Evolution of the Electronic Properties and Photocatalytic Activity of z-Type g-C3N4@MoS2 Heterostructures Prepared by a One-Step Calcination Method

In the paper, g-C3N4/MoS2 materials were prepared by using a one-step calcination method with Na2MoO4·2H2O and thiourea as precursors at different reaction temperatures and reaction rates. With the reaction temperature changing from 500 to 550 °C, the prepared composites were composed with MoS2 and g-C3N4 nanomaterials, where MoS2 nanosheets were decorated with g-C3N4 nanoflakes; up to 600 °C, the disappearance of g-C3N4 typical features in FT-IR spectra implies that the composites were mainly consistent with MoS2; further up to 700 °C, XRD patterns and Raman spectra revealed that the composites were composed with MoS2 nanosheets. All of the prepared samples were used as photocatalysts for hydrogen production, and the highest H2 production rate of 5.21 mmol·g–1·h–1 was obtained for sample MC500-2 without a noble metal as a cocatalyst; the sample was prepared at 500 °C with a rate of 2 °C/min. The mechanism behind has been explained with band alignments. UPS and valence spectra revealed that the g-C3N4/MoS2 heterostructure in sample MC500-2 is a z-type, which is favorable for the separation of the photogenerated electron–hole pairs. The results will be helpful for the preparation of MoS2 and g-C3N4 composites and their application in photocatalytic hydrogen production.