Reconstruction of Copper Nanoparticles at Electrochemical CO2 Reduction Reaction Conditions Occurs via Two‐step Dissolution/Redeposition Mechanism.

Copper is still the monometallic electrocatalyst of choice for electrochemical reduction of CO2 (ERC) when added‐value products, such as hydrocarbons and alcohols, are desired. However, severe morphological and structural changes are observed upon exposure to the ERC operation conditions. One of the pending questions in the community is what the mechanism behind this reconstruction is. In the present study, pulse‐electrodeposited copper nanoparticles were exposed to different ERC relevant reductive potentials and tracked with identical location scanning electron microscopy (IL‐SEM). This approach provides information on the morphological and structural history and subsequent change of Cu nanoparticles and with that a deep insight into the reconstruction events. With this evidence, we could interpret the observed structural changes as two separate electrochemical processes occurring one after another, namely copper dissolution from pre‐oxidized native nanoparticles and subsequent (electro‐) redeposition of the dissolved copper species in a form of new smaller Cu fragments. [ABSTRACT FROM AUTHOR]