Hao Wang,Qian Liu,Tingting Ji,Ruiyang Zhao,Lu Li,Jishu Han,Lei Wang
The construction of heterojunction is an effective and controllable method to improve the photocatalytic decomposition of water to produce hydrogen by semiconductor photocatalyst . In this paper, NiCo 2 S 4 yolk-shell nanospheres and Mn 0.8 Cd 0.2 S nanoparticles were synthesised by solvothermal and hydrothermal methods , and then Mn 0.8 Cd 0.2 S nanoparticles were loaded onto the surface of NiCo 2 S 4 to form a dense Z-scheme heterojunction . Without precious metals as cocatalysts, the maximum hydrogen production of the optimized Mn 0.8 Cd 0.2 S/NiCo 2 S 4 reached 21.41 mmol·g −1 ·h −1 . The morphology, structure and optical properties of the prepared samples were characterized, and the experimental results and theoretical calculations showed that Mn 0.8 Cd 0.2 S/NiCo 2 S 4 with Z-scheme heterojunction could improve the efficiency of photocatalytic hydrogen production by effectively transferring and separating the photogenerated electrons and holes.
A series of novel visible light-responsive Mn 0.8 Cd 0.2 S/g-C 3 N 4 hybrid materials with different g-C 3 N 4 contents were synthesized via a facile hydrothermal method. The obtained Mn 0.8 Cd 0.2 S/g-C 3 N 4 composites displayed highly efficient photocatalytic activities for H 2 evolution from aqueous solutions containing sacrificial reagents (Na 2 S and Na 2 SO 3 ) under visible light ( λ > 420 nm) even without noble metal co-catalysts. The highest H 2 evolution rate of 4.0 mmol h −1 g −1 (with an apparent quantum efficiency of 4.1% at 420 nm) was achieved on the Mn 0.8 Cd 0.2 S/g-C 3 N 4 (10 wt%) sample, which was about 3.40 times higher than that of pure Mn 0.8 Cd 0.2 S. The enhanced photocatalytic activity of Mn 0.8 Cd 0.2 S/g-C 3 N 4 composites should be attributed to the well-matched band structure and intimate contact interfaces between Mn 0.8 Cd 0.2 S and g-C 3 N 4 , which led to the effective transfer and separation of the photogenerated charge carriers. In addition, the Mn 0.8 Cd 0.2 S/g-C 3 N 4 photocatalysts showed good stability during the photocatalytic water splitting to hydrogen under visible light. A possible mechanism of the enhanced photocatalytic activity of Mn 0.8 Cd 0.2 S/g-C 3 N 4 was also proposed.
In this work, we demonstrated the polyvinylpyrrolidone-assisted solvothermal synthesis of three-dimensional (3D) flowerlike Mn0.8Cd0.2S microspheres assembled from nanosheets. The as-synthesized products were characterized by using various methods including powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microcopy/selected area electron diffraction, elemental mapping, X-ray photoelectron spectroscopy, inductively-coupled plasma emission spectroscopy, N2 adsorption–desorption, UV-vis diffuse reflectance spectroscopy, photoluminescence spectroscopy and photoelectrochemical experiments. The possible formation mechanism of the unique structures was discussed. The resultant 3D flowerlike Mn0.8Cd0.2S architectures exhibit better photocatalytic activities for H2 evolution and CO2 reduction under visible light irradiation than the Mn0.8Cd0.2S nanoparticles. A hydrogen evolution rate of 3560.3 μmol g−1 h−1 and a CH3OH production rate of 10.7 μmol g−1 h−1 are achieved on the flowerlike Mn0.8Cd0.2S microspheres. Several possible reasons for the enhanced photocatalytic activity of the Mn0.8Cd0.2S hierarchical microspheres have been taken into consideration. In addition, the Mn0.8Cd0.2S microspheres are stable during the reaction and can be used repeatedly.
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