| Photocatalysis is a new green energy technology with great potential,in which photocatalyst plays a key role in the process of solar energy conversion to clean energy.Therefore,the focus of photocatalytic research is to seek efficient and stable catalytic materials.Metal oxide semiconductor materials have been widely studied and used in the field of photocatalysis because of their advantages such as low cost,easy preparation,strong photo-oxidation and reduction ability.ZnO has the advantages of good exciton binding energy,easy morphology and structure regulation,low toxicity,low cost,high stability and recoverability,which makes it stand out among many semiconductor materials.However,due to the high photoelectron-hole recombination rate of ZnO,its application in the field of photocatalysis is limited.Thereby,it is urgent to modify ZnO for improving photocatalytic activity.In this thesis,the surface structure of ZnO is regulated by polyhydroxy fructose to introduce oxygen vacancy on the surface,which would expand the range of light absorption,enhance the oxidation capacity of photocatalyst,and achieve efficient photocatalytic degradation of high concentration of organic pollutants.ZnO-ZnS heterostructure was constructed by a simple thermal treatment to realize the high activity of photocatalytic decomposition of water for hydrogen production.In addition,the three-dimensional ordered macroporous ZnO-ZnS heterostructure was constructed to improve mass transfer and provide more surface reaction sites,reduce the recombination of photogenerated carriers.First of all,polyhydroxy fructose was used as the template.A very small amount of fructose(2×10-5 g L-1)was added to the surface to modify the hydroxyl group and synthesize ZnO single crystal nanosheets via a wet chemical synthesis method.ZnO sheets with rich surface oxygen vacancy was formed during the removement of fructose at high temperature.Fructose-regualted ZnO nanosheets with more positive valence band position can provide more surface reaction sites generate more photogenerated holes with stronger oxidation capacity,and greatly improving their photocatalytic activity.Compared with unmodified ZnO,Fructose-regualted ZnO single crystal nanosheets oxygen-vacancy can efficiently degrade high concentration of phenol and other organic pollutants,and exhibit photocatalytic activity for hydrogen production.In order to improve the weak activity of ZnO on photocatalytic hydrogen production,ZnS with strong photoreducing ability was introduced to construct the ZnS-ZnO heterostructure based on the direct Z-mode carrier transport mechanism.The surface of ZnS nanoparticles was partially oxidized into ZnO by a simple heat treatment to construct the ZnS-ZnO heterostructure.Owing to the part of ZnS reacted with oxygen to form ZnO,therefore in the interface to form relatively stable fusion,the electronic-hole can rapidly transfer between the interface of ZnS and ZnO and improve the transmission rate of carrier.In addition,the Z-scheme mechanism can prolong the lifetime of the carrier obviously.The ZnS-ZnO heterostructure exhibits a substantially improved photocatalytic hydrogen production rate.Due to the agglomeration phenomenon of the thermally converted ZnS-ZnO heterostructures,the reaction liquid cannot completely contact with the heterojunction,which is not conducive to photocatalytic hydrogen production.In order to improve the efficiency of the bulk phase fully participating in the photocatalytic reaction,provide more surface reaction sites,and enhance its photocatalytic hydrogen production activity,we constructed three-dimensional ordered macroporous（3DOM）ZnO using polymethyl methacrylate beads as template.The 3DOM ZnO-ZnS heterostructure was constructed by partial vulcanization of 3DOM ZnO.Compared with ZnO without macroporous structure and bulk ZnS-ZnO,3DOM ZnO-ZnO heterostructure shows higher photocatalytic performance for hydrogen production. |
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