Nanoconfined Tin Oxide within N-Doped Nanocarbon Supported on Electrochemically Exfoliated Graphene for Efficient Electroreduction of CO₂ to Formate and C1 Products

Developing low-cost and effective electrocatalysts for electrochemical reduction of CO2 (CO2ER) is critical to CO2 conversion and utilization. Herein, we report a novel two-dimensional (2D) confined electrocatalyst composed of core–shell structured tin oxide nanoparticles (NPs) encapsulated into N-doped carbon (NC) supported on electrochemically exfoliated graphene (SnO2⊃NC@EEG) prepared by in situ carbonization of a 2-methylimidazole/SnO2 complex@poly(vinyl pyrrolidone) (PVP)-modified EEG precursor. The SnO2 NPs with an average size of ∼10 nm are confined in the NC shells with a thickness of 0.7 nm derived from 2-methylimidazole. The resulting 2D confined electrocatalyst significantly enhances the CO2ER performance with a small onset potential of −0.45 V, and high Faradic efficiencies of 81.2 and 93.2% for HCOO– and C1 products at −1.2 V, respectively, which is far superior to other reported SnO2/carbon-based CO2ER hybrids. The superb CO2ER catalytic activity of the SnO2⊃NC@EEG has resulted from the positive effect of N dopants and a strong confinement effect, which significantly expedites the CO2 adsorption associated with charge transfer from the NC to SnO2 NPs during CO2ER electrocatalysis.