A Study On The Interfacial Photogenerated Charge Transfer Behavior Of Nickle-based Cocatalyst/TiO₂ Nanotube Arrays

Energy and environmental are the two major issues that human beings have been facing.As a clean and non-pollution renewable energy,solar energy is considered to be a new type of energy in the 21 st century.Therefore,reasonable and effective use of solar energy to solve the above problems is the hotspot of research in recent years.Semiconductor photocatalyst can realize the conversion of solar energy to clean energy effectively.Among numerous photocatalytic materials,the TiO₂ nanotube arrays?TiO₂ NTAs?have attracted much attention due to their unique physical and chemical properties.However,as an indirect bandgap semiconductor,the pure TiO₂ materials?rutile and anatase phase?also suffer from many defects such as the rapid recombination of photogenerated electron-hole pairs and the low transfer rate of interfacial charge.Recently,the introduction of appropriate cocatalyst is regarded as an effective method to enhance the photocatalytic activity.So far,however,the study of cocatalyst has entered a bottleneck period.The reason is that the introduction of cocatalyst can solve the problem of low transfer efficiency of photogenerated charge in the interface between single photocatalyst and electrolyte,but it also brings new obstacles to the charge transfer at the same time.The transfer of photogenerated charge between the interface of cocatalyst and the photocatalyst becomes another prominent problem.As is known,the photocatalytic reaction is carried out on the surface of the catalyst.In other words,the much more the number of photogenerated charges that can reach the surface of the catalyst and participate in the reaction,the higher the efficiency of overall photocatalytic reaction.Therefore,the effects of the introduction of cocatalyst on the behavior of photogenerated charge is a matter of concern for our design the efficient photocatalysts.Actually,in the process of photocatalytic reaction of composite photocatalyst,there are two main factors that affect the photocatalytic efficiency.One is the transfer process of the photogenerated charges between the cocatalyst and photocatalyst interface?solid-solid interface?,and the other one is the transfer process of the photogenerated charges between cocatalyst and electrolyte interface?solid-liquid interface?.Therefore,the central idea of accelerating the charge transfer between the solid and solid interfaces is to increase the driving force of the interfacial charge transfer.In this work,TiO₂ NTAs modified with different Ni based cocatalysts were used as the research object.And the study of the charge behavior between two interfaces was carried out,which mainly affects the activity of the photocatalyst,by combining the surface photovoltaic technology and the methods of traditional electrochemical measurement in this work.The thesis of the article include the following two parts:1.Study on photogenerated charge behavior between cocatalyst and photocatalysts in NiO/TiO₂ NTAs materials: The charge transfer in the interface between solid and solid is a new problem,which is caused by the introduction of cocatalyst.This problem has an important effect on the activity of the photocatalyst.Therefore,the NiO/TiO₂ NTAs was used as the research object in this part,and the transfer behavior of photogenerated charge between the interface of the Ni O and TiO₂ NTAs was studied.In this work,TiO₂ NTAs were prepared by the method of electrochemical anodization,and NiO were loaded onto the surface of TiO₂ NTAs successfully by chemical impregnation.The results of surface photovoltage and work function measurements show that an interfacial electric field has been formed between the interface of NiO and TiO₂ NTAs.Under the action of the interface electric field,the photogenerated charge are separated effectively.And the favorable hole collection of NiO can also promotes the charge transfer from TiO₂ to NiO,so that the photocatalytic performance of TiO₂ NTAs were improved obviously.Therefore,the central idea of accelerating the charge transfer between the solid and solid interfaces is to increase the driving force of the interfacial charge transfer.2.Study on the photogenerated charge transfer behavior of Ni₃S₂/TiO₂ NTAs between the interface of composite photocatalyst and electrolyte: The transfer of photogenerated charge at the interface of solid-solid is the key to determine the photocatalytic activity.However,the interface of solid-liquid charge transfer is also a problem that cannot be ignored.Therefore,the Ni₃S₂/TiO₂ NTAs was used as the research object in this part,and the transfer behavior of photogenerated charge between solid-solid and solid-liquid interface were studied.In this work,the Ni₃S₂ cocatalyst were supported on the surface of Ti O2 NTAs successfully by two-step hydrothermal method.The measurement of surface photovoltaic provide direct evidence for the effective transfer of photogenerated charge at the interface of Ni₃S₂ and TiO₂ NTAs.On this basis,the traditional electrochemical measurements show that the introduction of Ni₃S₂ can reduce the overpotential of oxygen production and decrease the resistance of charge transfer between solid-liquid interfaces tremendously,thus enhancing the photoelectrocatalytic activity of Ti O2 NTAs Therefore,the cocatalyst with good electrocatalytic activity can reduce the charge transfer resistance between the interface of solid and liquid effectively.The study of the interfacial charge transfer behavior of the cocatalyst/photocatalyst has laid a good theoretical foundation for the cocatalyst selection and construction of composite photocatalyst material.