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Photocatalysis is one of the most promising technologies in wastewater treatment. Efficient degradation under visible light and the recovery capability of the photocatalyst are crucial in real-word applications. Herein, M−type SrFe12O19 was integrated into the surface of flowerlike MoS2 microsphere via the hydrothermal method. As-prepared SrFe12O19/MoS2 composite photocatalyst has effective visible light response and magnetic recovery ability. The SrFe12O19/MoS2 composite achieved 97% degradation rate for methylene blue under visible light. The photocatalytic reaction rate of the SrFe12O19/MoS2 composite was nearly twice that of pure MoS2. Transient steady-state fluorescence spectrometry and electrochemical spectrometry revealed that an appropriate amount of SrFe12O19 effectively improves the charge transfer rate and accelerates photoinduced charge carrier separation. The possible photocatalytic degradation mechanism of the SrFe12O19/MoS2 composite with the p–n heterojunction was also examined.

Density functional theory was used to study the adsorption of H2 and H and electronic properties of single atom Cu modified Fe (1 1 1) including the Cu adsorption and substitution models. The adsorption ability of H2 and H on Cu modified Fe (1 1 1) could be weakened by the weak adsorption sites provided by Cu atom, Cu occupying the strong adsorption sites of Fe (1 1 1), and weak adsorption of H2 on Fe adjacent Cu, respectively. The analysis of electronic properties and crystal orbital Hamilton population of Fe H bonds indicates that when Cu acts on Fe (1 1 1), the partial electrons of Fe can transfer to adjacent Cu, which weakens the bonding interaction between Fe and the adsorbed H2 and H and then weakens adsorption of Fe (1 1 1) as following: (1) the more electrons Cu atom obtains, the weaker it adsorbs H2 and H, (2) the more electrons Fe atom loses, the weaker it adsorbs H while there is an optimum charge point for H2. Therefore, the adsorption, dissociation of H2 and the catalytic activity of hydrogen-related reactions on Fe catalysts can be regulated by Cu modification, providing important information to further explore catalytic mechanism of syngas conversion reaction on Cu modified Fe catalysts.

The adsorption and dissociation of H2, the migration ability of H atom, as well as the competition relationship between adsorption or deoxidation of H2 with increasing of H adsorption coverage on the Fe3O4 (1 1 1)-Fetet1 and (0 0 1)-B surfaces were systematically studied by DFT + U method. The adsorption energy and the optimal dissociation barrier of H2 on two Fe3O4 surface is about 0.04 eV and 1.0 eV, respectively. The surface O site is the most favorable adsorption site for H and the dissociated H2 is adsorbed on the adjacent surface O atoms. When H coverage is low, H preferentially adsorbs to the most stable O sites with the maximum adsorption heat. With the increasing of H coverage, the adsorption heat gradually decreases. When H coverage approaches saturated coverage, H2 reacted with surface O to form H2O become more favorable than direct adsorption. The phase diagrams of H adsorption/deoxidation at different temperature and pressure ranges were calculated. It can be found that the reduction of surface O become more favorable with the increasing of H coverage. The results indicate that the degree of reduction difficulty of surface O can be controlled by changing the coverage of H by adjusting the reaction condition.