Study On Design,Synthesis And Performance Of Titanium Dioxide-Based Composite Photocatalysts For Water Reduction

Energy shortage and environmental pollution have restricted the sustainable development of human society,and it is urgent to find renewable and clean energy.The carbon-free combustion products of hydrogen(H2)makes it one of the greenest energy carriers and a major alternative to fossil fuels in future energy supplies.Using inorganic semiconductor materials for solar to hydrogen energy conversion(STH)technology to prepare H2 is an effective solution to solve the above problems.As a semiconductor material with suitable energy band structure,low price,environmental friendliness,non-toxicity and good stability,titanium dioxide(TiO2)is widely used in the field of photocatalytic H2 production.Nevertheless,the limited absorption of light by pure TiO2 and the low separation efficiency of photogenerated electron-hole pairs lead to the low efficiency of STH,which limits its large-scale application.Therefore,promoting the separation and transport of photogenerated charges is the key to realize efficient photocatalytic water splitting for H2 production.Through the introduction of narrow band gap semiconductor and high conductivity materials,charge transfer channels were designed to realize directional migration of electrons and holes in the composite system and the maximum separation of photogenerated charges,so as to achieve the purpose of efficient photocatalytic hydrogen generation.The main research contents are as follows:(1)A highly defective TiO2/MoP/CC(CC represents carbon cloth)composite photocatalyst was synthesized by hydrothermal method,high-temperature calcination and electrophoresis method successively.The material was characterized systematically,and experimental results show that the composite reveals excellent photocatalytic activity for H2 production and long-term cycling stability.On the one hand,CC can provide a large surface area for the growth of the catalyst,thus inhibiting the agglomeration of the catalyst and increasing the contact area between TiO2 and MoP;on the other hand,CC acts as an electron collector,inducing the photogenerated electrons to migrate in the order of TiO2→MoP→CC.In addition,the introduction of defects not only increase the concentration of charge carriers in the material and improve the charge transfer efficiency,but also further promote the separation of photogenerated carriers as electron traps.This part of work is expected to open up a new way to develope new non-powder based photocatalytic system.(2)In order to improve the efficiency of charge separation in TiO2,energy bandmatched MoO2 was introduced for the control of interface engineering,that is to construct heterojunction,and then highly reactive Ni was used as H2 generation cocatalyst to construct Ni/MoO2/TiO2 ternary composite system.The results show that the composite photocatalyst exhibits excellent performance and stability for H2 production.In addition,the influences of the calcination temperature of cocatalyst and single component cocatalyst on the performance of the composite system were discussed.Through analysis,it can be found that only when Ni and MoO2 exist at the same time,the performance of TiO2 can be improved to the greatest extent.The reason is that the highly efficient heterojunction can be formed between TiO2 and MoO2,and the existence of Ni can reduce the overpotential of reaction and improve the charge transfer ability.Therefore,the efficient separation and transfer of photogenerated carriers is the direct factor for the excellent photocatalytic performance of the Ni/MoO2/TiO2 ternary composite system.