Bifunctional Nb-N-C atomic catalyst for aqueous Zn-air battery driving CO2 electrolysis

Abstract

Designing efficient and cost-effective bifunctional catalysts is desirable for carbon dioxide and oxygen reduction reactions (CO2RR and ORR) to address carbon neutralization and energy conversion. Herein, a bifunctional CO2RR and ORR catalyst for aqueous Zn-air battery (ZAB) self-driving CO2RR electrolysis is developed using atomically dispersed niobium anchored onto N-doped ordered mesoporous carbon (Nb-N-C). The Nb-N-C atomic catalyst demonstrates aqueous CO2RR activity with CO Faradaic efficiency up to 90%, ORR activity with a half-wave potential of 0.84 V vs. reversible hydrogen electrode, and ZAB activity with a peak power density of 115.6 mW cm−2, owing to the high Nb atom-utilization efficiency and ordered mesoporous structure. Furthermore, two-unit ZABs in series, serving as the power source for the self-powered CO2 electrolysis system, continuously convert CO2 to CO with average productivity of 3.75 µmol h−1mgcat-1 during the first 10 h. Moreover, theoretical calculations exhibit that atomic Nb anchored to N-doped carbon can form Nb-N coordination bonds, effectively reducing the energy barriers of potential-determining *COOH for CO2RR and *O formation for ORR. [Figure not available: see fulltext.]