Unraveling the Selectivity of Acidic CO<sub>2</sub> Reduction in CuAg Tandem Electrocatalysts.

Chen, Yi; Ye, Taiping; He, Zhizhong; Liu, Ya; Guo, Youhong · Nano Lett · 2026

basic_science · Level V

Where this comes from

Abstract

Acidic electrocatalytic CO<sub>2</sub> reduction (CO<sub>2</sub>R) offers compelling advantages in carbon efficiency and long-term stability. However, mechanistic insights into tandem electrocatalysis in acidic media remain limited due to the difficulty of resolving the coupled dynamics of intermediates at reactive interfaces. Here, we unveil a "CH<sub>4</sub>-C<sub>2+</sub>-CO" selectivity evolution across composition-graded CuAg tandem catalysts as Ag fraction increases from single-atom alloy to subnanoclusters to nanoparticle clusters. The surface composition simultaneously governs *CO intermediate binding strength and reorients the interfacial water microenvironment to direct local reaction pathways. The product selectivity of CuAg tandem catalysts is dictated by the regulation of *CO spillover from Ag to adjacent Cu domains, favoring either C-C coupling or CO desorption. Our findings establish a unified *CO/*H-centric mechanistic framework for tandem CO<sub>2</sub>R electrocatalysis in acidic media, providing compositional design principles for selective multicarbon product generation.