Time-resolved operando insights into the tunable selectivity of Cu–Zn nanocubes during pulsed CO2 electroreduction†

Pulsed electrochemical CO₂ reduction (CO₂RR) has emerged as a facile way to alter the product selectivities toward desired multicarbon products, but so far, it has been mainly applied to monometallic Cu-based electrodes, which suffer from stability issues. Here, ZnO-decorated Cu₂O nanocubes were exposed to various pulsed CO₂RR treatments to uncover the effect of the redox transitions of both metals on the dynamic catalyst structure and composition and its link to their catalytic function. An increase in the ethanol selectivity was observed once pulsed into the oxidation regime of zinc, while the parasitic hydrogen evolution drastically increased once pulsed into the oxidation regime of Cu. By employing time-resolved operando X-ray absorption spectroscopy, X-ray diffraction, and surface-enhanced Raman spectroscopy, we could follow the dynamically induced interplay between Zn oxide, CuZn alloy, metallic Zn and metallic Cu formation, and the coverage of co-adsorbed hydroxide and *CO. Our study highlights the relevance of zinc oxide and an increased OH coverage for the enhancement of the catalyst selectivity toward ethanol.