Phosphorus-doped Isotype g-C₃N₄/g-C₃N₄: An Efficient Charge Transfer System for Photoelectrochemical Water Oxidation

Constructing isotype g-C₃N₄/g-C₃N₄ heterojunction is an approach to improve the efficiency of g-C₃N₄ towards solar-assisted oxidation of water. Such functional configuration can effectively overcome the intrinsic drawback of rapid charge recombination of g-C₃N₄. Here, a modified g-C₃N₄, with homogeneous phosphorus doping, is prepared in this work through a phosphide-involved gas phase reaction. The resulting P-g-C₃N₄ displays altered electronic structure, including upshifted band edge potential, narrowed band gap and improved electronic conductivity. These features allow P-g-C₃N₄ as an outstanding candidate to form isotype junction with pristine g-C₃N₄. As expected, the accelerated charge separation and migration in target junction is validated by various measurements. The optimized isotype g-C₃N₄/P-g-C₃N₄ heterojunction achieves a photocurrent as high as 0.3 mA cm⁻² at 1.23 V vs RHE (AM 1.5G, 100 mW cm⁻²), representing 8-fold's enhancement compared with pristine g-C₃N₄. The present strategy for constructing g-C₃N₄-based isotype heterojunction networks is found effective for large-scale manufacturing.