Boosting electrochemical CO₂ reduction by strong electronic interaction at the interface of Bi/SnO₂ heterostructures

SnO₂-based materials are promising electrocatalysts for the conversion of CO₂ to formate however increasing their activity further is challenging due to the suboptimal CO₂ adsorption and activation capacity. The interfacial engineering has proven effective in modulating the electronic structure and adsorption behavior of electrocatalysts. Herein, a heterostructure Bi/SnO₂ was constructed for the CO₂ electroreduction to formate in which a formate Faraday efficiency of 94.9% and single-pass carbon efficiency of 40.3% were achieved at -1.0 V versus reversible hydrogen electrode in 1.0 M KOH. During a 30-hour stability test, the current density was nearly constant without a significant decrease while the formate Faraday efficiency was maintained around 90%. This remarkable activity is attributed to the strong electronic interaction arising from p-p orbital coupling at the Bi/SnO₂ interface, according to the experimental and theoretical investigations. The computational insights suggest that the p-p orbital coupling promotes the electron transfer from Bi to SnO₂ and optimizes the adsorption strength of the intermediate (*OCHO) to enhance the catalytic activity. The formation of *OCHO during formate generation was confirmed by the in situ attenuated total reflectance surface-enhanced infrared absorption spectroscopy. This work might contribute key insights into the mechanisms underlying activity enhancement via strong electronic interaction between dual p-block metal catalysts.