Manganese tungstate/graphitic carbon nitride S-scheme heterojunction for boosting hydrogen evolution and mechanism exploration

Abstract

A step-scheme MnWO4/g-C3N4 heterojunction is successfully synthesized for efficient enhancing photocatalytic H2 evolution by coating MnWO4 nanobars on layered g-C3N4. Valence band X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy and electron paramagnetic resonance have been used to measure work function and band alignment accurately, which evidently demonstrate the formation of S-scheme heterojunction. As a result, the optimal 5%MnWO4/g-C3N4 exhibits a 16.51% of apparent quantum efficiency at 400 nm and enhanced H2 generation achieving to 2,820.2 μmol/g in 3 h, which is 3.74 times higher than the bare g-C3N4. Therefore, the improved photocatalytic H2 generation performance can be attributed to the formation of S-scheme heterojunction, which not only facilitates the separation and migration of photogenerated charge carriers but also increases light absorption efficiency and specific surface area.