Low-Overpotential CO₂ Electroreduction to HCOOH Using Electrodeposited Dendritic Bi-Ce Alloys

Electrochemical carbon dioxide reduction (CO₂RR) to value-added products such as formic acid (HCOOH) is a promising approach. Among various electrocatalysts for CO₂ reduction, bismuth-based materials stand out as a superior candidate for formic acid production, demonstrating high Faradaic efficiency, excellent stability, and remarkable selectivity under mild reaction conditions, but they still face issues, such as requiring high overpotentials. This study aims to enhance the performance of Bi by alloying with Ce. Bi-Ce alloys were prepared by electrodeposition from water-ethylene glycol solution. The electrodeposition behaviors of Bi and Ce were studied, and the Bi-Ce alloys with different atomic ratios can be easily obtained by adjusting the deposition potential. The electrodeposited Bi-Ce thin films exhibited excellent performance for the CO₂RR in a CO₂-saturated 0.1 M KHCO₃ solution. The Bi96.5Ce3.5 alloy exhibits exceptional electrocatalytic performance for CO₂ reduction to formic acid, achieving a high Faradaic efficiency (FE_HCOOH > 94%) across a broad potential window (-0.7937 V to -0.9937 V vs RHE). Notably, a peak FE_HCOOH of 99.1% is attained at a relatively low overpotential (-0.8437 V vs RHE) while maintaining excellent stability over prolonged electrolysis (12 h), underscoring its potential as a highly efficient and durable catalyst for formic acid production.