Stabilizing Sn/SnO2 Mott–Schottky Heterojunction on Biomass-Derived Carbon Boosting Highly Selective and Robust Formate Production for Electrochemical CO2 Reduction

The oxidation states of metal-based electrocatalysts have been proved to be beneficial to improve the product selectivity for electrochemical CO2 reduction (ECO2R), while it usually suffers from decay due to the reductive environment leading to performance deterioration. Herein, we construct robust Sn/SnO2 Mott–Schottky heterojunction on biomass (sodium alginate)-derived carbon by a facile heat treatment method, which demonstrates high selectivity and robustness for formate production by ECO2R. The wide partial current density of formate from 4.4 to 220.8 mA cm–2 with excellent formate selectivity (Faradaic efficiency (FE) > 90%) can be achieved on Sn/SnO2 heterojunction electrocatalyst in a gas diffusion flow cell, which is one of the widest among Sn-based electrocatalysts. Moreover, the Sn/SnO2 heterojunction electrocatalyst achieves a remarkably high total energy efficiency of 68.1% for formate production in a gas diffusion full cell. In situ Raman spectra and density functional theory simulations illustrate that the electrons transfer from SnO2 to Sn, which facilitates the formation of *OCHO intermediate meanwhile impeding the competitive hydrogen evolution reaction (HER), leading to the high selectivity and robustness for ECO2R.