pH effects on the electrochemical reduction of CO (2) towards C 2 products on stepped copper

Abstract

We present a microkinetic model for CO (2) reduction (CO (2) R) on Cu(211) towards C 2 products, based on energetics estimated from an explicit solvent model. We show that the differences in both Tafel slopes and pH dependence for C 1 vs C 2 activity arise from differences in their multi-step mechanisms. We find the depletion in C 2 products observed at high overpotential and high pH to arise from the 2 nd order dependence of C-C coupling on CO coverage, which decreases due to competition from the C 1 pathway. We further demonstrate that CO (2) reduction at a fixed pH yield similar activities, due to the facile kinetics for CO 2 reduction to CO on Cu, which suggests C 2 products to be favored for CO 2 R under alkaline conditions. The mechanistic insights of this work elucidate how reaction conditions can lead to significant enhancements in selectivity and activity towards higher value C 2 products.