Bi-Sn Oxides for Highly Selective CO₂ Electroreduction to Formate in a Wide Potential Window

The electroreduction of CO₂ into the highly value-added fuel formic acid (HCOOH) has been considered an ideal approach to convert renewable energy and mitigate environmental crisis. SnO₂ electrode is one of the promising candidates to electrocatalytically convert CO₂ to HCOOH, but its poor stability limits its future development and application. In this study, highly stable SnO₂ /Bi₂ O₃ oxide catalysts are obtained by distributing SnO₂ nanoparticles on the surface of Bi₂ O₃ sheets. The XPS spectra revealed an interfacial electronic transportation from Bi₂ O₃ sheets to SnO₂ nanoparticles, which made SnO₂ rich of electrons. The strong interfacial interaction protected the active sites of SnO₂ from self-reduction in CO₂ electroreduction reaction (CO₂ RR), stabilizing SnO₂ species in the composite catalyst even after long-term usage. Calculations based on density functional theory signified that the presence of Bi₂ O₃ favored the adsorption of HCOO* intermediate, improved the CO₂ conversion into HCOOH on SnO₂ /Bi₂ O₃ interface. As a result, the SnO₂ /Bi₂ O₃ catalyst attained high performance on CO₂ RR (the highest FE $$ value of 90 % at -1.0 V vs. RHE), suppressing H₂ evolution reaction (HER) at high potentials. In particular, the selectivity of HCOOH remained above 76 % in a wide potential window (from -1.0 to -1.4 V vs. RHE) and a long duration (12 h).