Controlled vertical growing of Bi2O3 nano sheets on diatomite disks and its high visible-light photocatalytic performance

Abstract

3D stacking structures of Bi2O3 nano sheets with β-Bi2O3-like lattice were successfully built up on natural diatomite disks by pre-controlling the surface charge of diatomite before hydrothermal treatment. Diatomite was selected due to its abundant in-situ biomasses, which provided an ideal interface position between porous diatomite and loaded Bi2O3. Three different pre-treating processes, carbothermal reduction, air calcination, and hydrogen peroxide pretreatment, have been compared in order to reveal the role of in-situ biomasses (and their products) of natural diatomite in improving the photocatalytic performance of Bi2O3/diatomite composites. The samples were characterized by DSC, XRD, SEM, TEM, XPS, UV–vis, surface charge analysis, photoelectrochemical property and photocatalytic activity testing. The results show that Bi2O3/diatomite composites display highly photocatalytic activities and reliable recycling performances for both Rhodamine B and levofloxacin under visible light, due to strong interaction between Bi2O3 and diatomite revealed by XPS, UV–vis and XRD. The lattice structure of superior photocatalyst, β-Bi2O3-like phase with interlaminar constitution water, is stabilized by diatomite carrier through hydrothermal synthesis. Suitable hydrogen peroxide pretreatment of in-situ biomasses provides ideal carbonaceous substance and surface charge level for diatomite carries, leading to vertical growth of Bi2O3 nano sheets and larger surface area of Bi2O3/diatomite composites. Hydrogen peroxide pretreatment narrows the band gap of Bi2O3 from 2.93 eV to 2.72 eV greatly, on the contrary the carbothermal reduction treatment widens the band gap to 3.32 eV instead. As revealed by capture testing, for Bi2O3/diatomite composites, the ·OH and holes are the main active species during photocatalytic process. The best sample Bi2O3/50 °C-HD, which has 3D stacking structures of Bi2O3 nano sheets, displays narrower band gap and less recombination rate between photon-generated carriers.