Preparation Of Cadmium Sulfide Modified By Cobalt Sulfide And Its Application In Photocatalytic Hydrogen Evolution From Water Splitting

Hydrogen energy possesses high combustion efficiency and environment friendly,and it is considered as green energy.Photocatalytic water splitting is viewed as the most promising field at synthesis of hydrogen due to low consumption and no pollution.Hence many researchers pay widespread attention on photocatalytic hydrogen evolution.The core of photocatalytic water splitting focuses on the design and synthesis of catalytic nano-materials.Cadmium sulfide is one of the most widely studied photocatalysts owing to the good absorption for visible light（2.3 eV）and appropriate conduction band.However,CdS has many defects,such as low absorption efficiency,severe recombination of charge carriers.Therefore,some normal methods for enhancement of activity and stability for photocatalytic hydrogen evolution include phase and morphology adjustment,doping with metal and non-metal elements,fabrication of heterojunctions and the use of co-catalysts.The addition of a co-catalyst is seen as one of the most efficient method for photocatalytic hydrogen evolution,it can not only offer many active sites,decrease of activity energy,but alsocapture photoelectron to facilitate charge separation and transfer.However,the rare resource,high price and difficult synthetic process of traditional noble metal co-catalysts hamper their usage.Therefore,it is extremely meaningful to explore non-noble metal cocatalyst coupled with CdS.Based on it,this work used a non-noble metal cobalt sulfide（CoS_x）as co-catalyst and enhanced the activity of CdS for photocatalytic hydrogen evolution by controlling composition,structure and exposed facet of co-catalyst.So innovative research results are listed as follows:1.By controlling defferent molar ratio of Co and S to synthesize defferent exposed specific facets of Co₉S₈,and studying CdS modified by above Co₉S₈ make influence for photocatalytic water splitting.Among of synthesized Co₉S₈,when the molar ratio of Co and S was 1:2,CdS modified by the exposed facet（311）and（511）of Co₉S₈ can get optimal hydrogen evolution rate for photocatalysis(15.45 mmol·g^-1·h^-1).Meanwhile,co-catalyst Co₉S₈ not only enhance the efficiency of CdS for visible light,but also the exposed facet（311）and（511）of Co₉S₈ is favorable to separation of charge carrier for CdS.2.Controllable preparation CoS₂ nanoparticles anchored on CdS nanorods by an in-situ solvothermal method.The intimate interface and‘electron bridge’were built between CoS₂and CdS,and the photogenerated electron can transfer from CdS nanorods to CoS₂.The optimal CoS₂/CdS composites exhibit outstanding photocatalytic activity in H₂ production under visible light(⁵8 mmol·g^-1·h^-1),which is about 19 times that of CdS nanorods and 3times that of 1 wt%Pt/CdS under the same conditions.Co-catalyst CoS₂ can not only serve as electron trap to enhance the separation of charge carrier due to its noble metallic nature（relevant result can be proved by DFT calculation）,but also offer more active sites for reactant and product.