Efficacious CO Adsorption and Activation on Ag Nanoparticles/CuO Mesoporous Nanosheets Heterostructure for CO Electroreduction to CO.

It is an ongoing pursuit for researchers to precisely control the catalyst's surface for high-performance CO electrochemical reduction (COER). In this work, CuO mesoporous nanosheets (CuO MNSs) with rough edges decorated by small Ag nanoparticles (Ag NPs) with a tunable amount of Ag were synthesized on a Cu foil at normal atmospheric temperature through two-step solution-phase reactions for COER to CO. In this special Ag NPs/CuO MNSs heterostructure, the mesoporous CuO NSs with rough edges favored gas infiltration, while decorated Ag NPs expanded the active sites for CO molecule adsorption. Ag NPs endowed Ag NPs/CuO MNSs with good electrical conductivity and promoted the adsorbed CO molecules to obtain electrons from the catalyst. Especially, the Ag-CuO interface stabilized the *COOH intermediate with strong bonding, which is important in boosting COER to CO. The optimal Ag/CuO can catalyze COER to CO with a Faradaic efficiency of 91.2% and a partial current density of 10.5 mA cm at -0.7 V. Moreover, it exhibited prominent catalytic stability, retaining 97.8% of the initial current density and 97.6% of the original Faradaic efficiency for CO after 12 h of testing at -0.7 V. Notably, the Faradaic efficiency of CO on Ag/CuO can retain over 80% in the potential area from -0.6 to -0.9 V, embodying its high selectivity for CO. This work develops precious metal/metal oxide heterostructures with a low precious metal loading for efficacious COER to CO and beyond.