Study On Promoting Photocatalytic Performance Of Semiconductor By Cocatalyst

Environmental pollution has become a serious crisis with the use of traditional fossil energy sources,coal,oil,natural gas etc.Developing new clean energy instead of fossil energy has been attracted considerable interest in worldwise.Hydrogen energy is regarded as one of the most potential clean new energy sources in the 21st century because of its green,environmental protection,non-pollution,high efficiency,cleanliness and renewability.At present,there are three main methods to prepare hydrogen energy:recombination of fossil energy,hydrogen production by electrolysis of water and hydrogen production by photocatalysis.However,the reorganization of fossil energy can not only alleviate the dependence on fossil energy,but also cause environmental pollution;Although hydrogen production from electrolytic water is a kind of hydrogen energy from water,it needs to consume electric energy and has high cost.Hydrogen production by photolysis of water is the most environmentally friendly way to produce hydrogen energy from solar energy by semiconductor;In order to obtain ideal photocatalytic hydrogen production efficiency,it is necessary for ideal semiconductors to absorb a wide range of sunlight spectra,to transport and separate photoelectrons and holes easily,and to have strong redox ability to drive water splitting.After years of research,great progress has been made in the production of hydrogen from photolysis water,but the efficiency of photolysis water is still not high enough to meet the requirements of commercialization.Therefore,the effective separation of photogenerated electrons and holes through modification of semiconductors,such as nano-structure of semiconductors to increase the specific surface area of photocatalytic reaction,semiconductor recombination,co-catalyst modification and precious metal deposition,is of great significance for improving the photocatalytic performance of semiconductors.This paper is devoted to the design of metal phosphides as co-catalysts,precious metal deposition and semiconductor morphology control to improve the photocatalytic performance of semiconductors.A series of composite nanomaterials with novel morphology and excellent photocatalytic performance were constructed by template method,hydrothermal method and spin coating method.It mainly includes the following three contents.(1)The bowl-like structure of TiO2 was successfully synthesized by spin-coating method and template method,and Au nanoparticles were deposited on the bowl-like structure of TiO2 by evaporation-plating method.The experimental results show that the photoelectric properties of the bowl-like structure of TiO2 modified by Au nanoparticles have been improved.(2)Based on the bowl-like structure of TiO2,TiO2 with both nano-array and opal inverse structure was successfully synthesized by hydrothermal method.Ni2P quantum dots and opal inverse structure of TiO2 nano-array were compounded by spin-coating method to form composite catalyst.Successful application in photoanode,it showed excellent catalytic performance in photoelectrochemical hydrogen production.Under constant bias and alkaline conditions of 0.6 vs RHE,the photocurrent density reached 1.95 mA/cm2.The mechanism of this photocurrent was discussed in detail?(3)Bulk g-C3N4 was synthesized from melamine by calcination.Bulk g-C3N4 was peeled off by hydrothermal method to form g-C3N4 nanosheets.Finally,Co2P quantum dots were grown on g-C3N4 nanosheets by in-situ growth method.The composite catalyst was successfully applied to hydrogen production by photolysis of water and showed excellent hydrogen production performance.Its hydrogen yield was as high as 4850 ?mol/g1/h1.In summary,the semiconductor is modified by means of adjusting the morphology and structure of semiconductor materials,depositing noble metals,modifying semiconductors with promoters and compounding semiconductors,so as to broaden the optical absorption range of semiconductors,effectively realize the migration,separation and transmission of photogenerated electrons and holes,and make the photogenerated carriers give full play to their redox properties.It provides new perspectives and ideas for commercialization of photocatalytic hydrogen production.