Design And Construction Of Nano TiO₂ Photocatalyst And Its Performance For Overall Water Splitting

It is of great value to construct a photocatalytic water splitting system with hydrogen peroxide as the oxidation product and hydrogen as the reduction product.Compared with the traditional hydrogen/oxygen overall water splitting system,this system produces hydrogen peroxide with high value-added while preparing hydrogen,and avoids the problem of products separation and the explosive hazard of the hydrogen-oxygen mixture.This system has obvious advantages in reaction kinetics and is a promising solution for photocatalytic water splitting.The development of suitable catalysts is the key for the study of hydrogen/hydrogen peroxide photocatalytic system.This paper discusses the application of nano TiO₂ photocatalysts in this system,and analyzes the effects of the catalysts’structure characteristics on this system.Anatase TiO₂ nano-photocatalyst and nano-mesoporous TiO₂ mixed crystal（brookite-rutile）photocatalyst were studied in this system.The synthesis rules,morphology and crystal structure,photoelectrochemical properties and surface chemical properties were investigated.The activity and mechanism of both catalysts in photocatalytic water splitting of hydrogen and hydrogen peroxide production was analyzed.It was found that both TiO₂ photocatalysts exhibited the performance of producting hydrogen and hydrogen peroxide simultaneously by water splitting,and achieved excellent hydrogen production rates.In the system with Pt/TiO₂（anatase）as catalyst,the generation rates of H₂ and H₂O₂ can reach 7.41 and 5.10μmol·mg^-1·h^-1,respectively,which is much higher than the commercial anatase system which possesses the similar morphology.In the system with nano-mesoporous TiO₂ mixed crystal as catalyst,with the assistance of Pt nanoparticles,the efficiencies of H₂ and H2 production can reach to 9.46μmol·mg^-1·h^-1 and 3.29μmol·mg^-1·h^-1,respectively.In the analysis of the catalytic reaction mechanism,it was found that the hydroxyl radical is an important intermediate in the reaction system,and the hydrophilicity and the hydroxyl groups adsorption capacity of the surface of samples are the key factors affecting the photocatalytic performance.Hydrogen peroxide is formed by the condensation of hydroxyl radicals formed by the oxidation of hydroxyl groups adsorbed on the catalyst surface.At the same time,we explored the influence of various conditions during the synthesis of nano-mesoporous mixed-crystal TiO₂photocatalyst,and screened out the best synthesis conditions.These research results show that the construction of highly efficient photocatalytic water splitting system with hydrogen and hydrogen peroxide as productions has good research and application prospects.This work provides new ideas and strategy for construction of a photocatalytic system with excellent water splitting performance,as well as precise and controllable synthesis of nano-TiO₂ photocatalyst.