Selective CO 2 Electroreduction to Formate on Polypyrrole-Modified Oxygen Vacancy-Rich Bi 2 O 3 Nanosheet Precatalysts by Local Microenvironment Modulation.

Challenges remain in the development of highly efficient catalysts for selective electrochemical transformation of carbon dioxide (CO 2 ) to high-valued hydrocarbons. In this study, oxygen vacancy-rich Bi 2 O 3 nanosheets coated with polypyrrole (Bi 2 O 3 @PPy NSs) are designed and synthesized, as precatalysts for selective electrocatalytic CO 2 reduction to formate. Systematic material characterization demonstrated that Bi 2 O 3 @PPy precatalyst can evolve intoBi 2 O 2 CO 3 @PPy nanosheets with rich oxygen vacancies (Bi 2 O 2 CO 3 @PPy NSs) via electrolyte-mediated conversion and function as the real active catalyst for CO 2 reduction reaction electrocatalysis. Coating catalyst with a PPy shell can modulate the interfacial microenvironment of active sites, which work in coordination with rich oxygen vacancies in Bi 2 O 2 CO 3 and efficiently mediate directional selective CO 2 reduction toward formate formation. With the fine-tuning of interfacial microenvironment, the optimized Bi 2 O 3 @PPy-2 NSs derived Bi 2 O 2 CO 3 @PPy-2 NSs exhibit a maximum Faradaic efficiency of 95.8% at -0.8 V (versus. reversible hydrogen electrode) for formate production. This work might shed some light on designing advanced catalysts toward selective electrocatalytic CO 2 reduction through local microenvironment engineering.