Dynamic Oxide-Derived Cu Interfaces for Highly Selective Electrochemical CO 2 Reduction

The electrochemical CO 2 reduction activity and selectivity of copper-based electrodes are strongly influenced by their surface phase composition, electronic structure, and stability under the operating conditions. Herein, the Cu electrodes are subjected to controlled oxidation–reduction (Cu-5, Cu-10, and Cu-15), and their structural and electrochemical properties are systematically investigated along with catalytic performance. The spectroscopic characterization confirms that the interaction of Cu 2 O/CuO combined with the dynamically evolving Cu 0 /Cu + interfaces enables favorable electronic pathways. The electrochemical measurements further demonstrate that the Cu-10 exhibits a lower onset potential and superior selectivity for formate compared to Cu-5 and Cu-15. The remarkable performance of Cu-10 highlights the critical role of phase engineering in modulating the reaction pathways and suppressing the competing hydrogen evolution. These findings provide the mechanistic insights and establish the rational guidelines for the design of efficient and robust copper-based CO 2 reduction electrocatalysts that evolve sustainable carbon utilization technologies.