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

Abstract

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.