Cu 2 O surface with the coordinatively unsaturated Cu sites reveals advantages in the electroreduction of CO 2 toward C 2 H 4 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 CO 2 to C 2 H 4 on various active sites of Cu 2 O(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 Cu CUS on the Cu 2 O(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 *CH 2 dimerization, favoring the C 2 H 4 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 CO 2 reduction mechanism on Cu-based surfaces, favoring novel catalysts, rational design, and chemical fuel production.
Metal/metal oxide catalysts reveal unique CO 2 adsorption and hydrogenation properties in CO 2 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 ZrO 2 , denoted as Ag 4 /(ZrO 2 ) 9 , Ag 8 /(ZrO 2 ) 9 , and Ag 12 /(ZrO 2 ) 9 , respectively, were developed and coupled with a detailed investigation of the electronic properties and electroreduction processes from CO 2 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 CH 3 O * derived from the reduction of CO 2 , which can be expected as the key intermediate to lead the reduction path to differentiation of generation of CH 4 and CH 3 OH. The weak hybridization between CH 3 O * and Ag 4 /(ZrO 2 ) 9 and Ag 12 /(ZrO 2 ) 9 favors the further reduction of CH 3 O * into CH 3 OH. In stark contrast, the strong hybridization between CH 3 O * and Ag 8 /(ZrO 2 ) 9 promotes the dissociation of the C–O bond of CH 3 O * , thus leading to the generation of CH 4 . Results provide a fundamental understanding of the CO 2 reduction mechanism on the metal/metal oxide surface, favoring novel catalyst rational design and chemical fuel production.
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