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

Abstract

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 (FE_CO) 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.