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CO selective methanation (CO-SMET) is an important method for removing CO from reforming gases. Ru/Al 2 O 3 catalyst prepared by the conventional impregnation method is the most commonly used CO-SMET catalyst and exhibits a spontaneous eggshell-type distribution due to the strong interaction between Ru and Al 2 O 3. The eggshell-type Ru/Al 2 O 3 catalysts exhibited reduced catalytic activity at a high Ru loading due to the agglomeration of Ru at the thin eggshell layer, making it difficult to meet practical CO removal requirements. To address this, four types of acids were individually introduced into the impregnation solutions to weaken the strong interaction between Ru and Al 2 O 3. The prepared catalyst introduced with HNO 3 exhibited a near-uniform distribution and relatively high catalytic activity, but low CO selectivity. Subsequently, a two-step impregnation method was proposed to form a unique distribution. The prepared Ru/Al 2 O 3 catalyst with a Ru loading of 1.5% demonstrated an excellent CO-SMET performance by removing CO to below 10 ppm with a wide temperature range of 213 °C–257 °C, corresponding to CO selectivity ranging from 87.5% to 64.4%. • Conventional Ru/Al 2 O 3 catalysts exhibit spontaneous eggshell-type distribution. • Eggshell-type catalysts exhibit reduced CO-SMET performance at high Ru loading. • Introducing acid in impregnation solution can disrupt eggshell-type distribution. • Two-step impregnated Ru/Al 2 O 3 catalyst exhibits excellent CO-SMET performance. [ABSTRACT FROM AUTHOR]

The CO2 methanation reaction, or Sabatier reaction, is experiencing renewed interest in the context of large‐scale recycling of point CO2 emissions, leading to the power‐to‐gas technology. The reaction represents a flexible route to transform CO2 into methane by hydrogenation with (green) dihydrogen. This exothermic transformation takes place at a reasonable rate at temperatures above 200 °C and is directed to the targeted product at low temperatures. The CO2 methanation nevertheless remains kinetically limited due to the chemical stability of CO2 and the high bond dissociation energy for C═O in CO2. Therefore, the current urgent demand is for the development of catalysts and associated processes with superior activity for CO2 activation at low temperatures. This critical review aims to overview the state of the art of this low‐temperature technology using thermal, plasma and photo‐assisted catalysis. We summarize research advances around low‐temperature CO2 methanation, focusing on catalyst formulations (metal, supports and promoters), reaction mechanisms and suitable activation processes. We discuss each of these critical aspects of the technology and identify the main challenges and opportunities for low temperature (≤200 °C) CO2 methanation. [ABSTRACT FROM AUTHOR]

Catalytic conversion of carbon dioxide (CO2) into value‐added chemicals is of pivotal importance, well the cost of capturing CO2 from dilute atmosphere is super challenge. One promising strategy is combining the adsorption and transformation at one step, such as applying alkali solution that could selectively reduce carbonate (CO32−) as consequences of CO2 adsorption. Due to complexity of this system, the mechanistic details on controlling the hydrogenation have not been investigated in depth. Herein, Ru/TiO2 catalyst was applied as a probe to elucidate the mechanism of CO32− activation, in which with thermodynamic and kinetic investigations, a compact Langmuir‐Hinshelwood reaction model was established which suggests that the overall rate of CO32− hydrogenation was controlled by a specific C−O bond rupture elementary step within HCOO− and the Ru surface was mainly covered by CO32− or HCOO− at independent conditions. This assumption was further supported by negligible kinetic isotope effects (kH/kD≈1), similarity on reaction barriers of CO32− and HCOO− hydrogenation (ΔH≠hydr,Na2CO3 and ΔH≠hydr,HCOONa) and a non‐variation of entropy (ΔS≠hydr≈0). More interestingly, the alkalinity of the solution is certainly like a two sides in a sword and could facilitate the adsorption of CO2 while hold back catalysis during CO32− hydrogenation. [ABSTRACT FROM AUTHOR]

This manuscript discusses the advancements and historical development of solid oxide electrolysis (SOE), co-electrolysis, and methanation technologies, addressing the performance fundamentals and system integration challenges in the context of the EU's 2050 climate neutrality goals. SOE technologies, characterized by their high efficiencies and ability to operate at elevated temperatures, offer significant advantages in hydrogen production and power generation. Co-electrolysis of steam and carbon dioxide in SOEs provides a promising pathway for syngas production, leveraging carbon capture and utilization strategies to mitigate carbon emissions. Additionally, catalytic methanation processes described within facilitate the synthesis of methane from carbon oxides and hydrogen, which could be integral to renewable energy storage and grid-balancing solutions. Historical analysis provides insights into the evolution of these technologies from early experiments to modern applications, including their role in space programmes and potential for industrial scale-up. The current state of research and commercialization, highlighted through various system designs and operational enhancements, suggests that SOEs are crucial for sustainable energy transformations, underscoring the necessity for continued innovation and deployment in relevant sectors. [ABSTRACT FROM AUTHOR]

High‐entropy oxides (HEOs) are an emerging class of materials whose compositional complexity has garnered attention because of their tailorable chemistries and unique properties arising from extreme configurational entropy. Solid‐state methods are often employed to synthesize HEOs, but such methods result in poor material properties for catalytic processes, leaving HEOs less studied for catalysis. Here we utilize different wet‐synthesis strategies to produce porous HEOs and investigate their performance in heterogeneous CO2 hydrogenation to methane. Specifically, HEOs were synthesized using hydrothermal, co‐precipitation, and solvothermal methods, resulting in different morphologies like platelets or spheres. Of the tested materials, HEOs with 2‐D platelets derived from hydrothermally‐synthesized high‐entropy layered double hydroxides had superior catalytic performance, especially in low‐temperature regimes (<300 °C). K‐edge XANES indicated that metallic sites (Ni0‐Co0) were formed during the reaction, and these metallic sites are dispersed into the HEO matrix which is confirmed by STEM/elemental mapping. This facile synthesis approach allows for realized synergy between the metallic sites and the HEO support, leading to superior performance for CO2 methanation compared to low‐entropy counterparts. Finally, this study illustrates how HEOs offer new avenues of tailorability in terms of the interplay between support, active site and reaction temperatures for heterogeneous catalysis. [ABSTRACT FROM AUTHOR]

Poly(heptazine imide) (PHI), one of the crystalline or long‐range ordered allotropes of polymeric carbon nitride, is a promising polymeric photocatalyst; however, preparation of highly crystalline PHI remains a challenge. Herein, through a bottom‐up strategy involving repair of structural defects and increase of specific surface area of melon precursor, we prepared PHI nanorods with dramatically improved long‐range order. The resulting PHI exhibited a shift of product selectivity in CO2 photoreduction from CO to CH4 with a high methanation activity in contrast to the pristine PHI with relatively low long‐range order. The improvement of long‐range order for PHI remarkably enhanced the separation efficiency and transfer kinetics of photogenerated charges as well as the adsorption for *CO intermediate. This study revealed the relationship between the precursor structure and PHI crystal growth in ionothermal synthesis, and also showcased the great potential of highly crystalline PHI in artificial photosynthesis. [ABSTRACT FROM AUTHOR]

Hydrocarbon fuels have caused significant environmental damage, leading to a search for renewable alternatives like hydrogen. The water-gas shift reaction (WGSR) is a key process in hydrogen production, especially in ammonia synthesis. Typically, WGSR occurs in two stages: low-temperature (LT-WGSR) at 180–250 °C and high-temperature (HT-WGSR) at 310–450 °C. Traditional HT-WGSR catalysts use Fe–Cr, but the presence of carcinogenic hexavalent chromium (Cr6+) poses environmental risks, necessitating safer alternatives. This study explores the replacement of chromium with aluminum (Al) and cerium (Ce) in Fe-based catalysts, synthesized via mechanochemical methods. Characterization revealed that Fe–Ce catalysts (85:15 ratio) exhibited superior thermal stability. Additionally, varying nickel (Ni) contents were tested to improve activity, with 10% Ni offering the best performance despite some methane by-products. The study also examined the impact of reduction and calcination temperatures, GHSV, and steam/gas ratios on the catalyst's efficiency. [Display omitted] • The mechanochemical method was used for the preparation of CeO 2 –Fe 2 O 3 support. • The catalytic efficiency of the samples was examined on the high-temperature water gas shift reaction. • The catalyst prepared with CeO 2 showed the best performance compared to those prepared with Al 2 O 3 and Cr 2 O 3. • The Ni (10%) -FeCe catalyst demonstrated the highest efficiency in this process with minimal methane suppression. • The impact of various nickel content and processing conditions was also studied. [ABSTRACT FROM AUTHOR]

An exhaustive review of the available literature regarding the kinetic models for the methanation of COx gases to produce natural gas (CH 4) is reported. Since the oldest and recent reported kinetic studies about this topic were discussed and analyzed. The characteristics of the experimental studies such as the reaction system, operating conditions, catalyst used, and the experimental procedure, as well as the derived reaction rate equations, reaction rate coefficients and activation energies are highlighted. The results of the various kinetic models are also discussed in order to identify appropriate approaches that can be used as reference to develop new kinetic models. Most of the works reported values of reaction order of 0.2–1 and activation energies of 75–110 kJ/mol in a temperature range of 220–450 °C. Average absolute error (ε) values were calculated to evaluate the accuracy of the predicted data, which resulted to be in the range of 0.15 %–8.08 % showing generally a good agreement. • Main reactions that should be considered for kinetic modeling are: methanation of CO 2 and CO, and RWGS. • Using appropriate kinetic model helps define proper operating conditions to produce methane at commercial scale. • LHHW kinetic model is more adequate to represent the COx methanation. [ABSTRACT FROM AUTHOR]

Power‐to‐methane (PtM) offers an efficient opportunity for surplus renewable energy storage, but heat management is a major challenge for conducting the highly exothermic methanation reaction. To address this challenge, this study presents the first successful demonstration of core‐shell catalyst pellets in a pilot‐scale reactor for CO2 methanation. Experiments in a wall‐cooled fixed‐bed reactor are conducted with diluted and undiluted reactant feed under systematic variation of cooling temperature and inlet gas flow rate. The results show that core‐shell catalyst pellets significantly reduce the hot‐spot temperature while maintaining comparable reactant conversions to uncoated catalyst pellets at the same conditions. Additionally, core‐shell catalyst pellets allow for undiluted reactant feed at comparably low hot‐spot temperatures (approx. 600 °C). [ABSTRACT FROM AUTHOR]

The understanding of deactivation processes in heterogeneous catalysis is key for the development of new materials and exploration of new operation windows. In this contribution, the periodic transient kinetic method (PTK) is used to identify and separate catalyst deactivation processes for the first time. The PTK method is applied for a standard Ni/Al2O3 catalyst in CO and CO2 methanation for 24 h and compared to steady‐state experiments. For the example reactions, the study exhibits different deactivation behavior for CO and CO2 methanation. The results demonstrate that the PTK method delivers an insight into the deactivation process and furthermore gives evidence for the underlying mechanism. [ABSTRACT FROM AUTHOR]

The synergies from integrating direct air capture and CO2 methanation are assessed and quantified. Three direct air capture and methanation processes with different integration strategies are proposed: only heat integration, direct air capture sorbent regeneration with high‐pressure H2, and complete integration in a single unit. The heat integration study via pinch analysis evaluated the potential energy demand reduction. Overall autothermal operation is achievable, as the heat generated in methanation often exceeds that required for direct air capture sorbent regeneration. A novel process combining CO2 adsorption and methanation in one reactor provided the best productivity and energy demand results. However, this design requires complex cycles and strict demands on the sorbent and catalyst, requiring further development and experimental demonstration. [ABSTRACT FROM AUTHOR]

This study highlights the significant potential of activated carbon (AC)-based materials in environmental remediation and energy production, particularly in converting carbon dioxide (CO2) and hydrogen (H2) into methane (CH4) and water (H2O) using transition metal-based catalysts. It emphasizes the role of porous AC in waste reduction and resource utilization, examining various applications of CO2 and evaluating environmental impacts. The research explores commercialization opportunities and specifically investigates CO2 methanation using AC-based materials. Using bibliometric analyses of 4196 articles from the Web of Science database, the study identifies a growing research interest in porous AC-related CO2 methanation from 2014 to 2024. The top three journals in this field are Environment Development and Sustainability , Biomass Conversion and Biorefinery , and Journal of Environment Science and Pollution. However, there is limited inter-institutional collaboration in this field, suggesting room for development towards commercializing sustainable CH4 production pathways. CH4 is highlighted as a crucial intermediate in industrial processes, and research directions are identified through co-occurring author keywords analysis. The study suggests the need for a comprehensive approach integrating AC materials into carbon-neutral energy processes while addressing the potential adverse effects of AC nanoparticles on biological and environmental factors. Ultimately, it clarifies the potential uses and commercialization prospects for porous AC materials, especially in conjunction with carbon capture and utilization technologies, promoting sustainable practices in energy production and environmental management. [ABSTRACT FROM AUTHOR]

This study uses the application of Pinch analysis to optimize an integrated electrolyzer and methanation system, a promising approach for producing green hydrogen and synthetic natural gas (SNG). By leveraging renewable energy sources, such as wind and solar, electrolysis is used to produce hydrogen, which reacts with captured carbon dioxide in the methanation reactor to form methane. This process not only allows for efficient energy storage but also supports the reduction of greenhouse gas emissions. A key focus of this study is the optimization of thermal energy flows within the system, which has not been extensively addressed in the literature. Pinch analysis was applied to identify the critical Pinch point, which revealed the temperature at which the most efficient heat recovery could be achieved. The design of a tailored heat exchanger network led to significant improvements, including a 66.45% reduction in hot utility consumption and an 18.85% reduction in cold utility demand. Overall, the system achieved global energy savings of 31.02%. These results were compared with the existing literature, demonstrating that our approach offers comparable or superior utility savings while addressing challenges, such as the complexity of chemical reactions and system integration. This research highlights the potential for substantial operational cost reductions and increasing sustainability in industrial applications, contributing to the advancement of renewable energy technologies and the decarbonization of energy systems. [ABSTRACT FROM AUTHOR]

Increasing energy demand and limited non-renewable energy resources have raised energy security concerns within the European Union. With the EU's commitment to becoming the first climate-neutral continent, transitioning to renewable energy sources has become essential. While wind and solar energy are intermittent, consistent and reliable green energy sources, such as biogas and biomethane, offer promising alternatives. Biogas and biomethane production from biomass address key challenges, including grid stability ("supply on demand"), decentralized energy production, energy density, and efficient storage and transportation via existing natural gas infrastructure. This study examines technologies for converting woody biomass into biomethane and proposes a conceptual design utilizing the best available technologies. The system, situated in Slovenia's Kočevje region—one of Europe's richest forest habitats—was scaled based on the availability of low-quality woody biomass unsuitable for other applications. Combining biomass gasification, catalytic methanation, and biomethanation, supplemented by hydrogen from electrolysis, provides an effective method for converting wood to biomethane. Despite the system's complexity and current technological limitations in energy efficiency, the findings highlight biomethane's potential as a reliable energy carrier for domestic and industrial applications. [ABSTRACT FROM AUTHOR]

The effects of H2O in heterogeneous catalysis of COx (CO2, CO) hydrogenation have been intricate and controversial for many years. On the one hand, H2O molecules and their derivatives (O, H, OH) serve as reactants or co‐reactants, playing a role in modulating the reaction pathway through specific mechanisms. On the other hand, the presence of H2O can influence the catalytic performance by altering the physicochemical properties of the catalyst, such as particle size and chemical state, among others. More importantly, the dual role of H2O leads to both positive and negative outcomes, challenging our understanding of its impact. In this mini review, the relevant research results are summarized in terms of the promoting and inhibiting effects of H2O of the COx hydrogenation reaction (e. g., synthesis of methanol, Fischer‐Tropsch synthesis, methanation, etc.) and discussed from the perspective of catalyst and reaction mechanism, which may provide a certain theoretical basis for the design and development of high‐performance catalysts and referable experience for the further exploration and utilization of H2O effects on related fields as well. [ABSTRACT FROM AUTHOR]

CO2 reduction by sunlight under mild reaction conditions is a research area of increasing interest expected to favor decarbonization and produce fuels and chemicals in the circular economy. We hereby report on the development of a series of titanium oxide‐based solids produced by calcination of MIL‐125(Ti)‐NH2 decorated with RuOx nanoparticles (1 wt %) material at temperatures from 350 to 650 °C and used as photocatalysts for CO2 methanation under simulated sunlight irradiation (45 mW/cm2) at <200 °C and 1.5 atm total pressure. The material synthesized at 350 °C produced the highest photoactivity of the series (4.73 mmol g−1 CH4 at 22 h and an apparent quantum yield at 400, 500 and 750 nm of 0.76, 0.65 and 0.54 %, respectively), comparing favorably with the activities of other MOF‐based materials reported so far. Insights into the material's photocatalytic performance and a study of the possible reaction pathways during CO2 methanation were obtained by electrochemical impedance, electron spin resonance, photoluminescence and in situ FT‐IR spectroscopies together with transient photocurrent and hydrogen temperature programed desorption measurements. The study showed the possibility of using MOF‐based materials as precursors to develop metal oxide photocatalysts with enhanced activities for solar‐driven gaseous CO2 photomethanation. [ABSTRACT FROM AUTHOR]

Thermocatalytic conversions of carbon dioxide (CO2) to value‐added products offer promising approaches to achieving net negative emissions. The catalysts for CO2 conversions, particularly for CO2 hydrogenation reactions, usually involve more than one catalytic sites working together. In this review, we first introduce the advanced characterization techniques used to identify the catalytic sites in CO2 hydrogenation catalysts, sites for hydrogen (H2) activation and CO2 adsorption/activation. We then discuss how the dual or multiple‐site configurations influence the catalytic activity and selectivity in reactions such as reverse water‐gas shift (RWGS), CO2 methanation, and CO2 hydrogenation for methanol (MeOH). We finally explain the Catalytic Sites Contiguity (CSC) concept that our research group developed from the work in CO2 reforming of methane and use it to understand the relationship between the spatial arrangement of catalytic sites and the efficiency of reactant activation and conversion in recent publications on MeOH synthesis from CO2 hydrogenation. We hope our insights into the impact of CSC on catalytic performance lead to a potential top‐down design method in optimizing the CO2 hydrogenation catalysts. [ABSTRACT FROM AUTHOR]

CO 2 methanation has emerged as a promising strategy for the greenhouse gas CO 2 utilization and storage of hydrogen. However, achieving low temperature activity and high temperature stability remains challenging due to the sintering of Ni-based catalysts. To address these limitations, this study introduces a Ni–CaZrO 3 catalyst featuring a perovskite phase supported on ZrO 2 , prepared via citrate complexation and impregnation methods. In this approach, a perovskite-type oxide (PTO) of CaZrO 3 forms through a solid reaction on the surface of ZrO 2 with impregnated CaO. The formation of CaZrO 3 on Ni/ZrO 2 restrains the ZrO 2 support aggregation and reduces the particle size of Ni nanoparticles (NPs), thereby enhancing the activity for CO 2 methanation. The interaction between Ni–CaZrO 3 , and ZrO 2 effectively confines the Ni NPs and CaZrO 3 , enhancing the sintering resistance of Ni–CaZrO 3. This leads to excellent stability of the resulting catalyst for CO 2 methanation. The Ni–CaZrO 3 /ZrO 2 catalyst achieves 85% CO 2 conversion and maintains 100% methane selectivity at 300 °C, demonstrating the prolonged stability over 100 h at 550 °C. Notably, the loading of CaZrO 3 in a perovskite phase on ZrO 2 via solid surface reaction represents an interesting and valuable route, which could be extended to loading other PTOs for industrial applications. [Display omitted] • Ni and CaZrO 3 with perovskite phase loaded on ZrO 2 via solid surface reaction. • Perovskite-type CaZrO 3 reduced Ni particle size and enhanced surface area. • Improved interaction between Ni–CaZrO 3 and ZrO 2 compared to Ni and ZrO 2. • High Ni dispersion achieved 85% CO 2 conversion at 300 °C with 100% CH 4 selectivity. • Ni–CaZrO 3 confinement improved stability over 100 h at 550 °C and anti-sintering. [ABSTRACT FROM AUTHOR]

The global push for sustainable energy solutions has highlighted the importance of producing carbon-zero hydrogen (H 2) directly from petroleum reservoirs. In-situ combustion gasification (ISCG) presents a groundbreaking method to harness the potential of heavy oil reserves for clean hydrogen production. Although simulations have demonstrated the considerable promise of ISCG, the key reactions controlling hydrogen generation require experimental validation, and the underlying mechanisms remain largely unexplored. This research aims to describe the chemical reactions and mechanisms responsible for hydrogen generation during the ISCG of heavy oil. Using a specially designed kinetic cell, we conducted combustion and gasification experiments with heavy oil and coke. The findings revealed that clay minerals in the reservoir sand act as catalysts in the oxidation reactions of heavy oil by shifting reactions to lower temperatures by approximately 20 °C. Hydrogen production began at 450 °C and peaked at 900 °C, with coke gasification and the water-gas shift reaction being the primary mechanisms. Additionally, methane was produced due to hydrogen consumption via methanation reactions, and minerals in the reservoir sands were found to inhibit hydrogen production by increasing hydrogen consumption and methane generation at temperatures above 800 °C. Controlling the reservoir temperature within an optimal range between 450 and 800 °C can enhance hydrogen generation by managing the process mechanisms. This study provides a detailed examination of the ISCG process for heavy oil, paving the way for future development of kinetic models to simulate hydrogen production through ISCG. It also emphasizes the significance of mechanistic control in enhancing hydrogen generation and suppressing hydrogen consumption reactions. • The chemical reactions and mechanisms of H 2 generation via ISCG were described. • H 2 generation is dominated by coke gasification followed by the water gas shift. • H 2 consumption by methanation reactions increases at high temperatures. • Minerals in reservoir sands effect combustion and gasification reactions during ISCG. • H 2 production can be optimized by mechanistic control of the ISCG process. [ABSTRACT FROM AUTHOR]

Nickel-based catalysts are widely studied for water-gas shift (WGS), a key intermediate step in hydrogen production from carbon-based feedstocks. Their viability under practical conditions is limited at high temperatures when Ni aggregates and converts CO to methane, an undesirable side product. Because experimental and computational studies identify undercoordinated Ni step sites as most active toward CH4 formation, we eliminate Ni step sites by atomically dispersing Ni into networked, nanoparticulate CeO2 aerogels. The mesoporous catalyst with 2.5 atomic % Ni in CeO2 is highly active for WGS, converting near-equilibrium levels of CO at 350°C, while no CH4 is detected at the limit of detection (<2 parts per million). In contrast, supporting low weight percentages of Ni clusters or nanoparticles on CeO2 aerogels leads to methanation. The CH4 yield produced by the atomically dispersed Ni-substituted CeO2 aerogel is over an order of magnitude lower than previously reported Ni-based catalysts claiming methane suppression, marking an important advance in the development of WGS catalysts. [ABSTRACT FROM AUTHOR]

Utilizing near zero‐carbon NH3 as fuel in engines is promising for carbon‐neutrality. However, the application of NH3 into the engine suffers from the intrinsic poor combustion characteristics of NH3 and the emission of harmful NOx exhausts. Herein, we proposed and successfully confirmed a novel scenario for converting a conventional “CH4‐fueled” engine to “NH3‐fueled” engine. Specifically, CH4 was used to power the internal combustion engine and release CO2 as the exhaust. Afterwards, we put forward two routes to convert the exhaust and NH3 into N2 and CH4 for enclosing the carbon cycle. The first “spatially decoupled” route splits the exhaust treatment into NH3 cracking over Ru clusters on the calcined Mg−Al hydrotalcite (Ru/MAO) and CO2 methanation over a commercial Ni/Al2O3. Both NH3 and CO2 were almost completely converted into the target products under their respective optimal conditions. The second “spatially coupled” route refers to an one‐pot reaction of NH3 and CO2 into N2, CH4, and H2O. Due to the mismatch of reaction conditions and the competitive adsorption of reactants, the conversions of NH3 and CO2 were lowered to 80.1 % and 49.3 %, respectively, over Ru/MAO under 1 bar (CO2:NH3=3 : 8) at 550 °C. [ABSTRACT FROM AUTHOR]

Developing solid‐solution nano‐alloys from immiscible metals has garnered significant interest; however, the high formation entropy poses substantial challenges in synthesis, hindering a comprehensive understanding of the catalytic mechanisms under alloying effects. Herein, the synthesis of small‐sized (≈2.5 nm) RuxNi1‐x solid‐solution alloy nanoparticles with precisely controlled Ru/Ni ratios across a broad compositional range is reported for the first time, despite their bulk immiscibility. The Ru0.76Ni0.24/TiO2 catalyst, with an optimized Ru/Ni ratio, delivers superior photo‐thermal catalytic activity for CO2 methanation, achieving a CH4 production rate of 3.58 mol gmetal−1 h−1 with 94% selectivity at 250 °C under light irradiation, representing a 2.82‐fold enhancement over monometallic Ru/TiO2. Comprehensive investigations reveal that the reconstruction of electronic structure at Ru–Ni active sites enhances the adsorption/activation of reactants, promotes the transformation of intermediate HCO3* to HCOO*, and facilitates the separation of the photo‐generated charge carriers witnessed by the femtosecond time‐resolved transient absorption (fs‐TA) spectroscopy. These combined effects collectively result in significantly enhanced CH4 formation performance. This work highlights the potential of regulating catalytic sites in immiscible metal combinations for photo‐thermal catalytic CO2 conversion, underscoring the promise of these cost‐effective alloys in heterogeneous catalysis. [ABSTRACT FROM AUTHOR]

Processes that integrate the capture and conversion of CO 2 using dual-function materials (DFMs) exhibit high potential to alleviate global warming. This study reports the numerical analysis of the unsteady-state mass transfer and reactions that occur during CO 2 capture and its hydrogenation to methane in a fixed-bed reactor packed with the DFM (15 wt%Na 2 CO 3 /10 wt%Ni/Al 2 O 3). This study uses thermogravimetric analysis to estimate the reaction rate of the DFM, which is used to predict the mass transfer throughout the reactor. The simulation generally represents the experimental behavior of the reactor fed CO 2 /N 2 and H 2 in sequence. Additionally, the hydrogen flow rate significantly influenced the concentration of the product. The theoretical analysis of the concentration distribution of the chemical species inside the reactor indicates that hydrogen supplied at a low flow rate facilitates the long-term recovery of high concentrations of the product. The results of this study could expedite the practical application of DFM-based processes. • Simulations on a process integrating CO 2 capture and hydrogenation were conducted. • A fixed-bed reactor packed with a dual-function material was analyzed. • Data based on thermogravimetric analysis were used for the numerical analysis model. • Experiments of the reactor fed CO 2 /N 2 and H 2 were well represented by simulations. • Changes in gas composition inside the reactor and at the outlet were predicted. [ABSTRACT FROM AUTHOR]

CO 2 methanation involves the utilization of renewable hydrogen, greenhouse gases CO 2 as raw materials to transform them into clean energy sources in the form of methane. This procedure is of great significance for conserving energy and reducing emissions. In this study, a series of Ni/ZSM-5 catalysts with different Si/Al ratios were prepared. H 2 -TPR and XPS were employed to explore the influence of Al content on the properties of the Ni species. The adsorption properties of the reactants on the different Ni/ZSM-5 catalysts were investigated by CO 2 -TPD and H 2 -TPD. Moreover, as H 2 O is produced during the reaction, contact angle measurement were conducted to investigate the hydrophilicity and hydrophobicity of the samples. It is suggested that the ZSM-5 Si/Al ratio (or Al content) affected both Ni dispersion and catalyst hydrophilicity. The higher Al content in ZSM-5 improved Ni dispersion. However, high hydrophilicity is unfavorable for product removal, leading to poor catalytic performance. As a result, the Ni/ZSM-5 (41) sample with appropriate Si/Al exhibited good catalytic performance with CO 2 conversion of 64 % and CH 4 selectivity of >98 % at 350 °C. The CO 2 conversion and CH 4 selectivity remained at the initial level after reaction for 72 h. This indicates that the Ni/ZSM-5 (41) catalyst has excellent stability. Based on the characterization after the reaction, it can be observed that the catalyst exhibits good carbon deposition resistance and stability. Therefore, the choice of zeolite acid amount is crucial for the reaction performance. This study will provide guideline for the development of high-performance catalysts for CO 2 methanation-loaded Ni. [Display omitted] • The effect of Si/Al ratios on CO 2 methanation over Ni/ZSM-5 was investigated. • The higher Al content in ZSM-5 improved Ni dispersion. • High hydrophilicity is unfavorable for product removal, leading to poor activity. • Ni/ZSM-5 sample with appropriate Si/Al is benefit for good catalytic performance. [ABSTRACT FROM AUTHOR]

Sugarcane bagasse carbon (SCBC) was synthesized and used to support NiCoP/CoP 2 nanoparticles (NiCoP/CoP 2 -SCBC), and its electrocatalytic performance for the hydrogen evolution reaction (HER) was investigated and compared with that of NiCoP/CoP 2 nanoparticles and NiCoP/CoP 2 nanoparticles supported on carbon black (NiCoP/CoP 2 -C). Impressively, NiCoP/CoP 2 -SCBC shows the best electrocatalytic performance for HER with an over-potential of 159.5 mV at 10 mA cm-2 and a Tafel slope of 67.24 mV dec-1, along with the excellent stability. This outstanding performance is partly attributed to the abundant hydroxyl functional groups in SCBC, which can make the catalyst have better dispersion and a higher proportion of Ni2+. In addition, SCBC can lead to more defects in NiCoP/CoP 2 , and SCBC contains a large number of P elements, which can increase the catalytic active sites and contribute to the fast HER process to some degree. • The NiCoP/CoP 2 -SCBC composite catalyst was prepared by a calcination method. • NiCoP/CoP 2 -SCBC shows superior electrocatalytic activity for HER in acid solution. • The high catalytic activity of NiCoP/CoP 2 -SCBC is due to the abundant –OH in SCBC. • More defects caused by SCBC and its rich P content also contribute to the activity. • NiCoP/CoP 2 -SCBC has excellent long-term stability besides high catalytic activity. [ABSTRACT FROM AUTHOR]

Solar light‐driven conversion of CO2 into chemicals with high calorific value is regarded as an upcoming carbon utilization technology for alleviating the energy crisis. This technique faces the challenge of low CO2 conversion and product yield due to charge recombination in the catalyst. In this paper, a dual‐reaction site heterojunction catalyst was designed and fabricated by combining NiO with Bi3O4Br nanosheets, for the separation of CO2 reduction and H2O oxidation semireactions, which effectively promoted electrons and holes separation. The resulting catalyst exhibited a high CH4 production rate (8.12 µmol/g) and selectivity (94.69%). Electron distribution and band structure were investigated to explain the satisfactory catalytic performance. In addition, combining the in‐situ DRIFTS results, a formic acid‐intermediated CO2‐to‐CH4 reaction pathway was proposed. This work aims to pave the way for CH4 production via CO2 photoreduction with high efficiency and selectivity. [ABSTRACT FROM AUTHOR]

In photocatalysis, the resulted heat by the relaxation of most of incident light no longer acts as the industrially favorite driving force back to the target photo‐reaction due to more or less the negative relation between photocatalytic efficiency and temperature. Here, we reported a visible light‐sensitized protocol that completely reversed the negatively temperature‐dependent efficiency in photo‐driven CO2 methanation with saturated water vapor. Uniform Pt/N‐TiO2/PDI self‐assembly material decisively injects the excited electron of PDI sensitizer into N‐TiO2 forming Ti−H hydride which is crucially temperature‐dependent nucleophilic species to dominate CO2 methanation, rather than conventionally separated and trapped electrons on the conductor band. Meanwhile, the ternary composite lifts itself temperature from room temperature to 305.2 °C within 400 s only by the failure excitation upon simulated sunlight of 2.5 W/cm2, and smoothly achieves CO2 methanation with a record number of 4.98 mmol g−1 h−1 rate, compared to less than 0.02 mol g−1 h−1 at classic Pt/N‐TiO2/UV photocatalysis without PDI sensitization. This approach can reuse ~53.9 % of the relaxed heat energy from the incident light thereby allow high‐intensity incident light as strong as possible within a flowing photo‐reactor, opening the most likely gateways to industrialization. [ABSTRACT FROM AUTHOR]

CO2 capture and reduction with H2 (CCR) to synthesise CH4 over dual-functional materials (DFMs) possessing CO2 capture and hydrogenation abilities has recently attracted attention as a promising methodology for utilising low-concentration CO2 in air or exhaust gases without pressure and/or temperature swing operations. Much effort has been devoted to the development of Ni-based DFMs for the CCR of CH4 formation owing to their low cost and high catalytic potential for methanation. However, previous studies have been investigated under relatively high reaction temperatures (400–600 °C) and/or pressurised H2 conditions. In addition, experiments were conducted in the absence of O2 in the simulated CO2 gas. The development of efficient Ni-based DFMs under milder and more realistic reaction conditions is still necessary. In this study, we developed La-modified Al2O3-supported Ni nanoparticles (Ni–La(X)/Al2O3, X denotes the La loading) for the selective formation of CH4 from low-concentration CO2 (1%) in a simulated gas containing O2 (20%). The optimised Ni–La(15)/Al2O3 showed 99% selectivity for CH4 formation under isothermal (350 °C) and non-pressurised conditions. The effect of the La loading amount on the CCR performance was studied using X-ray diffraction, temperature-programmed surface reactions, and steady-state CO2 hydrogenation. Furthermore, the developed Ni–La(15)/Al2O3 was applied to direct capture of ultralow concentration CO2 in air (ambient direct air capture (DAC)) and methanation. [ABSTRACT FROM AUTHOR]

The cement industry is a widely used and energy-consuming sector, making it one of the largest CO 2 emitters, primarily to meet its energy demands. Therefore, this research aims to evaluate the waste heat recovery process from a cement factory to fulfill a portion of its energy requirements. In this study, four scenarios have been evaluated, including power production scenarios, hydrogen production scenarios, methanation production process evaluation scenarios, blending hydrogen with natural gas, oxy-fuel combustion scenarios, and scenarios for producing the required freshwater for the factory and the water electrolysis process. The results show that the steam Rankine cycle with the reheating process and the organic Rankine cycle with methanol working fluid with a production capacity of 24.35 MW, and a payback period of 2.4 years with levelized cost of energy being 0.005809 $/kWh, is the most favorable scenario for the power generation cycle. Also, the process of alkaline electrolysis with a hydrogen production rate of 0.1648 kg/s, and a payback period of 5.816 years, and also with the levelized cost of hydrogen being 1.001 $/kg, happened to be the most suitable hydrogen production scenario compared to other electrolysis scenarios such as PEM and SOEC. Moreover, the process of water desalination by reverse osmosis with the energy consumption of 2.7 MW of power is capable of supplying all the required water of the factory and the water electrolysis process, and it was determined as the most suitable scenario for supplying the required water. • 4E analyses of four power generation scenarios is performed for WHR in cement plants. • Comparing power generation scenarios shows RC with reheating as the most favorable. • Alkaline electrolysis emerges as the top scenario for hydrogen production. • ORC systems with reheating show energy and economic advantages despite lower power. • Reheating in steam RC yields highest power production and economic viability. [ABSTRACT FROM AUTHOR]

The characteristic behavior of the wall exerts a strong influence on the flame acceleration (FA) and deflagration-to-detonation transition (DDT) processes in microchannels [Ramachandran et al., "A numerical investigation of deflagration propagation and transition to detonation in a microchannel with detailed chemistry: Effects of thermal boundary conditions and vitiation," Phys. Fluids 35, 076104 (2023)]. In this work, motivated by the catalytic microcombustors in realistic industrial settings, we study the influence of catalytic nickel walls on the FA & DDT processes. Highly resolved numerical simulations (spanning 10–20 grid points across the flame thickness) are performed, employing a 9-species 21-reaction combustion mechanism for H2-combustion by Li et al. ["An updated comprehensive kinetic model of hydrogen combustion," Int. J. Chem. Kinet. 36, 566–575 (2004)] for the gas-phase chemistry and a 5-species 12-reaction submechanism derived from a methanation microkinetic mechanism by Schmider et al. ["Reaction kinetics of CO and CO2 methanation over nickel," Ind. Eng. Chem. Res. 60, 5792–5805 (2021)] for the catalytic surface chemistry. Stoichiometric H2/air with and without 25% (by mole) of H2O dilution/vitiation are investigated. The simulations demonstrate that catalytic walls enhance flame propagation in the vitiated mixture (which exhibits lower flame speeds) by providing additional radical production and heat release at the surface. As a result, the traditionally observed parabolic-like flame front profile in microchannels inverts due to preferential propagation of the flame along the wall. In contrast, the unvitiated mixture exhibits rapid flame acceleration, and the influence of catalytic walls is found to be minimal. These observations are due to the fact that the residence time available for coupling the heterogeneous wall chemistry with the gas-phase combustion is smaller at higher flame speeds (in unvitiated mixtures). [ABSTRACT FROM AUTHOR]

In this study, we conducted a comparative analysis of the catalytic behavior of Ni-CaO-Al2O3 dual functional material (DFM) and a physical mixture of Ni-Al2O3 and CaO-Al2O3 in the integrated carbon capture methanation (ICCM) process for promoted methane production. H2-temperature-programmed surface reaction (H2-TPSR) analysis revealed that in Ni-CaO-Al2O3 DFM, CO2 adsorbed on the CaO surface can spillover to metallic Ni surface, enabling direct hydrogenation without desorption of CO2. Ni-CaO-Al2O3 DFM exhibited a rapid initial methanation rate due to CO2 spillover. The Ni-CaO-Al2O3 DFM, with Ni and CO2 adsorption sites in close distance, allows efficient utilization of the heat generated by methanation to desorb strongly adsorbed CO2, leading to enhanced methane production. Consequently, Ni-CaO-Al2O3 DFM produced 1.3 mmol/gNi of methane at 300 °C, converting 35% of the adsorbed CO2 to methane. [ABSTRACT FROM AUTHOR]

Several Cu and Ni-based catalysts were synthetized over Ce-based supports, either pure or mixed with different amounts of alumina (1:2 and 1:3 mol/mol). Different metal loadings (10–40 wt%) and preparation methods (wet impregnation, co-precipitation, and flame-spray pyrolysis—FSP) were compared for the oxidative steam reforming of methanol. Characterization of the catalysts has been performed, e.g., through XRD, BET, XPS, TPR, SEM, and EDX analyses. All the catalysts have been tested in a bench-scale continuous setup. The hydrogen yield and methanol conversion obtained have been correlated with the operating conditions, metal content, crystallinity of the catalyst particles, total surface area, and with the interaction of the metal with the support. A Cu loading of 20% wt/wt was optimal, while the presence of alumina was not beneficial, decreasing catalyst activity at low temperatures compared with catalysts supported on pure CeO2. Ni-based catalysts were a possible alternative, but the activity towards the methanation reaction at relatively high temperatures decreased inevitably the hydrogen yield. Durability and deactivation tests showed that the best-performing catalyst, 20% wt. Cu/CeO2 prepared through coprecipitation was stable for a long period of time. Full methanol conversion was achieved at 280 °C, and the highest yield of H2 was ca. 80% at 340 °C, higher than the literature data. [ABSTRACT FROM AUTHOR]

Efficient heterogeneous catalyst design primarily focuses on engineering the active sites or supports, often neglecting the impact of trace impurities on catalytic performance. Herein, we demonstrate that even trace amounts of sulfate (SO42−) residuals on Ru/TiO2 can totally change the CO2 reduction from methanation to reverse-water gas shift (RWGS) reaction under atmospheric pressure. We reveal that air annealing causes the trace amount of SO42− to migrate from TiO2 to Ru/TiO2 interface, leading to the significant changes in product selectivity from CH4 to CO. Detailed characterizations and DFT calculations show that the sulfate at Ru/TiO2 interface notably enhances the H transfer from Ru particles to the TiO2 support, weakening the CO intermediate activation on Ru particles and inhibiting the further hydrogenation of CO to CH4. This discovery highlights the vital role of trace impurities in CO2 hydrogenation reaction, and also provides broad implications for the design and development of more efficient and selective heterogeneous catalysts. The impact of trace impurities on catalytic performance is often overlooked. Here the authors show that trace amounts of sulfate residuals on Ru/TiO2 substantially enhance hydrogen transfer from Ru particles to the TiO2 support, shifting CO2 reduction from methanation to the reverse water-gas shift reaction. [ABSTRACT FROM AUTHOR]

In an FP-PEMFC system vent, recycling a fraction of CO 2 provides clear benefits for CO 2 utilization and rejected H 2 conversion to methane. However, the low H 2 /CO 2 ratio, deviating from the ideal stoichiometric value, presents challenges. This study examines the effects of temperature, H 2 /CO 2 ratio, residence time (F/W cat ratio), and La promoter loading on CO 2 and H 2 conversions and CH 4 selectivity over Ni–La/γ-Al 2 O 3 catalyst using a Box-Behnken design. Experimentally, higher CO 2 conversion is observed with increased temperature, H 2 /CO 2 , La loading, and reduced F/W. CH 4 selectivity, however, decreases with higher temperature and F/W but improves with higher H 2 /CO 2 and La loading. Modeling highlighted significant interactions, revealing two optimal conditions: for low La loading, high temperature, H 2 /CO 2 , and F/W are favorable; for high La loading, lower temperature and F/W, coupled with a high H 2 /CO 2 , are optimal. These findings necessitate precise control over input factors, especially H 2 /CO 2 , in optimizing methanation under low H 2 /CO 2 conditions. [Display omitted] • Effective CO 2 methanation with low H 2 /CO 2 ratios and optimal catalyst conditions. • Finding complex interaction where traditional kinetic models struggle. • Nonlinear and combined effects of temperature, La loading and/or F/W. • Combined optimization of catalyst formulation and reaction conditions. • Crucial use of RSM unraveling complex relationship for combined input optimization. [ABSTRACT FROM AUTHOR]

The conversion of CO2‐H2 mixtures on Ni‐based catalysts can proceed through either the reverse water gas shift reaction (RWGS) path to produce CO or the CO2 methanation path to produce CH4. The balance between these competing reactions depends on both the reaction conditions and catalyst structure. In this study, using surface‐sensitive infrared and ambient pressure X‐ray photoelectron spectroscopies, we investigate the effect of reaction conditions on the interaction between CO2 and H2 on a Ni(111) model catalyst. Our findings highlight the occurrence of RWGS, involving direct dissociation of CO2 to CO and atomic oxygen, followed by oxygen reacting with hydrogen to form H2O, and CO and H2O desorption. Hydrogen affects the distribution of CO between hollow and top sites by displacing oxygen from the energetically preferred hollow sites. The overall balance between oxygen production from CO2 dissociation and oxygen removal by hydrogen governs the oxygen coverage and consequently the distribution of CO between top and hollow sites. This balance is significantly influenced by the reaction temperature and the H2/CO2 partial pressures. [ABSTRACT FROM AUTHOR]

CO2 hydrogenation to methane, namely, CO2 methanation or Sabatier reaction, is a significant approach to convert CO2 and H2 to storable and transportable CH4. Low reaction temperature is the key to industrialization and has attracted plenty of research interest. Ni-based catalysts are commonly utilized owing to their favorable properties of excellent activity and economical price. However, it is still challenging to perform the Sabatier reaction under temperatures lower than 300 °C owing to the inertness of CO2. Hence, in this article, we summarize the advances of four important design principles of the Ni-based catalysts for low-temperature Sabatier reaction, namely, optimizing Ni active sites, tuning support properties, considering metal–support interactions, and choosing a suitable preparation method, which provides deep insights for the design of low-temperature CO2 methanation catalysts. Additionally, typical low-temperature CO2 methanation reaction mechanisms with *CO or *HCOO as the main intermediate and perspectives on this topic have been provided. We highlight that the rare-earth oxide-supported Ni-based catalysts with the potential reaction mechanism and corresponding reactor design would be promising for low-temperature Sabatier reaction. [ABSTRACT FROM AUTHOR]

Nickel oxide (NiO) is one of the most popular hydrogenation catalysts. In heterogeneous catalysis, nickel oxide is used, for example, as a suitable methanation catalyst in the Fischer–Tropsch reaction not only for CO hydrogenation but also in the modified Fischer–Tropsch reaction with CO2. However, CH4 selectivity and CO2 conversion strongly depend on NiO micro- (MPs) and nanoparticles' (NPs) shape, size, and surface area. In this study, the synthesis of NiO micro- and nanoparticles was conducted using the simple solvothermal method. Different morphologies (microspheres, sheet clusters, hexagonal microparticles, and nanodiscs) were prepared using this method with different solvents and stabilizers. The prepared catalysts were tested in the hydrogenation of CO2 in a gas phase with excellent conversion values and high selectivity to produce CH4. The best results were obtained with the NiO with disc or sphere morphology, which produced methane with selectivity at a level near 100% and conversion close to 90%. [ABSTRACT FROM AUTHOR]

Herein, a Mott-Schottky heterojunction catalyst was developed by incorporating nickel (Ni) nanometallic particles supported on nitrogen-doped carbon-coated TiO 2 , enabling full-spectrum light absorption and facilitating a robust metal-support interface. This catalyst demonstrated exceptional performance in photo-thermal catalysis. Specifically, the Ni/0.5-TiO 2 @NC catalyst achieved a CO 2 hydrogenation rate of 65.3 mmol/(g cat ·h) with a CH 4 selectivity exceeding 99% under full-spectrum illumination. Remarkably, the catalyst exhibited excellent stability, maintaining its performance over two reaction cycles. The strong metal-support interface of the Mott-Schottky heterojunction catalyst enhanced photo-generated electron-hole separation efficiencies, leading to a substantial rise in catalyst surface temperature. Consequently, this phenomenon accelerated the reaction kinetics and lowered the activation energy, thereby improving overall efficiency. [Display omitted] • Mott-Schottky heterojunctions consisting of TiO 2 @NC-support and highly dispersed Ni NPs catalysts were successfully prepared. • The Mott-Schottky heterojunction catalysts exhibit rapid interface electron transfer, leading to superb carrier separation efficiencies. • The Ni/0.5-TiO 2 @NC catalyst demonstrates exceptional photo-thermal co-catalytic effects, resulting in outstanding performance in the RWGS reaction. • The in-situ DRIFTS analysis revealed that the mechanism governing the photo-thermal co-catalytic RWGS reaction follows the *HCOO pathway. Photo-thermal co-catalytic reduction of CO 2 to synthesize value-added chemicals presents a promising approach to addressing environmental issues. Nevertheless, traditional catalysts exhibit low light utilization efficiency, leading to the generation of a reduced number of electron-hole pairs and rapid recombination, thereby limiting catalytic performance enhancement. Herein, a Mott-Schottky heterojunction catalyst was developed by incorporating nitrogen-doped carbon coated TiO 2 supported nickel (Ni) nanometallic particles (Ni/x-TiO 2 @NC). The optimal Ni/0.5-TiO 2 @NC sample displayed a conversion rate of 71.6 % and a methane (CH 4) production rate of 65.3 mmol/(g cat ·h) during photo-thermal co-catalytic CO 2 methanation under full-spectrum illumination, with a CH 4 selectivity exceeding 99.6 %. The catalyst demonstrates good stability as it shows no decay after two reaction cycles. The Mott-Schottky heterojunction catalysts display excellent efficiency in separating photo-generated electron-hole pairs and elevate the catalysts' temperature, thus accelerating the reaction rate. The in-situ experiments revealed that light-induced electron transfer effectively facilitates H 2 dissociation and enhances surface defects, thereby promoting CO 2 adsorption. This study introduces a novel approach for developing photo-thermal catalysts for CO 2 reduction, aiming to enhance solar energy utilization and facilitate interface electron transfer. [ABSTRACT FROM AUTHOR]

Biogas offers significant benefits as a renewable energy source, contributing to decarbonization, waste management, and economic development. This comprehensive review examines the historical, technological, economic, and global aspects of biomethane production, focusing on the key players such as China, the European Union, and North America, and associated opportunities and challenges as well as future prospects from an Australia perspective. The review begins with an introduction to biogas, detailing its composition, feedstock sources, historical development, and anaerobic digestion (AD) process. Subsequently, it delves into major biomethane production technologies, including physicochemical absorption, high‐pressure water scrubbing (HPWS), amine scrubbing (AS), pressure swing adsorption (PSA), membrane permeation/separation (MP), and other technologies including organic solvent scrubbing and cryogenic separation. The study also discusses general guidelines of techno‐economic assessments (TEAs) regarding biomethane production, outlining the methodologies, inventory analysis, environmental life cycle assessment (LCA), and estimated production costs. Challenges and opportunities of biogas utilization in Australia are explored, highlighting and referencing global projections, polarization in production approaches, circularity in waste management, and specific considerations for Australia. The review concludes discussing future perspectives for biomethane, emphasizing the importance of technological advancements, policy support, and investment in realizing its full potential for sustainable energy and waste management solutions. [ABSTRACT FROM AUTHOR]