Surface reorganization of oxide-derived Cu-M (M = Zn, Ag) bimetallic catalysts in CO2 electroreduction environment

Abstract

As the oxide-derived copper-based electrodes gain continuously more recognition for their great performance in catalyzing CO2 reduction reaction (CO2RR), it is important to define which surface features stand behind their catalytic properties. The presented research explores the surface reorganization of Cu, CuAg10, and CuZn37 passivated materials caused by the reductive environment of CO2RR. It is shown that the presence of Ag constituent has a marginate influence on the mechanism of passive layer growth on copper, whereas Zn changes it in a significant manner. Therefore, the synthesis parameters need to be adjusted differently for both bimetallic systems. The passivation of both Cu and CuAg surfaces provided the best surface area development in the most concentrated electrolyte (3 M NaOH) and CuZn in the least concentrated solution (1 M NaOH). Additionally, after subjecting the selected passivated electrodes to CO2RR conditions, a thorough surface analysis was performed to inspect the influence of Ag and Zn on the characteristic features of the oxide-derived electrodes identified in the modified surfaces. It was found that the more noble Ag component slightly lowers the mixed valance nature of the Cu electrode, however, it provides Ag species that are beneficial for CO2RR selectivity. On the other hand, the CuZn material indicates lower resistance to reduction by suppressed surface area development which leads to a decrease in oxygen vacancies and the amount of oxidized Cu species.