Pseudocapacitance Facilitates the Electrocatalytic Reduction of Carbon Dioxide

Electroreduction of CO2 to value-added products is a promising strategy for CO2 reuse, where copper has a unique ability to produce oxygenates and C2+ products. Unfortunately, the electronic factors making copper so unique are unknown, which limits the ability to design improved catalysts. By combining in situ surface-sensitive X-ray resonant photoelectron spectroscopy with density functional theory calculations, the complex electronic structure of copper is uncovered during the electrocatalytic reduction of CO2. It is found that the pseudocapacitive charging of copper, produced by the incorporation of protons and electrons into the subsurface, facilitates the activation of CO2, while simultaneously increasing the barrier for H-H coupling. The net result is that cathodic pseudocapacitive charge suppresses the hydrogen evolution reaction and promotes the production of hydrocarbons and oxygenated products on copper. These results represent a new paradigm in the understanding of CO2 reduction, highlighting the key role of pseudocapacitive charge in the reaction. Using operando X-ray resonant photoelectron spectroscopy and density functional theory calculations, it is found that the pseudocapacitive charging of copper facilitates the electrocatalytic electroreduction of CO2 at the same time that the barrier for the H-H coupling is increased. The pseudocapacitive charging is ruled by the super abundant vacancy, Cu3VacHx clusters (x = 1-6), formation mechanism induced by hydrogen. image