Effects Of Interface Layer On Photocatalyst Of NaTaO₃:La Composite Film And Its Performance Of Photocatalytic Water Splitting

With the rapid development of the economy,problems such as energy shortage and environmental pollution have become one of the great challenges facing humankind.Therefore,in order to mitigate the energy crisis and reduce environmental pollution,it is urgent to find clean and recyclable energy.Hydrogen energy,as a clean and low-carbon secondary energy with wide application,convenience and storage,has attracted worldwide attention.Second,in order to reduce the cost of hydrogen production,many scientists use a wide range of solar energy as a primary source of hydrogen production has become a current research focus,and the use of semiconductor catalysts to produce hydrogen and oxygen from water is one of the most ideal technologies.As the photocatalyst is the core material in the process of hydrogen production by photolysis of water,people are constantly exploring high-quality photocatalysts.Among semiconductor photocatalysts,NaTaO₃ with perovskite structure has caused extensive research by scholars in various countries due to its relatively high stability and excellent photocatalytic performance under ultraviolet light irradiation.In order to further improve the photolysis water activity of NaTaO₃ catalyst,the structure with sequence ladder was formed on the surface of NaTaO₃ by doping La.While,traditional powder photocatalysts have the following defects:in the process of hydrogen production from photolysis water,the powder photocatalyst needs to be dispersed in the water to participate in the reaction,which makes the powder photocatalytic material dispersed in the liquid.And the dispersed catalyst pollutes water resources,making it difficult to recycle and reuse;Second,a mixture of hydrogen and oxygen is produced during the photocatalytic decomposition of water,and it is difficult to directly separate hydrogen and oxygen;Finally,during the reaction process,hydrogen and oxygen production sites are located on the catalyst surface at the same time and close to each other,which leads to a higher carrier recombination rate and a lower hydrogen production rate.Therefore,in order to avoid the disadvantages of powder catalytic particles,a film-like Ti/NaTaO₃:La was prepared on the Ti foil substrate.The thin film catalyst was convenient for recycling and reuse,greatly reduced environmental pollution,and generated hydrogen and oxygen on both sides of the film.In order to improve the efficiency of the film-shaped photocatalyst on the original basis,a composite Ti/TNT/N-P/NaTaO₃:La film photocatalyst composed of TiO₂ nanotube array/n-type TiO₂ nanoparticle film/NiO film/NaTaO₃:La particle film was formed,and the interface layer which were in direct contact with the N layer in the composite film material was optimized.The detailed inquiry process was described below:（1）Selecting Ta₂O₅,Na₂CO₃ and La₂O₃ as original reagents,powdered NaTaO₃:La samples were made by high-temperature solid-phase reaction.Then select Ti foil as the substrate to prepare Ti/NaTaO₃:La film-like catalyst by screen printing technology,and explore the effect of the difference in annealing temperature on the performance of film-like catalyst.In the photocracking water experimental reaction,300 W high pressure mercury lamp was selected as the illuminant,and experimental circumstances were NaOH alkaline solution and the pH value was equal to 13.The test results show that as the annealing temperature increases,the photolytic water activity of the Ti/NaTaO₃:La thin film photocatalyst increases first and then decreases.When the temperature was 400 ^oC,the amount of H₂ and O₂ generated reaches the maximum,reaching 156μmol/4 h,indicating that the temperature has effect on the efficiency of the thin film photocatalyst.（2）On the surface of Ti substrate,prepare TiO₂ nanotubes which as an electron transport layer（TNT）,a NiO layer is prepared thereon as a p-type material（P）.In order to increase the area of the heterojunction region directly formed by the combination of TiO₂ nanotubes and NiO films,the same anatase type TiO₂ layer was formed on its surface by dipping the titrasol gel as a n-type material（N）,and the p-n junction was formed with a large heterojunction region.Finally,the NaTaO₃:La photocatalyst layer was screen printed and annealed at 400°C to obtain the composite thin film Ti/TNT/N-P/NaTaO₃:La photocatalyst.In addition,the electron transport layer and n-type were explored separately.It shows that when the annealing condition is 450°C,the TiO₂ nanotubes formed are most conducive to the vertical transport of electrons;When four layers of TiO₂ thin films are formed,the surface is flat,uniform,dense and almost no holes exist,which is conducive to the close combination with the p-type layer to form a better quality p-n junction.At this time,the composite film Ti/TNT/N-P/NaTaO₃:La photocatalyst can produce up to 348μmol/4 h.In addition,compared with Ti/NaTaO₃:La photocatalyst,the composite Ti/TNT/N-P/NaTaO₃:La thin film photocatalyst is significantly better than the former.This is due to the built-in electric field generated by the p-n junction in the Ti/TNT/N-P/NaTaO₃:La thin film photocatalyst under light,which can enable more photo-generated electrons to be used for hydrogen production;Secondly,the thin film photocatalyst can produce hydrogen and oxygen on the different sides of the Ti foil,which overcomes some of the shortcomings of the traditional powder photocatalysts.This kind of photocatalyst will have a good application prospect in the efficient water splitting to produce hydrogen.