Confinement of an alkaline environment for electrocatalytic CO(2) reduction in acidic electrolytes

Acidic electrochemical CO(2) reduction reaction (CO(2)RR) can minimize carbonate formation and eliminate CO(2) crossover, thereby improving long-term stability and enhancing single-pass carbon efficiency (SPCE). However, the kinetically favored hydrogen evolution reaction (HER) is generally predominant under acidic conditions. This paper describes the confinement of a local alkaline environment for efficient CO(2)RR in a strongly acidic electrolyte through the manipulation of mass transfer processes in well-designed hollow-structured Ag@C electrocatalysts. A high faradaic efficiency of over 95% at a current density of 300 mA cm(−2) and an SPCE of 46.2% at a CO(2) flow rate of 2 standard cubic centimeters per minute are achieved in the acidic electrolyte, with enhanced stability compared to that under alkaline conditions. Computational modeling results reveal that the unique structure of Ag@C could regulate the diffusion process of OH(−) and H(+), confining a high-pH local reaction environment for the promoted activity. This work presents a promising route to engineer the microenvironment through the regulation of mass transport that permits the CO(2)RR in acidic electrolytes with high performance.