Synthesis Of Monoclinic CdS Nanorods And Orthorhombic InVO₄ Nanoparticles For The Photocatalytic Hydrogen Production Under Visible Light

Hydrogen energy is considered as one of the ideal fuels for the future. Solar light photocatalytic hydrogen production has attacted much attention for directly converting from solar energy to chemical energy and simultaneously solving the environmental pollution problem. Developping highly efficient visible-light-response photocatalysts is the key factor for accelerating photocatalytic hydrogen production. This paper selects CdS and InVO4 as the research object, which respectively represent sulfide and oxide system with visible light photocatalytic activity, and focuses on the impact of crystal structure and particle size on the photocatalytic activity. Details are as follows:First, monoclinic CdS nanorods were synthesized by the hydrothermal method, using CdSO4 as the cadmium source and mercaptoacetic acid as the sulfur source respectively. The morphology and crystal structure of as prepared samples were characterized by SEM and XRD. The visible light photocatalytic activities for hydrogen production were evaluated with Na2S and Na2SO3 as sacrificial agents. The results show that CdS nanofibers were obtained both at 120℃and 160℃; compared with samples obtained at 160℃, CdS obtained at 120℃have a smaller grain size and crystallinity, and a higher photocatalytic activitiy, and they transformed into the cubic phase in the photocatalytic reaction, while samples obtained at 160℃transformed into the hexagonal phase in the photocatalytic reaction. The transformation reason was explained from the relationship between structure parameters, such as grain size, crystallinity, and crystal structure, and solubility product constants.Second, orthorhombic InVO4 nanoparticles were synthesized by the hydrothermal method using InCl3 and NH4VO3 as the raw materials. The impacts of hydrothermal temperature and pH value on the morphology, structure and visible light photocatalytic activity of InV04 were systematic studied. It is found that the pH value has important impact on the phase structure in the hydrothermal reaction. With the pH value increased, the content of InVO4 gradually decreased while the content of In(OH)3 gradually increased; Pure InV04 nanoparticles can be obtained with pH value of 4, and the size of InVO4 nanoparticles decreases with the increase of hydrothermal temperature. Sample obtained at 165℃has the best catalytic activity owning to its suitable particle size and band gap(2.2 eV).