Self-assembled three-dimensional flowerlike Mn0.8Cd0.2S microspheres as efficient visible-light-driven photocatalysts for H2 evolution and CO2 reduction

Abstract

In this work, we demonstrated the polyvinylpyrrolidone-assisted solvothermal synthesis of three-dimensional (3D) flowerlike Mn_0.8Cd_0.2S 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 Mn_0.8Cd_0.2S architectures exhibit better photocatalytic activities for H₂ evolution and CO₂ reduction under visible light irradiation than the Mn_0.8Cd_0.2S 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 Mn_0.8Cd_0.2S microspheres. Several possible reasons for the enhanced photocatalytic activity of the Mn_0.8Cd_0.2S hierarchical microspheres have been taken into consideration. In addition, the Mn_0.8Cd_0.2S microspheres are stable during the reaction and can be used repeatedly.