 + 0.75 , 5.7 - 0.65 + 0.45 , 5.8 - 1.15 + 0.55 , a n d 7.8 - 0.95 + 0.45 USD per kg of H 2 produced for TNRs, CNF: TNRs, g-C 3 N 4 -S, and BiOI/g-C 3 N 4 -S, respectively. In every pathway, the largest contribution is from capital investment and labour costs; together they make up around 75 % of the total cost. Material cost accounts for 13–29 % of the overall cost. The developed information can help in making investment decisions and policy formulation. [ABSTRACT FROM AUTHOR]

• An integrated, multi-product approach can improve biorefining economics. • The scenario with the highest product offering has the highest return of 13%. • Product prices, feedstock cost, and CAPEX have an impact on the return. • Syngas fermentation is a viable, novel process to valorize biorefinery by-products. The production of multiple products, in an integrated manner, encourages the full valorization of biomass feedstock and reduces waste streams. This may improve the economic outlook of the biorefinery and provide a hedge for investors. There is limited understanding of the techno-economics of an integrated, multi-product biorefinery. This study addresses this gap. In this study, we investigated an integrated, multi-product biorefinery. In addition to bio-oil, the valuable products ethanol and hydrogen are produced from fast pyrolysis by-products. We developed process models for bio-oil, ethanol, and hydrogen production from spruce woodchips in an integrated syngas fermentation and fast pyrolysis plant. Six scenarios set against a base fast pyrolysis plant were investigated, and the economic performance of each scenario was evaluated based on the rate of return. The scenarios differ in terms of the use of the non-condensable gases and the type of external fuel used for process heat. In every scenario, biochar is used for ethanol production and bio-oil is assumed to be a final product. The base case had a return rate of 7.0%, while the return rate ranged between 7.46 and 13.01% among the six scenarios. The scenario producing hydrogen from hydrogen-rich non-condensable gases and ethanol from biochar was the most profitable. The profitability was found to be most sensitive to product prices, capital cost, and feedstock cost. The study's results show that an integrated, multi-product approach to biorefining has the potential to improve the economics of biorefineries and biofuel production. [ABSTRACT FROM AUTHOR]

Electrolytic hydrogen produced from wind and solar energy is considered a long-term option for multi-sectoral decarbonization. The study objective is to develop a framework for assessing country-level hydrogen technical potential from wind and solar energy. We apply locational suitability and zonal statistical analyses methods in a geographic information system-based environment to derive granular insights on non-captive technically exploitable hydrogen potential in high-resource locations. Seven setback factors were considered for locational suitability, and integrated with modules developed for evaluating the wind and solar resource penetration from open-source theoretical renewable resource geospatial data and electricity-to-hydrogen conversion analyses. The technique applied in this study would be a relevant contribution to determining national and regional-wide electrolytic hydrogen production potentials in other jurisdictions with requisite adjustments to data and technical constraints. The results from the case study country, Canada – a major hydrogen-producing country – show that the technical hydrogen potentials from wind and solar energy are approximately 1,897 and 448 million metric tonnes per year, respectively, at least 6.3 times greater than global hydrogen demand in 2019. When we integrated locational data on enabling infrastructure, we discovered that the lack of access to power transmission lines in low-population-density areas of the country significantly reduces the exploitable wind- and solar-based hydrogen potential by over 80% and 6%, respectively. The findings of this study show that in the absence of spatial data on infrastructural constraints, the exploitable hydrogen potential in a jurisdiction can be overestimated, leading to improper guidance for policy and decision-makers. • A framework is developed to determine the H 2 technical potential from solar and wind. • The framework combines locational suitability and zonal statistical analysis in GIS. • A case study analysis was conducted for Canada. • Solar- and wind-based H 2 technical potential is 448 and 1898 Mt/year, respectively. • Low access to enabling infrastructure limits the exploitable potential by over 26%. [ABSTRACT FROM AUTHOR]

This paper presents a model to perform energy balances and estimate hydrogen conversion efficiency from UCG-based syngas. The model was developed for H 2 production from UCG-based syngas with and without CCS, along with the co-production of electricity and steam in a conventional combined cycle plant. In this paper, at base case conditions (H 2 O-to-O 2 injection ratio of 2 and a steam-to-carbon ratio of 3), the coal-to-H 2 conversion efficiency is estimated to be 58.1% for UCG with and without CCS. For the plant configuration involving no CCS, in addition to H 2 production, approximately 4.7% of coal energy is converted to electricity that is exported to the grid. In the case of UCG–CCS, a minor energy penalty is incurred; wherein the electrical energy exported per unit coal energy is around 2.4%, with a CO 2 capture efficiency of 91.6% being achieved. The H 2 conversion efficiency decreases with rise in H 2 O-to-O 2 injection ratio, but increases with fall in steam-to-carbon ratio. Effect of ground water influx in UCG on the H 2 conversion efficiency is minor, whereas H 2 separation efficiency in the pressure swing adsorption (PSA) unit has a major effect. [ABSTRACT FROM AUTHOR]

The demand for hydrogen is likely to increase in the next decade to satisfy the projected growth of the bitumen upgrading industry in western Canada. This paper presents GHG (greenhouse gas) abatement costs and the GHG abatement potential in producing hydrogen from UCG (underground coal gasification) along with CCS (carbon capture and sequestration). Seven hydrogen production scenarios are considered to assess the competitiveness of implementing UCG compared to SMR (steam methane reforming). The analysis is completed through a LCA (life cycle assessment) of large-scale hydrogen production from UCG and SMR with and without CCS. Considering SMR technology without CCS as the base case, the GHG abatement costs of implementing the UCG-CCS technology is calculated to be in the range of 41–109 $CAD/tonne-CO 2 -eq depending on the transportation distance to the CCS site from the UCG-H 2 production plant. Life cycle GHG emissions are higher in UCG than in SMR. The GHG abatement costs for SMR-CCS-based scenarios are higher than for UCG-CCS-based scenarios; they range from 87 to 158 $CAD/tonne-CO 2 -eq in a similar manner to UCG-CCS. Consideration of revenues for selling the CO 2 captured for EOR (enhanced oil recovery) reduces the GHG abatement costs. An opportunity for revenue generation is realized in the UCG-CCS case. [ABSTRACT FROM AUTHOR]

The use of low-carbon hydrogen is being considered to help decarbonize several jurisdictions around the world. There may be opportunities for energy-exporting countries to supply energy-importing countries with a secure source of low-carbon hydrogen. The study objective is to assess the delivered cost of gaseous hydrogen export from Canada (a fossil-resource rich country) to the Asia-Pacific, Europe, and inland destinations in North America. There is a data gap on the feasibility of inter-continental export of hydrogen from an energy-producing jurisdiction to energy-consuming jurisdictions. This study is aimed at addressing this gap and includes an assessment of opportunities across the Pacific Ocean and the Atlantic Ocean, based on fundamental engineering-based models. Techno-economics were used to determine the delivered cost of hydrogen to these destinations. The modelling considers energy, material, and capacity-sizing requirements for a five-stage supply chain comprising hydrogen production with carbon capture and storage, hydrogen pipeline transportation, liquefaction, shipping, and regasification at the destinations. The results show that the delivered cost of hydrogen to inland destinations in North America is between CAD$4.81/kg and CAD$6.03/kg , to the Asia-Pacific from CAD$6.65/kg to CAD$6.99/kg, and at least CAD$8.14/kg for exports to Europe. Delivering hydrogen by blending in existing long-distance natural gas pipelines reduced the delivered cost to inland destinations by 17%. Exporting ammonia to the Asia-Pacific provides cost savings of 28% compared to shipping liquified hydrogen. The developed information may be helpful to policymakers in government and the industry in making informed decisions about international trade of low-carbon hydrogen in both energy-exporting and energy-importing jurisdictions, globally. [Display omitted] • The supply chain cost of H 2 export from Alberta to viable destinations is assessed. • Exporting H 2 to the USA with new long-distance hydrogen pipelines costs 4.81/kg. • Exporting hythane to the USA can reduce H 2 delivered cost to $4.03/kg. • Exporting H 2 to Asia-Pacific and Europe costs $6.65/kg and $8.18/kg, respectively. • Exporting ammonia can reduce the overseas H 2 delivered cost by over 25%. [ABSTRACT FROM AUTHOR]