Engineering Phosphorus Doping Graphitic Carbon Nitride for Efficient Visible-Light Photocatalytic Hydrogen Production

Modulating the electronic structure and surface properties of graphitic carbon nitride (g-C3N4) by chemically phosphorus doping is an effective strategy for improving its photocatalytic performance. However, in order to benefit from practical applications, the cost-effectiveness, efficiency, and optimization of the doping level need to be investigated further. Herein, we report a structural doping of P into g-C3N4 by in situ polymerization of the mixture of dicyandiamide (DCDA) and phosphorus pentoxide (P2O5). As an alternative to previous studies that used complex organic phosphorus precursors or post-treatment strategies, this work proposed a one-pot thermal polycondensation method that is low-cost, scalable, and enables controlled phosphorus substitutions at carbon sites of the g-C3N4 heptazine structure. Most of the structural features of g-C3N4 were well retained after doping, but the electronic structures and light harvesting capacity had been effectively altered, which provided not only a much better charge separation but also an improvement in photocatalytic activity toward H2 evolution under irradiation of a simulated sunlight. The optimized sample with P-doping content of 9.35 at.% (0.5PGCN) exhibited an excellent photocatalytic performance toward H2 evolution, which is over 5 times higher than that of bulk g-C3N4. This work demonstrates a facile one-step in situ route for producing high-yield photocatalysts using low-cost commercial precursors, offering practical starting materials for studies in solar cells, polymer batteries, and photocatalytic applications.