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 dioxide reduction reaction (CO2RR), which is beneficial for sustainable energy storage and environmental remediation. However, the obscure recognition of active sites is the obstacle for further development of high-efficiency electrocatalysts, especially for the N,P-codoped carbon materials. Herein, a series of N,P-codoped carbon materials (CNP) is prepared with different N and P contents to explore the relationship between the N/P configuration and the CO2RR activity. As compared with the N-doped carbon materials, the additional P doping is helpful to improve the activity. The optimum N,P-codoped carbon materials (CNP-900) achieve 80.8% CO Faradaic efficiency (FECO) at a mild overpotential of 0.44 V. On the basis of the X-ray photoelectron spectroscopy results, the suitable ratio between pyridinic N 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 are determined 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.