Synthesis of Doped g-C3N4 Photonic Crystals for Enhanced Light-Driven Hydrogen Production from Catalytic Water-Splitting

Abstract

Dopants are frequently used to improve graphitic carbon nitride (gCN) photoactivity. As a doping source, phosphomolybdic acid (PMA) can activate doping sites inside the gCN lattice, resulting in 2D Mo:P-gCN porous material. However, the gradual loading of the PMA fraction has no systematic improvement in the Mo:P-gCN photoactivity. For improving the optoelectronic properties of Mo:P-gCN, its textural geometry is a controllable parameter that can provide enhanced photonic properties, achievable by shaping its morphology through a crystalline template structure, namely, photonic crystals (PCs). Herein, a doped PC material is made of Mo:P-gCN and PCs and labeled as Mo:P-gCN/PCs. The impact of PCs is highlighted in the structural, electronic, and optical performances of Mo:P-gCN. A well-defined 3D crystalline network is evidenced by microscopic measurements (scanning electron microscopy, AFM, focused ion beam). Mo:P-gCN/PCs shows a hydrogen production rate (750 μmol g⁻¹ h⁻¹) one time higher than Mo:P-gCN and 6 times higher than pure gCN. The synthesis strategy proposed in this work leads simultaneously to the Mo:P codoping effect provided by PMA and the slow photon effect due to the PC structure, offering a novel strategy to improve the gCN photoactivity by simultaneously applying polyoxometalates as modifiers and polystyrene opals as templates.