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

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.