Unraveling Structure Sensitivity in CO2 Electroreduction to Near-Unity CO on Silver Nanocubes

The renewable-energy-powered electrochemical CO2 reduction reaction (CO2RR) provides an attractive strategy to simultaneously address the energy storage and environmental issues through the synthesis of carbon-neutral fuels. This study unravels structure sensitivity of ultrasmall Ag nanocubes with lengths below 25 and 70 nm (L25- and L70-Ag-NCs) enclosed completely by the (100) facet toward an efficient CO2RR to CO. The ultrasmall L25-Ag-NCs deliver a remarkably larger current density, a significantly higher Faraday efficiency (FE) of near-unity, and a comparably higher energy efficiency of 64.0% as well as a better stability of ∼18 h as compared to L70-Ag-NCs, Ag nanoparticles, and bulk Ag. More importantly, CO generation initiates at an ultralow overpotential of 146 mV, accompanied with a remarkably high onset CO FE of 59.6%, further demonstrating the excellence of L25-Ag-NCs for highly active and selective CO2RR. Density functional theory calculations, the percentages of various catalytically active sites, and how the architecture of NCs affecting the active sites as well as the partial density of states were analyzed; the results reveal that the essential origins credited for the enhanced catalytic activity and near-unity CO selectivity over L25-Ag-NCs at lowered η originate from the particular nanostructure, where energetically favorable active sites toward CO2RR are maximally introduced through accurately synthesizing the specific nanostructure enclosed by a certain facet.