The electrochemical reduction of CO2 in acidic media offers the advantage of high carbon utilization, but achieving high selectivity to C2+ products at a low overpotential remains a challenge. We identified the chemical instability of oxide-derived Cu catalysts as a reason that advances in neutral/alkaline electrolysis do not translate to acidic conditions. In acid, Cu ions leach from Cu oxides, leading to the deactivation of the C2+-active sites of Cu nanoparticles. This prompted us to design acid-stable Cu cluster precatalysts that are reduced in situ to active Cu nanoparticles in strong acid. Operando Raman and X-ray spectroscopy indicated that the bonding between the Cu cluster precatalyst ligand and in situ formed Cu nanoparticles preserves a high density of undercoordinated Cu sites, resulting in a C2H4 Faradaic efficiency of 62% at a low overpotential. The result is a 1.4-fold increase in energy efficiency compared with previous acidic CO2-to-C2+ electrocatalytic systems.
This work was financially supported by the Ontario Research Foundation: Research Excellence Program, the Natural Sciences and Engineering Research Council (NSERC) of Canada, and TotalEnergies SE. J.L. was supported by the National Research Foundation of Korea (NRF) funded by the Korea government (MSIT) (RS-2024-00333848). M.Z. acknowledges the funding support through the Camille Dreyfus Teacher-Scholar Award and the Yale Center for Natural Carbon Capture. W.N. gratefully acknowledges financial support from the Swiss National Science Foundation (SNSF) Postdoctoral Mobility Fellowship (no. P500PN_202906).
