Passivation of Cu nanosheet dissolution with Cu2+-containing electrolytes for selective electroreduction of CO2 to CH4

Abstract

Electrocatalytic conversion of carbon dioxide (CO₂) to methane (CH₄) has drawn great attention for solving the problem of global warming by reducing greenhouse gases and recycling carbon resources. Among reported Cu-based catalysts, Cu nanosheets (Cu NSs) with a highly exposed (111) facet are beneficial for converting CO₂ to CH₄. However, the stability issue of Cu NSs, due to their dissolution, severely limits their performance and practical application in electrocatalytic CO₂ reduction. Here, we report a method to effectively passivate the dissolution of Cu NSs by adding an appropriate amount of Cu²⁺ in the electrolyte, which improves the selectivity and stability of CO₂ reduction to CH₄. Structural characterization and CO₂ reduction tests indicate that the Cu NSs maintain the exposed (111) facet and thus maintain the efficient reduction of CO₂ to CH₄ in the electrolyte containing an appropriate Cu²⁺ concentration. The Cu NSs exhibit a high CH₄ selectivity of ∼70% and a high stability of ∼60% for ∼10 h. This work indicates that a moderate amount of Cu²⁺ in the electrolyte can passivate the Cu dissolution and increase the stability of Cu electrodes, providing a new perspective for achieving better stability of catalysts in the future.