Photo-assisted separation of noble-metal-free oxidation and reduction cocatalysts for graphitic carbon nitride nanosheets with efficient photocatalytic hydrogen evolution

The dual cocatalysts photocatalytic heterostructures are beneficial for water splitting. Here we report a simple photo-assisted synthesis of novel g-C3N4/Co3O4/MoS2 heterojunction with low-cost Co3O4 (oxidation) and MoS2 (reduction) cocatalyst separately deposited onto g-C3N4 nanosheets. Driven by the synergy between Co3O4 and MoS2, the photocatalytic H2 evolution (PHE) activity of g-C3N4/Co3O4-1.9/MoS2-0.9 under visible light irradiation is about 885, 25.6 and 18.2 times better than those for g-C3N4, g-C3N4/Co3O4-1.9 and g-C3N4/MoS2-0.9, respectively, and is also higher than those of g-C3N4 based heterojunctions decorated by MoS2, dual MoS2- and other metal sulfides-based cocatalysts. The g-C3N4/Co3O4-1.9/MoS2-0.9 exhibits stable PHE in the recycle experiment and in various real water matrices. Detail characterization reveals that rapid electron-hole separation and charge species transferring through both Z-scheme and Type-I routes contribute to the improved PHE. With this synthetic strategy, the reduction cocatalyst can be extended to NiS (CoS), and the acquired g-C3N4/Co3O4-1.9/NiS (CoS) also possesses synergistically efficient PHE.