Structural Evolution of Phosphorus Species on Graphene with a Stabilized Electrochemical Interface

Phosphorus doping is an effective approach to tailor the surface chemistry of carbon materials. In this work, two-dimensional graphene, as a simplified model for all sp² hybrid carbon allotropes, is employed to explore the surface chemistry of P-doped carbon materials. Thermally reduced graphene oxide, with abundant residual oxygen functionalities, is doped by phosphorus heteroatoms through H₃PO₄ activation, followed by passivation in an inert atmosphere. The structural evolution of the phosphorus species in the carbon lattice during the thermal treatment is systematically studied by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and Raman spectroscopy with the assistance of first-principles calculations. The C₃-P═O configuration is identified as the most stable structure in the graphene lattice and plays a key role in stabilizing the electrochemical interface between the electrode and electrolyte. These features enable an electrode based on P-doped graphene to exhibit an enlarged potential window of 1.5 V in an aqueous electrolyte, a remarkable improved cycling stability, and an ultralow leak current. Therefore, this contribution provides insights for designing phosphorus-doped carbon materials toward electrocatalysis, energy-related applications, and so forth.