3D core–shell porous-structured Cu@Sn hybrid electrodes with unprecedented selective CO2-into-formate electroreduction achieving 100%

Cu-based catalysts are exceptionally advantageous for the electrochemical CO2 reduction reaction (CO2RR) to fuels and chemical products utilizing clean and renewable energy. However, most tend to yield a diversity of hydrocarbon products along with the H-2 evolution side reaction. We reveal how a 3D core-shell porous-structured Cu@Sn hybrid electrode can lead to an unprecedented selective CO2 electroreduction to HCOO-. Such an advantageous architecture is assembled via an in situ electrodeposition protocol using a dynamic hydrogen bubble template, rendering an enlarged electrode surface area when evaluated as an electrode material for the CO2RR. Notably, the best performing electrode, i.e., Cu@Sn-(1), achieved a reduction current density of 55 mA cm (2) at -1.33 V vs. RHE, and an extremely encouraging Faradaic efficiency of 100% at an applied potential -0.93 V vs. RHE, accompanied by a partial current density of 16.52 mA cm(-2). Moreover, it manifested a remarkably stable operation for over 15 hours of continuous electrolysis in aqueous KHCO3 solution. Numerically solving mass transfer equations and the Butler-Volmer equation show how the optimized presence of granular structured Sn on the surface of Cu was found to be the key for enhancing the HCOO- selectivity and the mass activity.