The synergistic interaction among different components in complex catalysts is one of the crucial factors in determining catalytic performance. Here we report the interactions among the three components in controlling the catalytic performance of Cu–ZnO–ZrO2 (CZZ) catalyst for CO2 hydrogenation to methanol. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements under the activity test pressure (3 MPa) reveal that the CO2 hydrogenation to methanol on the CZZ catalysts follows the formate pathway. Density functional theory (DFT) calculations agree with the in situ DRIFTS measurements, showing that the ZnO–ZrO2 interfaces are the active sites for CO2 adsorption and conversion, while the presence of metallic Cu is also necessary to facilitate H2 dissociation and to provide hydrogen resource. The combined experiment and DFT results reveal that tuning the interaction between ZnO and ZrO2 can be considered as another important factor for designing high performance catalysts for methanol generation from CO2.

Catalytic hydrogenation of CO 2 with renewable H 2 to methanol represents a promising pathway for reducing anthropogenic CO 2 emissions. Catalysts play a key role in enhancing both the hydrogenation rate and methanol selectivity. ZrO 2 is a promising catalyst support, promoter and even active species for CO 2 hydrogenation due to its versatile properties and weak hydrophilic character. Over the past decades substantial progress has been made in designing high performance catalysts and understanding the hydrogenation mechanisms over ZrO 2 -supported catalysts. ZrO 2 interacts with metals and/or other oxides and consequently may affect the CO 2 adsorption and activation, enhance the dissociation of H 2 and spillover of atomic hydrogen, change the reaction pathways and/or the binding of key reaction intermediates for further conversion. The synergistic effects induced by ZrO 2 could be achieved by improving the metal dispersion, modifying surface basicity and interacting with other components (metals, cosupports or promoters). However, although experimental and computational investigations have been extensively performed, the multiple roles of ZrO 2 in the catalytic process are still under debate. In the current Perspective, we use ZrO 2containing catalysts as a model system to elucidate the governing principles for designing high performance catalysts with multiple active components for CO 2 hydrogenation to methanol.

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With highly tunable composition, structure, and chemical-physical properties, perovskite oxides represent a large family of mixed-oxide materials that finds many energyand environment-related applications. This perspective discusses the fundamentals and applications of perovskite oxides in the context of chemical looping and three-way catalysis (TWC). Both applications make use of perovskite oxides' oxygen storage and donation properties (>400 μmol O/g) under macroscopic reduction−oxidation (redox) cycles and at elevated temperatures. While perovskite oxides have been investigated as oxygen storage materials (OSMs) and three-way catalysts for more than five decades, use of these oxides in chemical looping, as oxygen carriers or redox catalysts, is a relatively new topic. This article provides an account of the effects of compositional, structural, and surface properties of perovskites on their oxygen storage and donation properties as well as their interactions with various gaseous reactants. Design and optimization strategies of tailored perovskite OSMs for chemical looping and TWC are discussed. Emerging applications of perovskite-based redox catalysts for chemical looping partial oxidation are also covered.

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Chemical-looping steam methane reforming (CL-SMR) is a promising method for the co-generation of pure hydrogen and syngas on the basis of redox cycles via a gas−solid reaction using an oxygen carrier. The performance and life of the oxygen carrier play pivotal roles in determining the feasibility and economy of the CL-SMR process. The present research was focused on the evolution of the structure and reducibility of a CeO 2 −Fe 2 O 3 oxygen carrier during the CL-SMR redox process to further understand the sustainability of the oxygen carrier. The investigated CeO 2 −Fe 2 O 3 complex oxide exhibited satisfactory performance in the CL-SMR process because of the chemical interaction between Ce and Fe species. A Ce−Fe−O phase equilibrium based on a stable composition of CeO 2 , Fe 3 O 4 , and CeFeO 3 formed in the recycled samples. Surface oxygen was removed, which was accompanied by an increase in the concentration of oxygen vacancies and a decrease in the surface area of the recycled samples; these effects resulted in an increase in the high-temperature reducibility and syngas selectivity of the samples. Oxygen mobility was intensified by the Ce−Fe chemical interaction via the formation of CeFeO 3 and a micromorphological transformation. These properties counteracted the sintering of the materials and guaranteed the stability of the oxygen carrier in the CL-SMR process.

Hydrogenation of CO 2 is attractive to reduce CO 2 emissions and produce valueadded chemicals (e.g., methanol) with renewable energy. However, the mechanistic understanding of the role of water, a byproduct of CO 2 conversion to methanol, is still missing. Here, we identify that water directly participates in methanol formation via methoxy hydrolysis, and the enhancement on the water vapor diffusion strongly improves methanol selectivity and yield.

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