Insight into the Active Sites of N,P-Codoped Carbon Materials for Electrocatalytic CO2 Reduction

Doping heteroatoms in carbon materials is a promising method to prepare the robust electrocatalysts for the carbon dioxidereduction reaction (CO2RR), which is beneficial for sustainable energystorage and environmental remediation. However, the obscure recognitionof active sites is the obstacle for further development of high-efficiencyelectrocatalysts, especially for the N,P-codoped carbon materials. Herein, aseries of N,P-codoped carbon materials (CNP) is prepared with different Nand P contents to explore the relationship between the N/P configurationand the CO2RR activity. As compared with the N-doped carbon materials,the additional P doping is helpful to improve the activity. The optimumN,P-codoped carbon materials (CNP-900) achieve 80.8% CO Faradaicefficiency (FECO) at a mild overpotential of 0.44 V. On the basis of the X-ray photoelectron spectroscopy results, the suitable ratio between pyridinicN and graphitic N and the least P-N content are beneficial for CO2RR.The density functional theory calculations further illustrate that two elementary steps to form*COOH and*CO in CO2RR aredetermined by the graphitic N and pyridinic N configurations, respectively. The existence of the P-N configuration breaks the equilibrium between graphitic N and pyridinic N to suppress the activity