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

A step-scheme MnWO4/g-C3N4 heterojunction is successfully synthesized for efficient enhancing photocatalytic H-2 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 H-2 generation achieving to 2,820.2 mu mol/g in 3 h, which is 3.74 times higher than the bare g-C3N4. Therefore, the improved photocatalytic H-2 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. (C) 2021 Elsevier Ltd. All rights reserved.