Deterministically designed regular Ag nanopatterns as co-catalysts on Cu to elucidate the role of Ag-Cu contact interface in electrocatalytic CO₂ reduction reaction

Abstract

The electrochemical reduction of CO2 to hydrocarbons offers a promising solution to transform greenhouse emissions into valuable chemicals. Copper is a promising catalyst, but the electrocatalytic formation of C2+ products requires simultaneous adsorption of various intermediates and charge transfer steps for C-C bond formation. As such, a large portion of the surface is constantly occupied by multiple species and the supply of fresh reaction intermediates becomes a limitation. Therefore, a strategy for CO2R on Cu is adding a second catalyst in close proximity that supplies specific reaction intermediates to the Cu sites where they are converted to higher hydrocarbons. Ag is especially opportune as a co-catalyst, since it has a high selectivity to form CO, a key reaction intermediate in the pathway to C2+ products. In this work the synergistic electrocatalytic behavior of Ag with Cu is investigated using regularly nanopatterned Ag lines as co-catalyst on planar Cu electrodes. UV nano-imprint lithography allowed to systematically vary pattern dimensions, distance between Ag and Cu as well as the Ag-Cu contact points, while keeping the total Ag:Cu area constant at ∼50:50%. With decreasing distance between two Ag lines from 400 to 200nm and doubling Ag-Cu contact interface, the synergistic effect between Ag and Cu was shown by an increased product selectivity to C2H4. Larger Ag line distance resulted in increased CH4 and H2 formation. This work shows how nanopatterning can guide fundamental investigations leading to the deterministic design of electrodes with two (or more) catalysts for CO2 electroreduction with tailored product selectivity.