High Methane Selectivity Research Articles

Engineering nanoparticle structure at synergistic Ru-Na interface for integrated CO2 capture and hydrogenation

The development of dual functional material for cyclic CO2 capture and hydrogenation is of great significance for converting diluted CO2 into valuable fuels, but suffers from kinetic limitation and deactivation of adsorbent and catalyst. Herein, we engineered a series of RuNa/γ-Al2O3 materials, varying the size of ruthenium from single atoms to clusters/nanoparticles. The coordination environment and structure sensitivity of ruthenium were quantitatively investigated at atomic scale. Our findings reveal that the reduced Ru nanoparticles, approximately 7.1 nm in diameter with a Ru-Ru coordination number of 5.9, exhibit high methane formation activity and selectivity at 340 °C. The Ru-Na interfacial sites facilitate CO2 migration through a deoxygenation pathway, involving carbonate dissociation, carbonyl formation, and hydrogenation. In-situ experiments and theoretical calculations show that stable carbonyl intermediates on metallic Ru nanoparticles facilitate heterolytic C–O scission and C–H bonding, significantly lowering the energy barrier for activating stored CO2.

Alumina lattice confined Niσ+ species as highly selective and anti-coking sites for sustainable propane dehydrogenation

Propane dehydrogenation (PDH) is a vital petrochemical process. As an alternative to Pt and Cr-based catalysts, Ni-based catalysts used in PDH, however, exhibit low propylene selectivity with severe coking. This work aims to understand the role of different Ni species in PDH and achieve high propylene selectivity by inhibiting coking. Specifically, we obtained NiOx/Al2O3 catalysts with solely tetrahedrally coordinated Ni2+ (NiIV) by selectively removing microcrystalline NiOx using the impregnation-complexation strategy. The Niσ+ species derived from NiIV exhibited high propylene selectivity (∼88 %) and low coke yield (2.26 %) in PDH. In contrast, reducing microcrystalline NiOx to Ni0 resulted in high methane selectivity and high coke yield (14.90 %). Theoretical calculations and experimental results indicate that this difference is attributed to the faster propylene desorption from Niσ+ as compared to that from Ni0. Therefore, catalysts with well-confined Niσ+ are selective in PDH. This study offers a rational strategy for designing Ni-based PDH catalysts.

Effect and mechanism of ionic liquid-polymer composite coating on enhancing hydrogen embrittlement resistance of X80 pipeline steel for hydrogen blended natural gas transportation

Blending hydrogen into existing natural gas pipelines is a cost-effective method for large-scale hydrogen transportation. However, high hydrogen ratios cause hydrogen embrittlement in pipeline steel, limiting transportation efficiency. Due to complex structures and harsh application conditions, existing coatings are difficult to apply on pipelines. To tackle such issues, we propose an ionic liquid-polymer composite coating using epoxy resin as coating substrate, based on the competitive adsorption of methane and hydrogen on pipeline steel. Ionic liquids with high methane selectivity were selected via quantum chemical calculation. The protective effect of coatings was characterized using hydrogen pre-charging constant strain tensile tests. Simulation and experimental results demonstrate that epoxy resin coatings reduce hydrogen embrittlement in X80 steel. Modified with selective CH4/H2 permeability ionic liquids, the epoxy resin coating enhances methane and hydrogen competitive adsorption on the steel surface, improving hydrogen embrittlement resistance. This novel coating offers a viable solution for achieving safe and high ratio hydrogen blended transportation in natural gas pipeline.

CO2 methanation over low-loaded Ni-M, Ru-M (M = Co, Mn) catalysts supported on CeO2 and SiC

The concentration of the major greenhouse gas CO2 is rapidly increasing in the atmosphere, leading to global warming and a range of environmental issues. An efficient circulation and utilization of CO2 is critical in the current environmental context. Methanation, an exothermic process, emerges as a critical strategy for effective CO2 utilization. On this front, there is a significant demand for rational design of catalysts that maintain high activity and methane selectivity over a wide temperature range (250–550 °C). The catalyst that can promise a consistent reaction even at 500 °C under an atmospheric pressure is thus obliged. The present study investigated bimetallic catalysts with SiC, which is known for its exceptional thermal conductivity, and CeO2, which is characterized by its CO₂ affinity, as base materials. We incorporated Ni-M and Ru-M (M = Co and Mn) as the active metals, each loaded at 2 %. Impressively, with merely 20 mg, the Ni-Co/SiC catalyst achieved a CO2 conversion rate of 77 % and CH₄ selectivity of 88 % at 500 °C, in a fixed-bed tubular reactor system with conditions of H2/CO2 = 4, a total flow rate of 70 ml min−1, and a steady GHSV of 12,000 h−1. Moreover, 2Ni-2Co/CeO2 catalyst demonstrated exceptional performance with a 76 % conversion of CO2 and a 83 % selectivity for CH4, all under identical conditions. The catalyst's durability was confirmed by a subsequent 40-hour stability test, which showed only a 3–5 % degradation. The developed catalysts were comprehensively characterized by BET/BJH, CO pulse chemisorption, H2-TPR, HAADF-STEM-EDS, SEM-EDS and XRD etc. to unveil their physicochemical and surface traits. It was found that Co and Mn, when integrated, effectively restrained the agglomeration of Ni and Ru particles, ensuring optimal metal dispersion on the support. In conclusion, our synthesized bimetallic catalysts shown a sustained catalytic capability, even in the high-temperature environment.

Preparation of Ni/YSZ Catalysts for Application of Solid Oxide Electrolysis Cell Methanation

Co-electrolysis of CO2 and steam using solid oxide electrolysis cells (SOECs) is a major focus of the CO2 conversion. Furthermore, SOECs have the potential to drive high value-added products with reduced carbon footprint. For example, the syngas (mixture of CO and H2) can be produced by SOEC-driven co-electrolysis of CO2 and steam, and utilized in the Fischer-Tropsch (FT) process for the synthesis of artificial hydrocarbon. The artificial hydrocarbons would be environmentally friendly fuels when CO2 is obtained from carbon capture and storage (CCS) technology. The Ni-based cermet, such as Ni with yttria-stabilized zirconia (Ni/YSZ), is a typical material of SOEC device, and Ni has been found to be an active catalyst for CH4 production (methanation). Therefore, use of the Ni/YSZ has potential to directly convert CO2 and H2O to CH4. In the catalytic process, the activity, selectivity and durability of the Ni/YSZ catalyst are significantly influenced by the structural property of Ni and YSZ, which is varied by the Ni loading and calcination conditions in addition to the studied reaction conditions. The preparation of Ni/YZS catalyst with high performance in co-electrolysis and methanation is still challenging.Herein, the preparation of the Ni/YSZ catalysts with enhanced activity in SOEC methanation was studied. The Ni/YSZ catalysts were prepared by wet impregnation, one of the catalyst preparation methods, and characterized by several conventional methods. Effects of Ni loading and calcination conditions on the performance of Ni/YSZ catalysts were examined by CO2 methanation. A Ni/YZS catalyst gave a high CO2 conversion of 86% and a high methane selectivity at around 300 ºC under ambient pressure. With Ni/YSZ prepared using the optimized method, we are planning to prepare tubular cells and evaluate their activity in SOEC methanation.

Elemental Fe conditioning for the synthesis of highly selective and stable high entropy catalysts for CO2 methanation

High entropy oxides (HEOs) with high stability and designability have demonstrated excellent catalytic performance in CO2 hydrogenation. However, it is challenging to combine high methane selectivity and high stability of HEOs using an equimolar design strategy. In this study, a non-equimolar design strategy was used to fix the Cr, Co, Mn and Ni elements and adjust different Fe molar amounts to prepare a highly crystalline HEO at 900 °C. After H2 reduction, the catalyst (HEO-4-900/H2) achieved 72.9% CO2 conversion and 98.8% methane selectivity at atmospheric pressure and 400 °C, and maintained a high methane selectivity of over 97% after 100 h stability test. The catalytic activity was influenced by the amount of Fe. Increasing the amount of Fe could precisely regulate the crystallinity and oxygen defects of the crystal, improve the catalyst stability, reduce the interaction between the Co-Ni alloys and HEOs, and allow the catalyst to contain more Co-Ni active sites and more abundant oxygen vacancies. This study demonstrates the considerable potential of HEOs for CO2 methanation, and provides a new design idea for further stimulating highly active CO2 methanation HEOs catalysts.

Cerium‐promoted Ni/SiO2 catalyst for CO methanation

AbstractCe‐promoted Ni catalysts were developed and applied in a CO methanation reaction. The 10%Ni/SiO2 catalyst exhibits poor initial CO conversion (32.8%) and rapid deactivation with the highest methane selectivity during CO the methanation reaction. In contrast, the 4%Ce–10%Ni/SiO2 catalyst shows dramatically increased initial CO conversion, which is up to 90.7%. Additionally, the apparent activation energy, Ea value, of 4%Ce–10%Ni/SiO2 was calculated to be 102.2 kJ/mol according to the Arrhenius equation, which is much lower than that of the 10%Ni/SiO2 catalyst, which was 139.1 kJ/mol. Based on various characterization results, it is found that the added Ce significantly improves the dispersion of the supported nickel, suppresses the sintering of nickel particles, and forms more adsorbed CO species of three‐fold carbonyl species, resulting in higher CO conversion and good stability during the CO methanation reaction.

Preparation of Ni/YSZ Catalysts for Application of Solid Oxide Electrolysis Cell Methanation

Combination of co-electrolysis of CO2 and steam using solid oxide electrolysis cells (SOECs) and methane production (methanation) offers an attractive process for CO2 conversion to hydrocarbon fuels. Ni-based (Ni/YSZ is a typical example) SOECs could be used as catalytic reactor for CH4 production because Ni has been found to be an active catalyst for methanation. Therefore, Ni/YSZ SOECs could be used as catalytic reactor for methanation. Based on this concept, in this study we have prepared a Ni/YSZ material that can be used in the catalytic reactor. The performance of the prepared Ni/YSZ was evaluated as a catalyst for CO2 methanation. Ni/YSZ catalysts with a Ni loading of 55wt% calcined at 800-1100 ºC gave a high CO2 conversion of up to 86% and a high methane selectivity of >99% at 250-350 ºC of reaction temperature under ambient pressure.

Preparation of cobalt-ruthenium nanocatalysts supported on nitrogen-doped graphene aerogel and carbon nanotubes in Fischer-Tropsch synthesis

In this study, cobalt-ruthenium nanocatalysts supported on nitrogen-doped graphene aerogel (NGA) and carbon nanotubes (CNT) were synthesized using the wet impregnation method for Fischer-Tropsch process with a cobalt to ruthenium ratio of 1:50. The synthesized catalysts underwent various characterizations such as FTIR, ICP, BET, XRD, EDX, TPR and TEM. The performance of the synthesized catalysts was compared to that of a cobalt-ruthenium nanostructured catalyst supported on NGA and CNTs. The catalysts were evaluated in a fixed-bed reactor at 25 bar, with a gas ratio H2/CO: 2 and Gas Hourly Space Velocity (GHSV) 10,000 mlg-1h-1, at temperatures of 260 °C and 280 °C. The use of NGA as a cobalt catalyst support led to a 70.5% conversion of carbon monoxide and higher methane selectivity. Conversely, the use of CNTs led to 63.7% conversion of carbon monoxide and higher selectivity towards C5+ production.

From Lab to Technical CO2 Hydrogenation Catalysts: Understanding PdZn Decomposition.

The valorization of CO2 to produce high-value chemicals, such as methanol and hydrocarbons, represents key technology in the future net-zero society. Herein, we report further investigation of a PdZn/ZrO2 + SAPO-34 catalyst for conversion of CO2 and H2 into propane, already presented in a previous work. The focus of this contribution is on the scale up of this catalyst. In particular, we explored the effect of mixing (1:1 mass ratio) and shaping the two catalyst functions into tablets and extrudates using an alumina binder. Their catalytic performance was correlated with structural and spectroscopic characteristics using methods such as FT-IR and X-ray absorption spectroscopy. The two scaled-up bifunctional catalysts demonstrated worse performance than a 1:1 mass physical mixture of the two individual components. Indeed, we demonstrated that the preparation negatively affects the element distribution. The physical mixture is featured by the presence of a PdZn alloy, as demonstrated by our previous work on this sample and high hydrocarbon selectivity among products. For both tablets and extrudates, the characterization showed Zn migration to produce Zn aluminates from the alumina binder phase upon reduction. Moreover, the extrudates showed a remarkable higher amount of Zn aluminates before the activation rather than the tablets. Comparing tablets and extrudates with the physical mixture, no PdZn alloy was observed after activation and only the extrudates showed the presence of metallic Pd. Due to the Zn migration, SAPO-34 poisoning and subsequent deactivation of the catalyst could not be excluded. These findings corroborated the catalytic results: Zn aluminate formation and Pd0 separation could be responsible for the decrease of the catalytic activity of the extrudates, featured by high methane selectivity and unconverted methanol, while tablets displayed reduced methanol conversion to hydrocarbons mainly attributed to the partial deactivation of the SAPO-34.

Enhancement of Fischer-Tropsch Synthesis by Periodical Draining of the Wax-Filled Pores of a Cobalt Catalyst by Hydrogenolysis

Fischer-Tropsch reactors operated in a steady state suffer from a low pore effectiveness factor and a high methane selectivity caused by internal mass transfer limitations due to the accumulation of long-chain hydrocarbons inside the catalyst pores. Therefore, an alternating process switching between Fischer-Tropsch synthesis (FTS) and drainage of the pores by hydrogenolysis is proposed. The periodical cracking of the accumulated waxes within the (partially) filled pores, realized by a switch from syngas (H<sub>2</sub>, CO) to pure hydrogen, results in a higher overall catalyst productivity and a more favorable product distribution. The influence of temperature and time of FTS on drainage time and product distribution was experimentally investigated at typical temperatures of FT fixed bed processes in a range of 210 to 240°C. Alternating drainage of the pores by hydrogenolysis at a hydrogen partial pressure of just 1 bar leads to an improvement of the rate of CO conversion by up to 90% (240°C, 2 h FTS) and an improvement of even 120% concerning the rate of production of non-methane hydrocarbons (240°C, 2 h FTS).

Effective synergies in indium oxide loaded with zirconia mixed with silicoaluminophosphate molecular sieve number 34 catalysts for carbon dioxide hydrogenation to lower olefins

Tandem catalysts consisting of metal oxides and zeolites have been widely studied for catalytic carbon dioxide (CO2) hydrogenation to lower olefins, while the synergies of two components and their influence on the catalytic performance are still unclear. In this study, the composite catalysts composed of indium oxide loaded with zirconia (In2O3/ZrO2) and silicoaluminophosphate molecular sieve number 34 (SAPO-34) are developed. Performance results indicate that the synergies between these two components can promote CO2 hydrogenation. Further characterizations reveal that the chabazite (CHA) structure and acid sites in the SAPO-34 are destroyed when preparing In-Zr/SAPO by powder milling (In-Zr/SAPO-M) because of the excessive proximity of two components, which inhibits the activation of CO2 and hydrogen (H2), thus resulting in much higher methane selectivity than the catalysts prepared by granule stacking (In-Zr/SAPO-G). Proper granule integration manner promotes tandem reaction, thus enhancing CO2 hydrogenation to lower olefins, which can provide a practicable strategy to improve catalytic performance and the selectivity of the target products.

Suppression of Methane Formation by Regulating the Hydrogenation Capability of Metal Oxides in Alkylation of Benzene with Syngas

In alkylation of benzene with syngas, the inevitable converting of syngas into methane, as a side reaction, severely hinders the effective utilization of carbon monoxide (CO), which is a major challenge to circumvent. In this work, a series of bifunctional catalysts composed of various zinc/zirconium/cerium metal oxides and HZSM-5 zeolite were prepared in order to explore the key factor of methane formation and achieve high CO efficiency. The results show that methane selectivity mostly depends on the hydrogenation capability, which can be regulated via altering compositions of the metal oxides. Combined with density functional theory calculation and characterizations, it is found that the hydrogenation capability of metal oxide is related to the energy barrier of hydrogen (H2) heterolysis. Compared to CeO2, the addition of zinc favors a lower energy barrier and a stronger ability toward H2 heterolysis, while the addition of zirconium makes this ability weaker. Too strong heterolysis capability consequently leads to excessive hydrogenation, which further causes high methane selectivity; however, too weak heterolysis capability will lead to low catalytic activity. Hence, proper hydrogenation capability is an important element for low methane selectivity and high catalytic activity. Our findings reveal the formation mechanism of methane and provide a new strategy to reduce methane content.

Interfacial Ni active sites strike solid solutional counterpart in CO2 hydrogenation

Ni enhanced CeO2 based catalysts were tested in CO2 hydrogenation reaction with the objective to investigate the importance and role of Ni0 and Ni0-NiO-CeO2−x interfaces. Two materials were prepared: a 4 mol% NiO/CeO2 interfacial oxide where CeO2 supports NiO nanoparticles was produced by wet impregnation method and a Ce0.96Ni0.04O2 mixed oxide was obtained by co-precipitation of Ce3+ and Ni2+ ions. Besides these materials, pure NiO and CeO2 were also synthesized and tested, serving as reference materials. HRTEM, TPR, XRD, BET, EDS, Raman spectroscopy, and XPS were used for the characterization of the catalysts. The activity and selectivity strongly depended on metallic Ni content, which is tunable by the temperature of hydrogen pretreatment. The impregnated catalyst with significant metallic content exhibited high activity and high methane selectivity. The mixed oxide was more resistant to reduction, in the case of both the Ni2+ and Ce4+ species, thus it has low activity with high CO selectivity. The activity and methane selectivity increased considerably by increasing the metal content or higher hydrogen pretreatment temperature. Operando DRIFTS experiments suggested that bicarbonate and formate intermediates play important role in CO2 hydrogenation in both types of catalysts. The reduced Ni particles help to produce the high amount of hydrogen needed for the hydrogenation of formate to methane. It turned out that the metallic Ni not only catalyzes the methane production from formate but also the bicarbonate-formate transformation. The most important factor in the high performance of these catalysts is the Ni0/NiO ratio in the Ni0-NiO-CeO2−x interface.

Monometallic and bimetallic SiC(O) ceramic with Ni, Co and/or Fe nanoparticles for catalytic applications

Monometallic (Ni, Co or Fe-SiC(O)) and bimetallic (Ni, Co or FeM-SiC(O) with M = Ni or Co) ceramic nanocomposites have been successfully prepared using polymeric precursors obtained by chemical modification of polycarbosilane with metal acetylacetonate. The nanocomposites consist of homogeneously distributed metal nanoparticles within an amorphous SiC(O). The specific surface area (SSA) of Ni, Co or Fe-SiC(O)600 nanocomposites were found to be 155, 50 or 14 m2/g. However, the addition of Fe to the Ni-or Co-containing precursors tends to increase the SSA to 290 or 170 m2/g. Maximum CO2 conversion for monometallic samples was found to be 40% at 500 °C for Ni-SiC(O)600 and maximum CH4 selectivity was 61% at 300 °C for Co-SiC(O)600. The additional presence of Co and Ni in the respective nanocomposites helps to increase the CO2 conversion and selectivity at 500 °C whereas Fe modification shows high methane selectivity at lower temperature < 350 °C.

Design of experiments unravels insights into selective ethylene or methane production on evaporated Cu catalysts

As a highly tempting technology to close the carbon cycle, electrochemical CO2 reduction calls for the development of highly efficient and durable electrocatalysts. In the current study, Design of Experiments utilizing the response surface method is exploited to predict the optimal process variables for preparing high-performance Cu catalysts, unraveling that the selectivity towards methane or ethylene can be simply modulated by varying the evaporation parameters, among which the Cu film thickness is the most pivotal factor to determine the product selectivity. The predicted optimal catalyst with a low Cu thickness affords a high methane Faradaic efficiency of 70.6% at the partial current density of 211.8 mA cm−2, whereas that of a high Cu thickness achieves a high ethylene selectivity of 66.8% at 267.2 mA cm−2 in the flow cell. Further structure-performance correlation and in-situ electro-spectroscopic measurements attribute the high methane selectivity to isolated Cu clusters with low packing density and monotonous lattice structure, and the high ethylene efficiency to coalesced Cu nanoparticles with rich grain boundaries and lattice defects. The high Cu packing density and crystallographic diversity is of essence to promoting C–C coupling by stabilizing *CO and suppressing *H coverage on the catalyst surface. This work highlights the implementation of scientific and mathematic methods to uncover optimal catalysts and mechanistic understandings toward selective electrochemical CO2 reduction.

Ga doping disrupts C-C coupling and promotes methane electroproduction on CuAl catalysts

The electrochemical CO 2 reduction reaction (CO 2 RR) provides a route to store intermittent electricity in the form of fuels like methane. We reasoned that disrupting C-C coupling while maintaining high ∗CO coverage could enhance methane selectivity and suppress the hydrogen evolution reaction (HER). We studied the effect of doping CuAl, a material at the top of the CO 2 RR activity and selectivity volcano plot, with elements having low ∗CO binding energies: Au, Zn, and Ga. Encouraged by initial improvements in selectivity to methane, we optimized the Ga content and showed that the presence of uniformly dispersed Ga is crucial in CO 2 RR-to-methane performance enhancement. We rule out porosity and roughness and conclude that the presence of Ga in the doped catalysts enables high methane selectivity. The Ga-doped CuAl catalysts achieve a methane Faradaic efficiency (FE) of 53% by suppressing HER to 23% in neutral electrolyte at −1.4 V versus reversible hydrogen electrode. • Tuning the CO 2 reduction reaction product distribution by disrupting C-C coupling • Porous Ga-doped CuAl catalysts were synthesized • Methane current density of 234 mA/cm 2 and faradaic efficiency of 53% were achieved • Stable operation over 10 h The energy grid needs to shift from fossil fuels to renewable energies, such as wind, solar, nuclear, and hydroelectric energy, in order for society to keep below the 1.5°C global warming threshold. One challenge in achieving this goal is the intermittency of wind and solar electricity. An approach is the electrically powered production of methane, a commodity for which the infrastructure for storage, transportation, and use is well developed. CO 2 RR-to-methane catalysts are in need of improved selectivity, productivity, and stability. Herein, we show how the CO 2 RR product distribution can be redirected from C 2+ products to methane by disrupting carbon-carbon coupling. The material design principles herein contribute to the roadmap for CO 2 RR electrocatalyst design. We shift the CO 2 reduction reaction (CO 2 RR) product distribution from C 2+ products toward methane. Ga doping in CuAl catalysts disrupts carbon-carbon coupling and results in a selectivity shift from ethylene to methane while maintaining low hydrogen evolution activity.

Boosted Inner Surface Charge Transfer in Perovskite Nanodots@Mesoporous Titania Frameworks for Efficient and Selective Photocatalytic CO2 Reduction to Methane.

Exploring high-efficiency and stable halide perovskite-based photocatalysts for the selective reduction of CO2 to methane is a challenge because of the intrinsic photo- and chemical instability of halide perovskites. In this study, halide perovskites (Cs3 Bi2 Br9 and Cs2 AgBiBr6 ) were grown in situ in mesoporous TiO2 frameworks for an efficient CO2 reduction. Benchmarked CH4 production rates of 32.9 and 24.2 μmol g-1 h-1 with selectivities of 88.7 % and 84.2 %, were achieved, respectively, which are better than most reported halide perovskite photocatalysts. Focused ion-beam sliced-imaging techniques were used to directly image the hyperdispersed perovskite nanodots confined in mesopores with tunable sizes ranging from 3.8 to 9.9 nm. In situ X-ray photoelectronic spectroscopy and Kelvin probe force microscopy showed that the built-in electric field between the perovskite nanodots and mesoporous titania channels efficiently promoted photo-induced charge transfer. Density functional theory calculations indicate that the high methane selectivity was attributed to the Bi-adsorption-mediated hydrogenation of *CO to *HCO that dominates CO desorption.

Boosted Inner Surface Charge Transfer in Perovskite Nanodots@Mesoporous Titania Frameworks for Efficient and Selective Photocatalytic CO2 Reduction to Methane

AbstractExploring high‐efficiency and stable halide perovskite‐based photocatalysts for the selective reduction of CO2 to methane is a challenge because of the intrinsic photo‐ and chemical instability of halide perovskites. In this study, halide perovskites (Cs3Bi2Br9 and Cs2AgBiBr6) were grown in situ in mesoporous TiO2 frameworks for an efficient CO2 reduction. Benchmarked CH4 production rates of 32.9 and 24.2 μmol g−1 h−1 with selectivities of 88.7 % and 84.2 %, were achieved, respectively, which are better than most reported halide perovskite photocatalysts. Focused ion‐beam sliced‐imaging techniques were used to directly image the hyperdispersed perovskite nanodots confined in mesopores with tunable sizes ranging from 3.8 to 9.9 nm. In situ X‐ray photoelectronic spectroscopy and Kelvin probe force microscopy showed that the built‐in electric field between the perovskite nanodots and mesoporous titania channels efficiently promoted photo‐induced charge transfer. Density functional theory calculations indicate that the high methane selectivity was attributed to the Bi‐adsorption‐mediated hydrogenation of *CO to *HCO that dominates CO desorption.

CO2 Methanation Over Ni-Sepiolite Catalysts

In this study, it was aimed to develop new catalysts to increase the conversion of environmentally harmful carbon dioxide gas to methane which is a valuable fuel. By using a natural clay mineral sepiolite (SEP) as support material; 6-8% (weight-weight) Ni-containing catalysts were prepared by impregnation. Catalysts were characterized by XRD and FT-IR analysis. Reaction conditions of catalytic hydrogenation of carbon dioxide for methane production were determined as: H2/CO2 = 4 molar ratio, the temperature range of 300-600°C at atmospheric pressure. The output gas mixture was analyzed using the µGC. The activities of the catalysts were determined in terms of carbon dioxide conversion and methane selectivity. 6%Ni/SEP and 8%Ni/SEP provided 65.76% and 68.42% carbon dioxide conversion at 400°C, respectively. In addition, both catalysts exhibited high methane selectivity at 300 and 400°C (>98%).