Qun-Zeng Huang,Ji-Chao Wang,Li-Qun Ye,Qian Zhang,Hong-Chang Yao,Zhong-Jun Li
The construction of p–n heterojunction is an efficient strategy to restrain photogenerated charge carriers recombination and enhance the photocatalytic efficiency toward H 2 evolution from water splitting. Herein a novel p–n heterojunction Mn 0.25 Cd 0.75 S/Co 3 O 4 was synthesized via facile hydrothermal method. Photocatalytic H 2 evolution of as-synthesized Mn 0.25 Cd 0.75 S/Co 3 O 4 composites in the absence of noble metal co-catalysts under visible light irradiation ( λ ≥ 400 nm) was investigated. The results demonstrated that photocatalytic H 2 evolution of Mn 0.25 Cd 0.75 S was significantly enhanced by loading Co 3 O 4 nanoparticles . It was confirmed that 0.48 wt% of Co 3 O 4 loading content achieved the highest H 2 evolution rate of 25.71 mmol/g/h, which was about 5.35 times higher than that of pure Mn 0.25 Cd 0.75 S. The remarkably improved photocatalytic activity could be attributed to the formation of the p–n junction at the interface between Mn 0.25 Cd 0.75 S and Co 3 O 4 , effectively promoting interfacial charge transfer and separation. This work revealed that the p–n heterojunction Mn 0.25 Cd 0.75 S/Co 3 O 4 may be a promising candidate for efficient energy conversion.
Photocatalytic selective organic transformations coupled with hydrogen (H 2 ) generation under anaerobic conditions is a promising alternative to tackle the challenges of global energy scarcity and green synthesis. In this work, we report the synthesis and application of Ni doped Mn 0.25 Cd 0.75 S (MCS-Ni) composites for efficient selective dehydrocoupling of amines into imines and H 2 . The optimal MCS-Ni composite displays markedly enhanced activities for imines and H 2 generation, which are 7.9 and 11.5 times as high as those of pristine MCS, respectively. The Ni doping modulates the electronic structure of MCS, which improves the light-harvesting abilities and inhibits the recombination of photo-generated electron-hole pairs, thereby remarkably improving the photocatalytic performance of the MCS-Ni composite. Furthermore, the electron paramagnetic resonance (EPR) technique reveals that carbon centered radicals are the critical intermediates in the amine oxidation reaction. This work is promising to provide inspiration towards the rational construction of metal doped semiconductor composite photocatalysts with effective utilization of photo-generated electrons and holes for the coproduction of clean H 2 fuel and high-value added chemicals in a collaborative photoredox reaction.
Qun-Zeng Huang,Yan Xiong,Qian Zhang,Hong-Chang Yao,Zhong-Jun Li
Development of noble metal-free and highly efficient co-catalyst that endows semiconductor materials with high performance is of great significance towards enhancing photocatalytic H 2 evolution. Herein, a series of novel Mn 0.25 Cd 0.75 S/MoS 2 composites have been successfully prepared by a facile one-step hydrothermal method . The photocatalytic activity of the as-prepared photocatalysts for H 2 production from water splitting under visible-light irradiation (λ ≥ 400 nm) was investigated. The results showed that Mn 0.25 Cd 0.75 S/MoS 2 heterostructured composites have a higher photocatalytic activity than Mn 0.25 Cd 0.75 S, implying that the intimate interfacial contact between Mn 0.25 Cd 0.75 S and MoS 2 facilitates electron transfer from Mn 0.25 Cd 0.75 S to MoS 2 , thus promoting the separation of photogenerated charge carriers and providing more active sites for H 2 evolution reaction. The introduction of noble metal-free MoS 2 co-catalyst led to a remarkable improvement in the photocatalytic H 2 evolution activity of Mn 0.25 Cd 0.75 S, and the content of MoS 2 in composite had an important influence on the photocatalytic activity. It was confirmed that 0.7 wt% of MoS 2 loading content achieves a maximum photocatalytic H 2 evolution rate of 12.47 mmol g −1 h −1 , which was much higher than that of Mn 0.25 Cd 0.75 S and also slightly higher than that of Mn 0.25 Cd 0.75 S/Pt (1.0 wt%). This work revealed that low cost MoS 2 could replace noble metal Pt as a highly efficient co-catalyst in enhancing the photocatalytic activity of semiconductor materials.
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