Self-supported copper selenide nanosheets for electrochemical carbon dioxide conversion to syngas with a broad H2-to-CO ratio

Production of syngas from carbon dioxide (CO2) and water (H2O) is greatly attractive but very challenging for accomplishing tuneable/wide range of H2-to-CO ratios at current density. Herein, the anion-regulated self-supported Cu3Se2 with a hierarchical structure of nanosheet-assembled fibers, enabling multiple copper valence states and abundant in situ formed copper boundaries simultaneously regulating electrochemical CO2 reduction reaction (CO2RR) and H2 evolution reaction (HER). As a consequence, the delicate design of Cu3Se2 catalyst results in an outstanding electrocatalysis of syngas generation with a tuneable/wide range of H2-to-CO ratios (0.8 to 6.0), and high turnover frequency of 1303 h-1, which can achieve a high current density much higher than Cu foam and stable electrolysis with negligible attenuation of Faraday efficiency and current. The superior performance is attributed to the multiple copper valence states for activation of CO2, and the abundant boundaries for modifying the binding energy of intermediate for *COOH formation and *CO desorption and hydrogen adsorption for HER process. Therefore, the design of anion-regulated electrocatalysts with self-supported Cu3Se2 nanosheet-assembled fibers show great potential for the investigation of value-added chemicals/fuels from CO2RR.