Synthesis Of Single-atom Supported Ti O₂catalyst And Study On Photolysis Of Water For Hydrogen Production

Among the many photocatalysts,TiO₂ has the outstanding characteristics of simple preparation process,low cost,no secondary pollution,no toxicity and recyclability,which has become a research hotspot in the field of photocatalysis.However,it only responds to ultraviolet light in sunlight because the quantum efficiency is low,and the photogenerated electrons and holes are easily recombined and annihilated rapidly.Therefore,it is necessary to improve the catalytic activity and catalytic efficiency of photocatalytic materials by regulating the bulk phase,microstructure,and interfacial chemical composition,and single-atom loading is an important way to achieve this goal.The so-called single-atom supported catalysts（SACs）are composite catalysts modified by dispersing metal modifiers on a semiconductor substrate in the form of single atoms.On the one hand,single-atom loading can improve the catalytic performance of the substrate material,and on the other hand,the catalytic utilization rate of metal atoms in the catalytic process can be greatly improved,even up to 100%.Based on the synthesis of single-atom modified TiO₂ photocatalysts,this work systematically studies the effect of single-atom loading on the photocatalytic performance of TiO₂.The details are as follows:（1）Synthesis and photocatalytic properties of TiO₂ photocatalysts with different morphologies:The structure and morphology of TiO₂ nanophotocatalysts have a great influence on the catalytic process,and the large specific surface area and volume reduction will affect the crystallinity and defects of the catalyst.Properties such as concentration and grain boundary density not only affect the separation of electrons and holes,but also affect the migration of electrons.Therefore,tubular,sheet,spherical,hollow sphere and flower-like TiO₂ catalysts were synthesized by five methods,respectively,and the corresponding characterizations were carried out.Then,the relationship between morphology and catalytic activity was explored by using the difference in photocatalytic water splitting performance for hydrogen production.The results show that the properties and hydrogen production activity of flake TiO₂ are better than other morphologies,so flake TiO₂ is used as the substrate material for subsequent metal single-atom modification.（2）Synthesis of Pt/Pd single-atom modified TiO₂ nanosheets and research on their photo-splitting properties:After screening in the first part,the substrate material was determined.Then,according to the method in the literature,defects,namely oxygen vacancies,are first introduced into the nanosheets,and then noble metal single atoms are introduced and anchored to these vacancies.After a series of characterizations,the existence of single atoms of noble metals has been verified.However,not all noble metals exist in the form of single atoms,and some of them exist in the form of clusters.Finally,the photocatalytic hydrogen production performance evaluation also gave satisfactory results.（3）Synthesis of Pt/Pd bimetallic single-atom modified TiO₂ nanosheets and its photolysis performance:On the basis of single-metal modification,the synthesis of bimetallic single-atom modified TiO₂ nanosheet catalysts was carried out.The effect of the coexistence of two noble metal atoms on catalyst performance was investigated.And compared with the bimetallic cluster supported catalyst,a series of results characterization and performance evaluation results show that the effect of single-atom modification is better than that of clusters.（4）The relevant theoretical calculations were carried out on the bimetallic single-atom modified TiO₂ catalyst by VASP software,and the DOS,differential charge density and energy band structure of the relevant catalyst structure were obtained.The calculation results and the experimental results confirmed each other.The design and future industrial application of supported TiO₂ photocatalysts provide useful reference.