Qian Liu,Wenqian Luan,Xingrong Zhang,Ruiyang Zhao,Jishu Han,Lei Wang
The design of a low-cost, efficient and durable co-catalyst for hydrogen evolution is of great significance for improving photocatalytic activity. In this work, a NiMoP 2 /Cu-ZnS composite photocatalyst was prepared by in-situ growth of NiMoP 2 on the surface of copper-doped zinc sulfide (Cu-ZnS). The test results showed that the hydrogen production rate of the optimized NiMoP 2 /Cu-ZnS under visible light irradiation was significantly improved. Among them, NiMoP 2 /Cu-ZnS-1 exhibited the highest photocatalytic activity (5.13 mmol·g −1 ·h −1 ), which was 2.47 times that of Cu-ZnS and maintained good stability during the reaction. The improvement of hydrogen production performance of the photocatalyst was mainly attributed to the synergistic effect of Cu-ZnS and co-catalyst NiMoP 2 . The ohmic contact formed between Cu-ZnS and NiMoP 2 could improve the separation efficiency of photogenerated carriers and reduce the overpotential of H 2 evolution. Besides, NiMoP 2 was found to provide the active site for the reduction reaction, and accelerate the transfer efficiency of photogenerated electrons. This strategy opens up a new way for the construction of co-catalyst modified semiconductor materials to improve the photocatalytic hydrogen production rate.
Weixin Li,Qing Liu,Zhongxuan Yin,Yongqing Ma,Ganhong Zheng,Chuhong Zhu,Zhenxiang Dai,Meiling Wang
The photocatalytic conversion of CH 4 into value added liquid products in high yield has always been a huge challenge due to unavoidable peroxidation. Here, a kind of Cu/ZnS/ZnO x -550 Z type heterojunction is designed for photocatalytic CH 4 oxidation into C1 products (including CH 3 OH, CH 3 OOH and HCHO) by O 2 through the synergistic catalysis of multiple mechanisms. The CH 4 photooxidation reaction at 30 °C yields 56 mmol g −1 of C1 oxygenated products during 8 h, which exhibits a much higher value than those reported in recent studies. In situ Fourier transform infrared spectroscopy, electron spin resonance spectroscopy, X-ray photoelectron spectroscopy, electrochemical measurements and density functional calculation are used to comprehensively clarify the underlying photocatalytic mechanism. It indicates that in situ formed singlet oxygen ( 1 O 2 ) not only plays vital roles in triggering CH 4 photooxidation to C1 products, but also suppresses products peroxidation by inhibiting ·OH formation. The incorporated Cu transforms the ZnS/ZnO heterojunction from type II to Z -scheme, enhances light absorption, and, together with oxygen vacancies, regulates the electronic structure of the catalyst, thereby facilitating the adsorption and dissociation of 1 O 2 , and ultimately achieving high efficiency of CH 4 photooxidation.
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