Influence of Ag Metal Dispersion on the Catalyzed Reduction of CO₂ into Chemical Fuels over Ag–ZrO₂ Catalysts

Metal/metal oxide catalysts reveal unique CO2 adsorption and hydrogenation properties in CO2 electroreduction for the synthesis of chemical fuels. The dispersion of active components on the surface of metal oxide has unique quantum effects, significantly affecting the catalytic activity and selectivity. Catalyst models with 25, 50, and 75% Ag covering on ZrO2, denoted as Ag4/(ZrO2)9, Ag8/(ZrO2)9, and Ag12/(ZrO2)9, respectively, were developed and coupled with a detailed investigation of the electronic properties and electroreduction processes from CO2 into different chemical fuels using density functional theory calculations. The dispersion of Ag can obviously tune the hybridization between the active site of the catalyst and the O atom of the intermediate species CH3O* derived from the reduction of CO2, which can be expected as the key intermediate to lead the reduction path to differentiation of generation of CH4 and CH3OH. The weak hybridization between CH3O* and Ag4/(ZrO2)9 and Ag12/(ZrO2)9 favors the further reduction of CH3O* into CH3OH. In stark contrast, the strong hybridization between CH3O* and Ag8/(ZrO2)9 promotes the dissociation of the C–O bond of CH3O*, thus leading to the generation of CH4. Results provide a fundamental understanding of the CO2 reduction mechanism on the metal/metal oxide surface, favoring novel catalyst rational design and chemical fuel production

Effects of *CO Coverage on Selective Electrocatalytic Reduction of CO₂ to Ethylene over Cu₂O with Undercoordinated Cu Sites

Cu2O surface with the coordinatively unsaturated Cu sites reveals advantages in the electroreduction of CO2 toward C2H4 production. Understanding the role of *CO coverage and veritable active sites is of great significance for a good command of the catalytic mechanism. Herein, based on density functional theory, the effects of *CO coverage during the reduction of CO2 to C2H4 on various active sites of Cu2O(111) surface, in terms of the adsorption and structural changes of *CO and key intermediates; the energy profiles of the C–C coupling steps; and the subsequent reaction mechanisms were investigated. Results show that CuCUS on the Cu2O(111) surface is especially reactive toward the *CO adsorption and subsequent reactions, being the preferred site owing to the unsaturated Cu atoms. The *CO coverage obviously tunes the adsorption stability of *COH and *CHO intermediates by affecting the adsorbent–adsorbent interactions. Higher coverage of *CO within 0.13–0.25 promotes the C–C coupling by lowering the energy barrier of *CH2 dimerization, favoring the C2H4 production. Due to the more facile generation of *CHO than *COH, the rate-determining step is speculated to be the C–C coupling with the highest barrier energy occurring in the *CHO pathway. Results provide a fundamental understanding of the CO2 reduction mechanism on Cu-based surfaces, favoring novel catalysts, rational design, and chemical fuel production