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

We present a microkinetic model for CO reduction (CO R) on Cu(211) towards C products, based on energetics estimated from an explicit solvent model. We show that the differences in both Tafel slopes and pH dependence for C vs C activity arise from differences in their multi-step mechanisms. We find the depletion in C products observed at high overpotential and high pH to arise from the 2 order dependence of C-C coupling on CO coverage, which decreases due to competition from the C pathway. We further demonstrate that CO reduction at a fixed pH yield similar activities, due to the facile kinetics for CO reduction to CO on Cu, which suggests C products to be favored for CO 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 products.