Selenium-Doped Hierarchically Porous Carbon Nanosheets as an Efficient Metal-Free Electrocatalyst for CO_2 Reduction

摘要

Electrochemical carbon dioxide reduction reaction (CO2RR) provides a promising pathway for both decreasing atmospheric CO2 concentration and producing valuable carbon-based fuels. To explore efficient and cost-effective catalysts for electrochemical CO2RR is of great importance, but remains challenging. Se-doped carbon nanosheets (Se-CNs) with a micro-, meso-, and macroporous structure are proposed for electrochemical CO2RR. Such an electrocatalyst combines the advantages of Se optimized active sites, hierarchical pores for facilitating reactant or ion penetration, transport and reaction, and large surface area for more accessible active sites. This Se-CNs electrocatalyst exhibits over 11-times enhanced partial current density of CO than the CNs without Se doping and high selectivity (90%) for CO2 electroreduction to CO at a low potential of -0.6 V versus the reversible hydrogen electrode (vs RHE). Density function theoretical calculations reveal that the Se introduction in CNs lowers the free energy barrier of CO2RR and inhibits hydrogen evolution reaction effectively, thus improving the selectivity for CO2 reduction to CO. This work presents a new member of the metal-free electrocatalyst family, which is easily prepared, low cost, adjustable, and highly efficient for CO2RR.