Abstract
We elucidate the role of subsurface oxygen on the production of C(2) products from CO(2) reduction over Cu electrocatalysts using the newly developed grand canonical potential kinetics density functional theory method, which predicts that the rate of C(2) production on pure Cu with no O is ∼500 times slower than H(2) evolution. In contrast, starting with Cu(2)O, the rate of C(2) production is >5,000 times faster than pure Cu(111) and comparable to H(2) production. To validate these predictions experimentally, we combined time-dependent product detection with multiple characterization techniques to show that ethylene production decreases substantially with time and that a sufficiently prolonged reaction time (up to 20 h) leads only to H(2) evolution with ethylene production ∼1,000 times slower, in agreement with theory. This result shows that maintaining substantial subsurface oxygen is essential for long-term C(2) production with Cu catalysts.