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Catalytic conversion of CO2 to CO via the reverse water gas shift (RWGS) reaction has been identified as a promising approach for CO2 utilization and mitigation of CO2 emissions. Bare Pt shows low activity for the RWGS reaction due to its low oxophilicity, with few research works having concentrated on the inverse metal oxide/Pt catalyst for the RWGS reaction. In this work, MnOx was deposited on the Pt surface over a SiO2 support to prepare the MnOx/Pt inverse catalyst via a co-impregnation method. Addition of 0.5 wt% Mn to 1 wt% Pt/SiO2 improved the intrinsic reaction rate and turnover frequency at 400 °C by two and twelve times, respectively. Characterizations indicate that MnOx partially encapsulates the surface of the Pt particles and the coverage increases with increasing Mn content, which resembles the concept of strong metal–support interaction (SMSI). Although the surface accessible Pt sites are reduced, new MnOx/Pt interfacial perimeter sites are created, which provide both hydrogenation and C-O activation functionalities synergistically due to the close proximity between Pt and MnOx at the interface, and therefore improve the activity. Moreover, the stability is also significantly improved due to the coverage of Pt by MnOx. This work demonstrates a simple method to tune the oxide/metal interfacial sites of inverse Pt-based catalyst for the RWGS reaction. [ABSTRACT FROM AUTHOR]

A large amount of greenhouse gases, such as carbon dioxide and methane, are released during the production process of bioethanol and biogas. Converting CO2 into methane is a promising way of capturing CO2 and generating high-value gas. At present, CO2 methanation technology is still in the early stage. It requires high temperature (300–400 ℃) and pressure (> 1 MPa), leading to high cost and energy consumption. In this study, a new catalyst, Ni–Fe/Al–Ti, was developed. Compared with the activity of the common Ni/Al2O3 catalyst, that of the new catalyst was increased by 1/3, and its activation temperature was reduced by 100℃. The selectivity of methane was increased to 99%. In the experiment using simulated fermentation gas, the catalyst showed good catalytic activity and durability at a low temperature and atmospheric pressure. Based on the characterization of catalysts and the study of reaction mechanisms, this article innovatively proposed a Ni–Fe/Al–Ti quaternary catalytic system. Catalytic process was realized through the synergism of Al–Ti composite support and Ni–Fe promotion. The oxygen vacancies on the surface of the composite carrier and the higher activity metals and alloys promoted by Fe accelerate the capture and reduction of CO2. Compared with the existing catalysts, the new Ni–Fe/Al–Ti catalyst can significantly improve the methanation efficiency and has great practical application potential. [ABSTRACT FROM AUTHOR]

The reverse water-gas shift (RWGS) reaction is one of the effective ways of carbon dioxide (CO2) conversion. However, the RWGS catalyst has the problem of poor stability under high temperature. A series of Co/SiO2 catalysts with promoters (CeO2, La2O3, Y2O3 or ZrO2) were prepared by incipient-wetness impregnation method for the RWGS reaction. The catalysts were characterized by X-ray diffractometry, transmission electron microscopy and H2-programmed temperature reduction, etc. The effects of promoters on the catalyst structure and RWGS reaction performance were studied. The results of catalyst characterization show that the particle size of Co3O4 in the catalyst is not significantly changed by adding promoters. The promoters of CeO2, La2O3, Y2O3 and ZrO2 interacte with the cobalt component. The catalytic performance test results show that the CO2 conversion rate of the Co/SiO2 catalysts decreases from 28.3% to 9.0% after reaction at 600 °C for 12 h. The stability of the catalysts with promoters is improved, and the Co-ZrO2/SiO2 catalyst has the best stability, and the CO2 conversion rate is still as high as 21.9% after reaction for 12 h. This is due to the presence of interaction between the promoters and the cobalt component after the addition of the promoters, which improves the stability of the active component of cobalt. [ABSTRACT FROM AUTHOR]

The fundamental insights of the reaction mechanism, especially the synergistic effect between oxygen vacancies and basic sites, are highly promising yet challenging for Ru-based catalysts during carbon dioxide (CO2) methanation. Herein, a series of Ru-based catalysts were employed to study the mechanism of CO2 methanation. It is found that Ru/CeO2 catalyst exhibits a much higher CO2 conversion (86%) and CH4 selectivity (100%), as well as excellent stability of 30 h due to the existence of abundant oxygen vacancies and weak basic sites. Additionally, the in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and density functional theory (DFT) calculations reveal that the formate formation step dominated the hydrogenation route on Ru/CeO2 catalyst, and the b-HCOO* could be the key intermediate due to b-HCOO* is more easily hydrogenated to methane than m-HCOO*. The systematic study marks the significance of precise tailoring of the synergistic relationship between oxygen vacancies and basic sites for achieving the desired performance in CO2 methanation. [ABSTRACT FROM AUTHOR]

Atomically dispersed Ir confined in amorphous MoO3 (Ir1/a-MoO3) was designed as a high-efficiency catalyst for electrochemical reduction reaction of NO to NH3 (NORR). Atomic precise characterizations reveal that isolated Ir atoms are immobilized in O-vacancies of amorphous MoO3 to form Ir1-O5 moieties. Theoretical computations demonstrate that single-site Ir1-O5 can not only powerfully activate and hydrogenate NO with a near-zero energy barrier, but also exhibit a higher affinity to NO over H adatoms to suppress the competing hydrogen evolution and promote both NORR activity and selectivity. Consequently, Ir1/a-MoO3 shows the maximum NH3 yield rate of 438.8 µmol·h−1·cm−2 and NH3-Faradaic efficiency of 93.2%, representing one of the most efficient NORR catalysts to date. [ABSTRACT FROM AUTHOR]

Herein, we explore how OH groups on Pt/γ‐AlOOH and Pt/γ‐Al2O3 catalysts affect CO2 hydrogenation with H2 at temperatures from 250°C to 400°C. OH groups are abundant on γ‐AlOOH, but rare at Pt‐(γ‐AlOOH) interface which is the most favorable site for CO2 conversion on Pt/γ‐AlOOH. This makes CO2 hydrogenation on Pt/γ‐AlOOH form CO weakly bonding to γ‐AlOOH, which prefers to desorption from Pt/γ‐AlOOH rather than further conversion, thus enhancing CO production on Pt/γ‐AlOOH. Different from Pt/γ‐AlOOH, OH groups are abundant at Pt‐(γ‐Al2O3) interface which is the most favorable site for CO2 conversion on Pt/γ‐Al2O3. This promotes CO2 hydrogenation on Pt/γ‐Al2O3 to form CO strongly bonding to Pt, which prefers to further hydrogenation to CH4, and thereby increases CH4 selectivity on Pt/γ‐Al2O3. Therefore, the OH groups at metal‐support interface are crucial factor influencing product distribution, and must be considered seriously when fabricating catalysts. [ABSTRACT FROM AUTHOR]

Formic acid has recently been revealed to be an excellent hydrogen carrier, and interest in the development of efficient and selective catalysts towards its dehydrogenation has grown. This reaction has been widely explored using homogeneous catalysts; however, from a practical and scalable point of view, heterogeneous catalysts are usually preferred in industry. In this work, formic acid dehydrogenation reactions in both liquid- and vapor-phase conditions have been investigated using heterogeneous catalysts based on mono- or bimetallic Pd/Ru. In all of the explored conditions, the catalysts showed good catalytic activity and selectivity towards the dehydrogenation reaction, avoiding the formation of undesired CO. [ABSTRACT FROM AUTHOR]

In this work, the effect of ethanol co-feeding in the synthesis of higher alcohols from syngas over K-MoS2 catalyst was investigated in a batch reactor, and the yield of higher alcohols was improved. K-MoS2 prepared with thiourea as a sulfur source exhibited better performance for synthesizing higher alcohols from syngas due to its more stacking layers, higher specific surface area and more Mo4+ active species. Ethanol co-feeding could provide more alkyl intermediate species, which was conducive to the insertion of CO, thereby promoting the conversion of CO and the production of higher alcohols. A change in the reaction path from insertion of CO to homocoupling of ethanol was found upon increasing the ethanol to CO ratio. Higher alcohols production was maximized with the side products in an acceptable range for n EtOH/n CO = 0.3. [ABSTRACT FROM AUTHOR]

Integrated CO2 capture and hydrogenation to produce formate offers a sustainable approach for reducing carbon dioxide emissions and producing liquid hydrogen carriers (formate) simultaneously. In the current study, three different types of aqueous amine solutions including monoethanolamine (MEA), diethanolamine (DEA) and triethanolamine (TEA) were investigated as CO2-capturing and hydrogenation agents in the presence of a Pd/NAC catalyst. The effect of amine structures on the CO2 absorption products and formate yield was investigated thoroughly. It was found that the formate product was successfully produced in the presence of all three aqueous amine solutions, with tertiary amine TEA accounting for the highest formate yield under the same CO2 loadings. This is due to the fact that primary and secondary amine moieties in MEA and DEA are responsible for the formation of CO2 adducts of carbamate and bicarbonate, whereas the tertiary amine moiety in TEA is responsible for the formation of hydrogenation-favorable bicarbonate as the solo CO2 absorption product. A high yield of formate of 82.6% was achieved when hydrogenating 3 M TEA with 0.3 mol CO2/mol amine solution in the presence of a Pd/NAC catalyst. In addition, the physio-chemical properties of the Pd/NAC catalyst analyzed using TEM, XRD and XPS characterization were applied to rationalize the superior catalytic performance of the catalyst. The reaction mechanism of integrated CO2 capture and hydrogenation to produce formate in aqueous amine solutions over Pd/NAC catalyst was proposed as well. [ABSTRACT FROM AUTHOR]

An Ni-CeO2 catalyst with high Ni loading (50 wt.%) prepared by a salt-assisted solution combustion method was characterized by different methods and used for CO2 methanation. The specific surface area of the Ni-CeO2 catalyst prepared by salt-assisted solution combustion is 7 times that of the catalyst prepared by conventional solution combustion. The Ni-CeO2 catalyst prepared by salt-assisted solution combustion has smaller particle sizes of Ni and exhibits excellent activity at low temperatures. The high Ni loading and small Ni particle size can provide more metal Ni site and Ni-CeO2 interface, which help to improve the CO2 methanation performance. [ABSTRACT FROM AUTHOR]

Propane dehydrogenation has been a promising method for producing propylene that has the potentials to meet the increasing global demand for propylene. However, owing to the restricted equilibrium conversion caused by the high endothermicity, even the Pt‐based catalysts, which exhibit high activity and selectivity, severely suffer significantly from coke formation and/or nanoparticle sintering at realistic reaction temperatures, resulting in a short catalyst lifetime. As a result, few innovative catalysts in terms of catalytic activity, selectivity, and stability, have been produced. In this Review, we focus on the characteristics of single‐atom‐like Pt sites for PDH and attempt to provide suggestions for developing highly efficient catalysts. First, we briefly describe the fundamental strategies. Following that, the remarkable catalysis is addressed by three different distinct sorts of state‐of‐the‐art single‐atom‐like Pt catalysts are discussed. Additionally, we present other promising catalyst design approaches that are not based on single‐atom‐like Pt catalysts, as well as future research challenges in this field. [ABSTRACT FROM AUTHOR]

La1−xSrxCoO3 (x=0, 0.1, 0.2, 0.3, 0.4) nanoparticles were prepared by spray‐flame synthesis and applied in the liquid‐phase oxidation of cyclohexene with molecular O2 as oxidant under mild conditions. The catalysts were systematically characterized by state‐of‐the‐art techniques. With increasing Sr content, the concentration of surface oxygen vacancy defects increases, which is beneficial for cyclohexene oxidation, but the surface concentration of less active Co2+ was also increased. However, Co2+ cations have a superior activity towards peroxide decomposition, which also plays an important role in cyclohexene oxidation. A Sr doping of 20 at. % was found to be the optimum in terms of activity and product selectivity. The catalyst also showed excellent reusability over three catalytic runs; this can be attributed to its highly stable particle size and morphology. Kinetic investigations revealed first‐order reaction kinetics for temperatures between 60 and 100 °C and an apparent activation energy of 68 kJ mol−1 for cyclohexene oxidation. Moreover, the reaction was not affected by the applied O2 pressure in the range from 10 to 20 bar. In situ attenuated total reflection infrared spectroscopy was used to monitor the conversion of cyclohexene and the formation of reaction products including the key intermediate cyclohex‐2‐ene‐1‐hydroperoxide; spin trap electron paramagnetic resonance spectroscopy provided strong evidence for a radical reaction pathway by identifying the cyclohexenyl alkoxyl radical. [ABSTRACT FROM AUTHOR]

The research work conducted mainly on the reduction reaction of NOx, the oxidation reaction of CO, and hydrocarbons, electro‐catalysis of oxygen in alkaline medium, and photocatalytic water splitting has proved excellent catalytic behavior of perovskite oxides.[16–23] Although only a few reports published usages of the perovskite oxides as catalysts for the organic transformation such as catalytic hydrogenation, Ullmann, Sonogashira reactions, and Suzuki couplings.[24–26] Yoon et al. have prepared K2CO3 based LaMn1‐xCuxO3 perovskite oxide as a potential catalyst and discussed their mechanistic aspects in various reactions occurring at room temperature.[27] Recently, Wu and Ajayan group has demonstrated the relationship between stoichiometry and activity of pure and B‐site substituted layered perovskite oxide in the decomposition reaction of isopropanol by considering Sr2Sn1‐xRuxO4 (0≤x≤1) as catalyst.[28] In this scenario, present work aims to summarize the contribution of perovskite oxides as catalyst in numerous organic syntheses and catalysis, photocatalysis, and electrocatalysis reactions. [ABSTRACT FROM AUTHOR]

Zn- and Mn-doped Cerium-oxide based catalyst textured as a solid solutional as well as interfacial form was compared in CO2 hydrogenation reaction to understand the role of texture as well as dopant type. Ce0.9M0.1O2 (M = Zn, Mn) solid solution was prepared by hydrothermal method and CeO2 supported 10 mol% metal oxide (Metal = Zn, Mn) were prepared by wet impregnation method, where the catalysts were characterized by XRD, N2 adsorption/desorption isotherm, TEM, Raman spectra, HAADF-STEM and H2-TPR. During the CO2 activation reaction, CO was the major product with minor amounts of methane, ethane, methanol and ethanol. In the case of the Zn-doped CeO2 catalyst, the presence of Zn improved catalytic activity in both solid solutional and interfacial form due to the synergetic effect of Zn-Ce-based oxide. However, for MnOx/CeO2 catalysts, the CO2 consumption rate significantly decreased for 10 mol% MnOx/CeO2, Ce0.9Mn0.1O2 and Mn3O4, where the MnOx addition inhibits the reduction of CeO2. In the case of the pure CeO2, DRIFTS spectra show that formate intermediate formed by reaction between activated CO2 and OH transformed into methoxy species through formaldehyde intermediates, which leads to the formation of small amount of methanol and ethanol. [ABSTRACT FROM AUTHOR]

Sulfate radical-based advanced oxidation technologies (SR-AOTs) are very effective solutions to remove organic pollutants from wastewater. Nevertheless, difficulties remain in finding an efficient and environmentally friendly catalytic system to activate peroxymonosulfate (PMS) for the oxidation process. In this work, a simple impregnation method for synthesizing layered Co(OH)2 deposited g-C3N4 (Co(OH)2/g-C3N4) was developed. The as-obtained Co(OH)2/g-C3N4 showed excellent performance in the destruction of various organic pollutants through PMS activation. The structure, morphology and composition of Co(OH)2/g-C3N4 were analyzed using diverse characterization methods. Various experimental parameters such as catalyst loading, initial PMS concentration, pH, reaction temperature and initial organic pollutant concentration were studied in detail. The obtained Co(OH)2/g-C3N4 composite can completely degrade Rhodamine B (RhB) with a high reaction rate constant of 0.460 min−1 under the optimal conditions, which was much higher than those of Co(OH)2, g-C3N4 and many other metal catalysts. This was because the synergistic effect between the layered Co(OH)2 with sufficient active sites and electron-rich g-C3N4 with good electron transfer ability can accelerate the activation of PMS. Besides, radical quenching experiments indicated that sulfate radicals (SO4˙−) were the major active radicals in the PMS activation process. Finally, the degradation pathways and a reasonable reaction mechanism of the Co(OH)2/g-C3N4/PMS system for RhB removal were put forward. The study revealed that Co(OH)2/g-C3N4 could provide appropriate strategies for the removal of organic pollutants in aqueous environments. [ABSTRACT FROM AUTHOR]

Global greenhouse effect is being exacerbated by continuously increasing CO2 emissions. Hence, we prepared a nanoscale zero‐valent Ni–Fe alloy featuring a dual galvanic effect to facilitate the formation of formate by CO2 hydrogenation in this work. The properties of the bimetallic nanocatalyst were characterized by various techniques, such as X‐ray photoelectron spectrometer, X‐ray powder diffraction, and high‐resolution transmission electron microscopy, indicating that the major phase composition was an alloy of Ni0 and Fe0. According to the catalyst characterizations before and after the reaction, experimental phenomena, and related literatures, we proposed that the dual galvanic effect between Ni0 and Fe0 was an especially important mechanism to promote the release of BH4‐n(OH)n– (n = 0–3) from KBH4, which acted as the hydrogen donor for CO2. Furthermore, the optimization of process parameters was carried out to determine the optimal experimental conditions: the catalyst dosage was 1 g·L–1, the KBH4 concentration was 0.2 mol·L–1, the reaction temperature was 65 °C, the solution pH was 9.5 and the flue gas velocity was 0.5 L·min–1. The average CO2 conversion efficiency and the formate selectivity reached 60.50 and 54.97%, respectively. Our research results can provide reference for the development of novel CO2 resource utilization technologies. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Meeting the escalating demand for clean water resources is one of the key challenges to ensure a sustainable future. Catalysis plays an important role to advance the chemical reactions required for wastewater efficient remediation. How to exploit high‐performance catalysts to boost the pivotal reaction kinetics always attracts researchers' enthusiasm. Perovskite oxides as a novel class of functional materials can be tuned to confer compositional flexibilities and provide rich and unique structural properties. As the rising‐star material, it has been widely probed for electrocatalysis, photocatalysis, and membrane‐catalysis for energy conversion, but received less attention in water treatment. In this review, the advances of perovskite oxides for advanced oxidation processes (AOPs) in water remediation are comprehensively elaborated. A fundamental understanding of the crystal structures and properties of perovskite oxides as well as the basic principles of AOPs is firstly provided. Then, emphasis is placed on how to tune the perovskite oxides to suit various AOPs. The strategies to design novel perovskite oxides to enhance the catalytic activities in AOPs have been highlighted. It is expected that after reading this review, readers will have a clearer vision of the background, the state of the art development, and general guidelines for future directions regarding research in this area. [ABSTRACT FROM AUTHOR]

Summary: Methanation is an exothermic process that utilizes catalysts to convert the carbon dioxide and carbon monoxide in biogas to methane, forming synthetic natural gas. The criteria for determining a suitable catalyst should not only be its effectiveness, but also the environmental impact of extracting and refining the metal. The authors examine the environmental impacts of implementing a select group of methanation catalysts in the field for industrial scale synthetic natural gas production using the analytical hierarchy process (AHP). Catalysts containing a combination of rare earth metals are investigated separately and AHP is used to rank the catalysts based on their environmental impact per kg of CO2 converted. It is determined that catalysts containing common metals, such as nickel, have the lowest environmental impact per conversion rate across a number of metrics and represented the catalysts with the second and third highest conversion rates analyzed. Catalysts containing ruthenium are found to be the most detrimental to the environment, in spite of the favorable conversion rate offered by a ruthenium‐cesium catalyst in methanation reactors. [ABSTRACT FROM AUTHOR]

Au@Pd core-shell nanobricks (CNBs) with concave surfaces and Pd shells with a thickness of approximately 5 nm were synthesized by co-reduction of HAuCl4 and H2PdCl4 in the presence of Au seeds and Ag ions. These as-synthesized concave CNBs exhibit significantly enhanced catalytic activity for the electrooxidation of ethanol in alkaline media compared to the commercially-used Pd black. The improved performance of the Au@Pd CNBs can be attributed to the exposed stepped surfaces, high-index facets, and the synergistic effects of the core and shell metals. [ABSTRACT FROM AUTHOR]

Metallic Pt sites are imperative in the CO oxidation reaction. Herein, we demonstrate the tuning of Pt sites by treating a Pt catalyst in various reductive atmospheres, influencing the catalyst activities in low-temperature CO oxidation. The H2 pretreatment of Pt clusters at 200 °C decreases the T50 from 208 °C to 183 °C in the 0.1 wt % Pt/TiO2 catalyst. The T50 shows a remarkable improvement using a CO pretreatment, which decreases the T50 further to 135 °C. A comprehensive characterization study reveals the integrated reasons behind this phenomenon: (i) the extent of PtO transition to metallic Pt sites, (ii) the ample surface active oxygen triggered by metallic Pt, (iii) the CO selectively adsorbs on metallic Pt sites which participate in low-temperature CO oxidation, and (iv) the formation of the unstable intermediate such as bicarbonate, contributes together to the enhanced activity of CO pretreated Pt/TiO2. [ABSTRACT FROM AUTHOR]

Copper catalysts were widely developed for CO2 conversion, but suffered severe sintering at temperatures higher than 300 °C. Platinum was the most active and stable metal for RWGS reactions. However, the high price and scarcity of platinum restrained its application. Downsizing the metal particles can significantly improve the atom efficiency of the precious metal but the size effect of Pt on RWGS reactions was still unclear. In the present work, the single atomic Pt on SrTiO3 was prepared using an impregnation leaching method, and the catalyst showed significant activity for an RWGS reaction, achieving a CO2 conversion rate of 45%, a CO selectivity of 100% and a TOF of 0.643 s−1 at 500 °C. The structures of the catalysts were characterized using XRD, STEM and EXAFS. Especially, the size effect of Pt in RWGS was researched using in situ FTIR and DFT calculations. The results reveal that single Pt atoms are the most active species in RWGS via a "–COOH route" while larger Pt cluster and nanoparticles facilitate the further hydrogenation of CO. The reaction between formate and H* is the rate determination step of an RWGS reaction on a catalyst, in which the reaction barrier can be lowered from 1.54 eV on Pt clusters to 1.29 eV on a single atomic Pt. [ABSTRACT FROM AUTHOR]

A series of Ni-xSi/ZrO2 (x = 0, 0.1, 0.5, 1 wt%, the controlled contents of Si) catalysts with a controlled nickel content of 10 wt% were prepared by the co-impregnation method with ZrO2 as support and Si as a promoter. The effect of different amounts of Si on the catalytic performance was investigated for CO2 methanation with the stoichiometric H2/CO2 molar ratio (4/1). The catalysts were characterized by BET, XRF, H2-TPR, H2-TPD, H2-chemisorption, CO2-TPD, XRD, TEM, XPS, and TG-DSC. It was found that adding the appropriate amount of Si could improve the catalytic performance of Ni/ZrO2 catalyst at a low reaction temperature (250 °C). Among all the catalysts studied, the Ni-0.1Si/ZrO2 catalyst showed the highest catalytic activity, with H2 and CO2 conversion of 73.4% and 72.5%, respectively and the yield of CH4 was 72.2%. Meanwhile, the catalyst showed high stability and no deactivation within a 10 h test. Adding the appropriate amount of Si could enhance the interaction between Ni and ZrO2, and increase the Ni dispersion, the amounts of active sites including surface Ni0, oxygen vacancies, and strong basic sites on the catalyst surface. These might be the reasons for the high activity and selectivity of the Ni-0.1Si/ZrO2 catalyst. [ABSTRACT FROM AUTHOR]

CO2 hydrogenation toward methane, a reaction of high environmental and sustainable energy importance, was investigated at 200–600 °C and H2/CO2 = 4/1, over Rh nanoparticles dispersed on supports with different oxygen storage capacity characteristics (γ-Al2O3, alumina-ceria-zirconia, and ceria-zirconia). The effects of the support OSC and Rh particle size on reaction behavior under both integral and differential conditions were investigated, to elucidate the combined role of these crucial catalyst design parameters on methanation efficiency. A volcano-type variation of methanation turnover frequency was found in respect to support OSC; Rh/ACZ, with intermediate OSC, was the optimal catalyst. The structure sensitivity of the reaction was found to be a combined function of support OSC and Rh particle size: For Rh/γ-Al2O3 (lack of OSC) methanation was strongly favored on small particles—the opposite for Rh/CZ (high OSC). The findings are promising for rational design and optimization of CO2 methanation catalysts by tailoring the aforementioned characteristics. [ABSTRACT FROM AUTHOR]

Mesoporous Ni-based catalysts with Ni confined in nanochannels are widely used in CO2 methanation. However, when Ni loadings are high, the nanochannels are easily blocked by nickel particles, which reduces the catalytic performance. In this work, three-dimensional mesoporous Ni-CeO2-CSC catalysts with high Ni loadings (20−80 wt %) were prepared using a colloidal solution combustion method, and characterized by nitrogen adsorption–desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM) and H2 temperature programmed reduction (H2-TPR). Among the catalysts with different Ni loadings, the 50% Ni-CeO2-CSC with 50 wt % Ni loading exhibited the best catalytic performance in CO2 methanation. Furthermore, the 50% Ni-CeO2-CSC catalyst was stable for 50 h at 300° and 350 °C in CO2 methanation. The characterization results illustrate that the 50% Ni-CeO2-CSC catalyst has Ni particles smaller than 5 nm embedded in the pore walls, and the Ni particles interact with CeO2. On the contrary, the 50% Ni-CeO2-CP catalyst, prepared using the traditional coprecipitation method, is less active and selective for CO2 methanation due to the larger size of the Ni and CeO2 particles. The special three-dimensional mesoporous embedded structure in the 50% Ni-CeO2-CSC can provide more metal–oxide interface and stabilize small Ni particles in pore walls, which makes the catalyst more active and stable in CO2 methanation. [ABSTRACT FROM AUTHOR]

Ni-Ce-Zr-Oδ catalysts were prepared via one-pot hydrothermal synthesis. It was found that Ni can be partially incorporated into the Ce-Zr lattice, increasing surface oxygen species. The catalysts possess high surface areas even at high Ni loadings. The catalyst with Ni content of 71.5 wt.% is able to activate CO2 methanation even at a low temperature (200 °C). Its CO2 conversion and methane selectivity were reported at 80% and 100%, respectively. The catalyst was stable for 48 h during the course of CO2 methanation at 300 °C. Catalysts with the addition of medium basic sites were found to have better catalytic activity for CO2 methanation. [ABSTRACT FROM AUTHOR]

The resistance to sintering of Ni/Al2O3 catalysts with different additives for methanation reaction was modeled and predicted by data mining. In the screening, the resistance to sintering of Na, Ca, Ce, Mg, La, Cu, Zn, Zr, In, Mo, and Ti promoted Ni/Al2O3 catalyst were measured in terms of the increased rate of the size of the metallic nickel particles. The resistance to sintering of catalysts, described by the increased rate of Ni particle size as well as basic physicochemical properties of the 11 selected elements, was adopted for optimization model construction by data mining. Through regression model prediction and experimental verification, Cs was found to be an additive, and promotes the resistance to sintering mostly for Ni/Al2O3 catalysts. This result provides further evidence that data mining techniques can be employed as a highly efficient tool for the discovery of new catalysts in comparison with the traditional experimental method. [ABSTRACT FROM AUTHOR]

In this work, we present an investigation concerning the evaluation of the catalytic properties of Ni nanoparticles supported on ZrO2, SiO2, and MgAl2O4 for CO2 hydrogenation to methane. The supports were prepared by coprecipitation and sol-gel, while Ni was incorporated by impregnation (10–20 wt %). X-ray diffraction, nitrogen physisorption, temperature-programmed reduction, H2 pulse chemisorption, Raman spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy were the main characterization techniques employed. A laboratory fixed-bed reactor operated at atmospheric pressure, a temperature range of 350–500 °C, and a stoichiometric H2/CO2 molar ratio was used for catalyst evaluation. The most outstanding results were obtained with nickel catalysts supported on ZrO2 with CO2 conversions of close to 60%, and selectivity to methane formation was 100% on a dry basis, with high stability after 250 h of reaction time. The majority presence of tetragonal zirconia, as well as the strong Ni–ZrO2 interaction, were responsible for the high catalytic performance of the Ni/ZrO2 catalysts. [ABSTRACT FROM AUTHOR]

Cost‐effective, stable, and highly efficient heterogeneous catalyst is the key challenge for wastewater treatment based on Fenton‐like advanced oxidation processes. Perovskite oxides offer new opportunities because of their versatile compositions and flexible physiochemical properties. Herein, a new strategy is proposed that is different from the frequently used alien‐metal doping, to tune surface properties of perovskite oxides by nanocompositing perovskite with inert oxide, resulting in improved activity and stability for catalytic oxidation. By in situ modification of LaFeO3 with inert La2O3 oxide through one‐pot synthesis, several important surface properties such as surface defects, H2O2 adsorption capacity, Fe2+ concentration, and charge‐transfer rate were improved, as well as resistance against iron leaching. In performance evaluation, among the various materials, La1.15FeO3 (L1.15FO) composite shows the highest Fenton activity (0.0402 min−1) for activating H2O2 to oxidize methyl orange, 2.5 times that of the pristine LaFeO3. Notably, in situ electron paramagnetic resonance analysis and radical scavenging tests unveil a faster generation of singlet oxygen as the dominant reactive species over L1.15FO, consequently a novel non‐radical activation mechanism is proposed. Such improved performance is assigned to the strong coupling effect between the nanosized LaFeO3 and La2O3 in the hybrids, which fine‐tune the surface properties of LaFeO3 perovskite as superior Fenton catalysts. Fine‐tuning surface properties and structure of perovskites via nanocompositing with inert oxide toward developing superior catalysts for advanced oxidation. [ABSTRACT FROM AUTHOR]