Enhancing H2 evolution with Mo-N Bonding in Hierarchical Periodic Macroporous Photocatalyst of S-doped g-C3N4 and N-doped MoS2

Abstract

Heterojunctions constructed by traditional methods often result in random stacking of materials, leading to lattice mismatch, which adversely affects the extraction and transfer of photo-generated carriers and, in turn, hampers light utilization efficiency. In this work, we report a novel heterojunction comprising alternating S-doped g-C₃N₄ (SCN) and N-doped MoS₂ (NMS), bridged by Mo–N covalent bonds within hierarchical periodic macroporous (HPM) walls. This heterojunction is synthesized by co-pyrolyzing dicyandiamide, thiourea, and ammonium molybdate. Transient reflectance photoluminescence measurements reveal that the Mo–N covalent bonds serve as “fast tracks” for electron transfer from SCN to NMS, significantly enhancing the charge separation efficiency. Additionally, the well-defined spatial separation of photo-induced carriers, coupled with the efficient mass transfer within the HPM structure, promotes superior carrier utilization. Thanks to the synergistic effect of HPM structures and the bridged Mo–N bonds, the optimized HPM NMS/SCN-1.3 sample exhibits a remarkable H₂ evolution rate of 473.3 µmol g⁻¹ h⁻¹ under visible light irradiation, which is approximately 163 and 19 times higher than bulk g-C₃N₄ (BCN) and HPM SCN, respectively. This work offers valuable insights into the design of HPM heterojunctions composed of co-catalysts and host catalysts, paving the way for enhanced photocatalytic H₂ evolution.