Surface Alloyed-Zn promotes stability of Cu-Au catalysts toward electrochemical CO2 reduction reaction

Abstract

The electrochemical reduction of carbon dioxide (CO2RR) is a subject of great economic and social relevance, as it represents a promising solution for the storage of renewable energy in the form of valuable chemical compounds and fuels. Bimetallic Cu-Au catalysts show great promise in efficient CO2-to-CO electrochemical conversion, particularly within a less Au content. However, the stability issue of Cu-Au catalysts always places obstacles on the long-term CO2RR application due to the metal dissolution issue. Here, we report a trimetallic Cu-Au-Zn catalyst in which a few amounts of Zn are incorporated into the CuAu alloy shell to promote the stability of Cu-Au catalysts for electrochemical CO2RR. The incorporation of a low concentration of Zn not only modifies the CO binding affinity but also alters the catalytic properties of nearby CuAu through geometric and electronic effects. A few amounts of Zn play a vital role in suppressing the surface pits and potentially preventing preferential corrosion at specific sites during electrochemical reaction conditions, thus, the catalyst surface is stabilized. The as-synthesized Cu-Au-Zn catalyst (Zn = 3 at. % and Au < 20 at. %) exhibits a high CO2-to-CO activity, holding a CO faradaic efficiency of 82 % in 0.1 M KHCO3 saturated with CO2 at −0.8 V, and also shows superior stability with no obvious current and selectivity degradation in 10 h, as compared to the Cu-Au counterparts. It is revealed that the surface alloyed Zn significantly alleviates the movement of metal atoms, offers dissolution resistance, and improves both structural and performance stability while retaining excellent CO2-to-CO conversion. These important findings provide a strategy to strengthen the promising Cu-Au CO2RR catalysts with a high noble-metal utilization. More importantly, the addition of few amounts of metals and alloying can promote the stability of functional materials under reaction conditions.