Preparation And Photocatalytic Water Splitting Properties Of The Thin Film Photocatalysts Of NaTaO₃:La

Severe energy shortages and environmental pollution problems are currently facing tremendous human challenges.Therefore,the development of clean,pollution-free energy is not only enough to fill the shortage of energy but also avoid the environmental pollution caused by the burning of fossil fuels.As a result,hydrogen can enter the people's field of vision as a clean,pollution-free secondary clean energy source.Among these,photocatalytic water-based hydrogen production,which uses solar energy as a driving force to decompose water into hydrogen and oxygen,has become a research hotspot.In recent decades,with continuous research and exploration of semiconductor photocatalytic water catalysts,NaTaO₃:La semiconductor powder photocatalysts have received extensive attention due to their high photocatalytic activity in full water dissolution and their stability in the catalytic process.However,the powder photocatalyst has the following shortcomings:First,the powder photocatalyst needs to be dispersed in water during the photolysis of water,which leads to its disadv-antageous recycling and reuse.Second,the powder catalyst is excited by light to generate photoelectron-hole pairs,and redox reaction occurs on the surface of the powder photocatalyst to generate H₂ and O₂.The resulting H₂ and O₂ are mixed together and difficult to separate.At the same time,the new H₂ and O₂ on the surface of the powder photocatalyst are too easy to recombine to form water,which affects the photolytic water activity of the powder photocatalyst.Third,the recombination of photo-generated carriers is the most important problem that hampers the efficiency of photolysis of water.Therefore,these disadvantages restrict the photolytic water activity of the powder photocatalyst and its commercial application.In view of the deficiencies of the above-mentioned powder photocatalyst,and with the aim of improving the photolytic water activity of the powder photocatalyst,the powder photocatalyst was modified.Firstly,NiO cocatalyst was prepared on NaTaO₃:La by impregnation method,and then Ti-based photocatalyst of Ti/NaTaO₃:La?NiO?thin film was prepared by screen printing technique,and its photolysis water activity was explored.The thin-film photocatalyst effectively solves the problem of non-recyclable use of powder samples and avoids the pollution of water resources.It is worth noting that the formation of H₂ and O₂ on both sides of the Ti foil was observed during the reaction.Then,in order to further promote the transfer of photoelectrons toward the back of the Ti foil,the formation of H₂ and O₂ on both sides of the thin film is better achieved,the surface reverse reaction is suppressed,and the photolytic water activity is improved.We introduce a p-n junction in a thin film photocatalyst and sinter it with Ti/NaTaO₃:La?NiO?to form a photocell-photocatalyst-combined structure,resulting in a Ti/TNT/N-P/Na-TaO₃:La?NiO?thin film.catalyst of light.In the case of light,the photocell can provide a certain bias for the photocatalyst,and promote the flow of photogenerated electrons to the back of the Ti foil.The reduction reaction produces H₂,and the vacancies remain on the surface of the powder sample to generate an O₂ oxidation reaction to achieve H₂ and O₂ in the Ti.The formation of the two sides of the foil effectively inhibits the surface reverse reaction,promotes the separation and transfer of photoelectron holes,and increases the photolysis water activity.The specific research content is as follows:?1?Using Ta₂O₅,Na₂CO₃ and La₂O₃ as reaction raw materials,NaTaO₃:La powder photocatalyst was prepared by solid-state reaction,NiO cocatalyst with different mass ratio was prepared by impregnation method,and then screen printing technology was used with Ti foil as base.A Ti/NaTaO₃:La?NiO?thin film pho-tocatalyst was prepared and its photolytic water activity was explored.In the photolysis water test process,the light source was a 400 W high-pressure mercury lamp and the reaction solution was a NaOH aqueous solution with pH=11.The test results showed that the photocatalytic water of the Ti/NaTaO₃:La?NiO?thin film photocatalyst was loaded with different mass ratios of NiO.The activity increases first and then decreases.When the mass ratio of NiO loading is 0.2 wt%,the gas generation rate is the highest,reaching 12.97?mol/h�cm².It is 2.32 times that of Ti/NaTaO₃:La thin film photocatalyst without NiO loading.?2?TiO₂ nanotubes,which are conducive to the longitudinal transmission of electrons,were prepared by anodization on Ti foils as an electron conduction layer?TNT?.In order to avoid the TiO₂ nanotube array directly bonding with the p-type NiO thin film to form a smaller heterojunction area,an n-type TiO₂ nanocrystalline thin film was prepared by a dipping method with sol-gel as a precursor.Finally,a p-type NiO thin film was prepared by spin coating on the n-type layer,and a TiO₂/NiO composite layer with p-n junction characteristics was obtained.Using it as a substrate,NaTaO₃:La?NiO?was combined with a screen printing technique to obtain a Ti/TNT/N-P/NaTaO₃:La?Ni O?thin film photocatalyst in which a photovoltaic cell and a photocatalyst were combined.The TNT and pn junctions?TiO₂/NiO?were explored.It was found that the crystallinity of the TiO₂ nanotubes under the 20 V reaction voltage is best,and the nanotubes grow vertically.These characteristics indicate that they are conducive to the longitudinal transport of electrons;the prepared n-type The surface of the layer and the p-type layer are both flat and dense,and the heterojunction formed is tightly bounded.There are almost no holes between the interfaces.Under light,the p-n junction can provide a certain bias for NaTaO₃:La?NiO?.Finally,analyzing the photolysis water test results shows that the photolytic water activity of Ti/TNT/N-P/NaTaO₃:La?Ni O?thin film samples is generally higher than that of Ti/NaTaO₃:La?NiO?thin film samples.In addition,the photocatalytic water gas generation rate of Ti/TNT/N-P/NaTaO₃:La?NiO?thin film samples with different NiO spin coating numbers was found to be optimal when spin coating four layers,reaching 29.27?mol/h�cm².It is 2.26 times higher than the gas generation rate under the optimum conditions of the p-n junction Ti/NaTa-O₃:La?NiO?thin film sample.In addition,hydrogen gas and oxygen gas are more efficiently produced on the positive and negative sides of the Ti substrate.Preliminary solutions to the inherent deficiencies of traditional powder photo-catalysts.