In situ reconstructured alloy nanosheets heterojunction for highly selective electrochemical CO2 reduction to formate

Abstract Tin (Sn)‐based materials are expected to realize efficient CO 2 electroreduction into formate. Herein, we constructed a heterojunction by depositing Cu on Cu‐doped SnS 2 nanosheets. During the electrochemical reaction, this heterojunction evolves to a highly active phase of Cu 2 O@Cu 6 Sn 5 while maintaining its two‐dimensional morphology. Specifically, a partial current density of 35 mA cm −2 with an impressive faradaic efficiency of 93 % for formate production was achieved over the evolved heterojunction. In situ and ex situ experiments elucidated the formation mechanism of the Cu₂O@Cu₆Sn₅ heterojunction. Cu₆Sn₅ nanosheets were formed via a stepwise desulfurization process, while Cu₂O was generated through its reaction with hydroxyl radicals. This evolved heterojunction with a high electrochemically active surface area synergistically stabilized the *OCHO intermediate, thereby significantly enhancing the selectivity and activity. Our findings provide insight into the structural evolution process and guide the development of selective electrocatalysts for CO 2 reduction.