Mesoporous NiFe2O4@g-C3N4-based p-n Heterostructures for Boosting Solar-Driven Photocatalytic Dye Degradation and Hydrogen Evolution.

Abstract

Mass-fraction-optimized heterojunction composites featuring precisely engineered interfaces and mesoporous structures are crucial for improving light absorption, minimizing electron-hole recombination, and boosting overall catalytic efficiency. Herein, highly efficient mesoporous-NiFe2O4@g-C3N4 heterojunctions were developed by embedding p-type NiFe2O4 nanoparticles (NPs) within n-type porous ultrathin g-C3N4 (p-uCN) nanosheets. The optimized NiFe2O4@g-C3N4, loaded with 20wt% magnetic counterparts, exhibits exceptional photocatalytic methylene blue degradation, achieving the highest performance in both photocatalytic and photo-Fenton processes with rate constants of 0.062 and 0.161 min⁻¹, respectively. These performance metrics are 1.3 and 2.55 fold higher than p-uCN (0.048 and 0.063 min⁻¹) and 51.6 and 17.4 fold higher than NiFO (0.0012 and 0.009 min⁻¹). Notably, mp-NiF@uCN-20% with 1.0 wt% of Pt loading achieves the highest H2 evolution rate of 2294 µmolg⁻¹h⁻¹, which is 3.72, 1.52, and 13.49 times higher than that of pure CN, p-uCN, and NiFO, respectively. The enhanced performance is corroborated by increased surface area, improved separation of charge carriers, and effective charge transfer, which enables simultaneous reduction and oxidation processes. Further, the magnetic nanocomposite exhibits remarkable stability even after multiple runs, indicating their reusability. The experimental findings emphasize the importance of p-n heterojunctions, interfacial band alignment, and mesoporous architecture in enhancing the photocatalytic efficiency of NiFe2O4@g-C3N4 nanocomposites.