Synthesis And Photocatalytic Performance Of Ultrathin CdS And Porous BiVO₄ Nanostructures

The nano-semiconductor has shown wide application and good performance in the field of solar photocatalytic water splitting.How to prepare semiconductor photocatalysts with high activity,good stability and low price is the focus of the current research in the field of solar photocatalysis,and also the key to realize its commercialization and popularization.Improving the absorption of light by semiconductor,enhancing the separation efficiency of photogenerated electron hole pairs and increasing the surface reactive sites are the promising approaches to building semiconductor materials with high catalytic activity.Herein,we select CdS and BiVO₄,two kinds of representative metal chalcogenide and oxide,as the research objects because of their abundant raw materials,easy preparation and good visible light photocatalytic performance.We have developed a new method to controllably synthesize a new type of ultrathin semiconductor nanostructure in solar water splitting field and explored the relationship between the morphology,size,nanostructure and semiconductor photocatalytic hydrogen production performance.The main research contents are summarized as follows:?1?We develop the selective cation-exchange induced chemical transformation strategy to synthesize 3D hierarchical ultrathin-branched CdS nanowire arrays?3DHU-CdS?with adjustable branch size by the reaction of the ZnS-amine inorganic-organic hybrid nanosheets with Cd²⁺ions.Benefiting from the unique hierarchical and ultrathin structural features,the as-converted 3DHU-CdS are found to not only be highly active photocatalysts for water-reduction hydrogen evolution,but also be promising photosensitizers for constructing noble-metal-free biomimetic artificial hybrid system.?2?We present a one-pot diethylenetriamine-assisted method for synthesizing ultrathin CdS nanosheets?CdS NSs?with the thickness of².5 nm and their composites with reduced graphene oxide?CdS-NSs/RGO?.A robust and efficient Z-scheme photocatalytic system composed of ultrathin CdS NSs or CdS-NSs/RGO and WO₃ NSs combined through the electrostatic interaction are also rationally designed.The fabricated Z-scheme system shows excellent stability and exhibits relatively stable activity.Special ultrathin and 2D sheets-like structure,electrostatic interaction,proper band structure and assistance of the RGO as a supporting matrix and an electron collector contribute to the effortless transfer of electrons,resulting in the enhanced photocatalytic performance.Furthermore,we also demonstrate that the mediator-free Z-scheme photocatalytic system can be used as a photocathode for photoelectrocatalytic?PEC?H₂ evolution.The work present here may provide a new approach to fabricate the efficient photocatalytic system?3?We report that BiVO₄/NiFe-LDH photoanode with the porous BiVO₄ film as the photon absorber and the nanostructured NiFe-LDH as the oxygen-evolution cocatalyst?OEC?can effectively promote the charge separation and the surface reaction kinetics.The performance of the as-fabricated composite photoanode for PEC water splitting can be further enhanced through incorporating a certain amount of Co²⁺cation into NiFe-LDH as OEC.The as-obtained photocurrent is the highest among un-doped BiVO₄-based photoanodes known to date.The adjustable species and ratios of metal ions in LDHs make the LDHs be the promising candidates as OECs in PEC devices.