Thermal-Treated α-Bi2O3 Electrocatalyst for Efficient CO2 Electroreduction toward Formate

The electrochemical CO2 reduction reaction (CO2RR) provides a renewable avenue to convert CO2 to value-added fuels and chemicals. Bismuth (Bi)-based electrocatalysts are known as promising candidates for CO2RR to formate (HCOO–), yet their performance is frequently limited by structural reconstruction during operation, resulting in reduced activity and selectivity. This work describes a thermal treatment approach to tuning the catalytic chemistry of α-Bi2O3 for CO2RR. A thermally optimized Bi-400 electrocatalyst achieves a high Faradaic efficiency of 93.0% for HCOO– at −0.95 V vs RHE, along with good stability over 70 h. Through detailed structural and mechanistic studies, it is revealed that the preserved Bi–O motifs in Bi-400 facilitate CO2 activation and modulate the binding energy of the *OCHO intermediate, thereby enhancing both activity and selectivity toward HCOO– production. This study would provide an in-depth understanding of the selective formation of HCOO– products on Bi-based electrocatalysts in CO2RR.