Alloying as a Strategy to Boost the Stability of Copper Nanocatalysts during the Electrochemical CO 2 Reduction Reaction.

Copper nanocatalysts are among the most promising candidates to drive the electrochemical CO 2 reduction reaction (CO 2 RR). However, the stability of such catalysts during operation is sub-optimal, and improving this aspect of catalyst behavior remains a challenge. Here, we synthesize well-defined and tunable CuGa nanoparticles (NPs) and demonstrate that alloying Cu with Ga considerably improves the stability of the nanocatalysts. In particular, we discover that CuGa NPs containing 17 at. % Ga preserve most of their CO 2 RR activity for at least 20 h while Cu NPs of the same size reconstruct and lose their CO 2 RR activity within 2 h. Various characterization techniques, including X-ray photoelectron spectroscopy and operando X-ray absorption spectroscopy, suggest that the addition of Ga suppresses Cu oxidation at open-circuit potential (ocp) and induces significant electronic interactions between Ga and Cu. Thus, we explain the observed stabilization of the Cu by Ga as a result of the higher oxophilicity and lower electronegativity of Ga, which reduce the propensity of Cu to oxidize at ocp and enhance the bond strength in the alloyed nanocatalysts. In addition to addressing one of the major challenges in CO 2 RR, this study proposes a strategy to generate NPs that are stable under a reducing reaction environment.