Simultaneous facilitation of CO2 adsorption and proton feeding in Bi/Bi2O3 heterostructure nanosheets for enhanced electroreduction of CO2 to formate in a wide potential window

Abstract

Bi-based materials have emerged as highly efficient catalysts for the electroreduction of CO₂ (ERC). However, their practical application is limited by their complex preparation procedures, poor CO₂ adsorption and rate-limiting proton supply, and the lack of an understanding of the fundamental catalytic mechanism. In this study, Bi/Bi₂O₃ heterostructure nanosheet catalysts were designed and synthesised using a facile electrochemical approach. Ex situ and in situ physicochemical characterisation studies, as well as density functional theory calculations, indicated that the Bi/Bi₂O₃ heterostructure leads to the formation of electron-rich Bi, exhibits boosted adsorption of CO₂ and proton feeding, and promotes the formation of a HCOO* intermediate. Benefiting from these advantages, the Bi/Bi₂O₃ nanosheet heterostructure catalyst exhibits an enhanced ERC performance, achieving a high formate current density of 70.27 mA cm⁻² and a formate Faradaic efficiency of >90% over a broad potential window (800 mV) in a H-type cell. It outperformed its single-component counterpart and many other state-of-the-art Bi-based catalysts. In addition, Bi/Bi₂O₃ nanosheets were structurally robust and exhibited a stable performance during the ERC process. Overall, this work sheds light on the interface engineering of Bi catalysts and deepens our understanding of the ERC mechanism based on Bi-based hybrid catalysts.