| In the face of worldwide environmental pollution and energy shortages,it has become the focus of people’s attention to find and utilize green energy to ensure sustainable social development and sustained economic growth.With the development of photocatalytic technology,the effective utilization of solar energy provides new ideas for solving environmental energy problems.However,traditional photocatalysts have problems such as low utilization of sunlight and recombination of electron-hole pairs.Therefore,the development of new photocatalysts with full spectrum utilization and efficient separation of photogenerated carriers is the key to the development of photocatalytic technology.Compared with bulk materials,two-dimensional（2D）nanosheet materials with atomic thickness have attracted much attention due to their advantages such as larger specific surface area,extremely short photo-generated carrier transport distance,and easily tunable surface properties.Herein,titanium/niobium-based 2D nanosheets with ultrathin structure have been prepared by high-temperature solid-phase,proton exchange and intercalation exfoliation combined with pickling.On this basis,a metal catalysis method is adopted to controllably introduce defects at low temperature and mild conditions without external reducing agents,which construct a 2D nanosheet/metal heterojunctio,and obtain high-efficiency 2D nanosheets with broad spectral absorption.The properties of the prepared materials were characterized by photothermal synergistic catalytic oxidation of aromatic alcohols,and the catalyst materials with optimal photothermal synergistic catalytic performance were screened.The physicochemical properties of the samples were characterized and analyzed by electron paramagnetic resonance spectroscopy（EPR）,X-ray photoelectron spectroscopy（XPS）,and in situ infrared spectroscopy to explore the reaction mechanism of aromatic alcohols on the catalyst surface.1.The research proves that by loading Pd nanoparticles on titanate nanosheets（H2Ti6O13）and using photocatalysis,the regulation of oxygen defects and Lewis acid sites on the surface of nanosheets can be realized without destroying the original nanosheet structure.On the one hand,the appearance of oxygen vacancies expands the light absorption range of nanosheets,achieving nearly 90%absorption of visible light.On the other hand,the abundant Lewis acid sites on the surface provided a large number of reactive sites,which facilitated the adsorption and activation of aromatic alcohols.The aerobic oxidation of benzyl alcohol to benzaldehyde is used as a probe,and the Pd/H2Ti6O13 composites show superior photothermal synergistic catalytic performance,with the benzaldehyde production rate of 3520.5μmol g-1 h-1,which is 288%higher than that of the original nanosheets.At the same time,the active species generated by the reaction of aromatic alcohols on their surfaces were further explored through the characterization of radical quenching experiments and EPR active radical tests,thereby proposing the possible aerobic oxidation reaction mechanism.2.Pt nanoparticles were supported on titanate/niobate nanosheets to construct Pt/H2Ti6O13,Pt/HNb3O8 composites.It is found that Pt can introduce oxygen defects on the surface of nanosheets under photocatalysis.Moreover,by adjusting the photocatalytic time and the amount of Pt metal precursor,the controllable preparation of oxygen defects on the surface of nanosheets can be achieved.The Pt/HNb3O8 composite was selected as the research object to deeply study the effect of oxygen defects on the physicochemical properties and photothermal properties of nanosheets.The results show that,while maintaining the original nanosheet structure,the introduction of oxygen defects on the surface of niobate nanosheets expands its light absorption performance and achieves about 70%visible light absorption,which provides the basis for efficient conversion of solar energy for photothermal catalysis.The photothermal synergistic catalytic performance of the Pt/HNb3O8 composite catalyst was studied by using the anaerobic oxidation of benzyl alcohol to benzaldehyde coupled hydrogen production as a probe reaction.The results show that the optimal catalyst material exhibits a benzaldehyde production rate of 2032.1μmol g-1 h-1 and a hydrogen evolution rate of 1953.2μmol g-1h-1.Compared with the photocatalytic performance,the photothermal synergistic catalytic performance of Pt/HNb3O8 is improved by nearly 100%.Simultaneously,the role and changes of active species in the catalytic reaction system were studied by quenching experiments and EPR active radical determination,so as to propose the possible photothermal synergistic catalytic reaction mechanism.In conclusion,in this paper,the introduction of oxygen defect structure under low temperature and mild conditions was realized by metal catalysis,and the photothermal synergistic catalyst of titanium/niobium-based 2D nanosheets/metal heterojunction were successfully constructed.These catalysts realize the broad spectral absorption of nanosheets and improve the utilization of sunlight,which is of great significance for the future exploration of photothermal synergistic catalytic organic synthesis,clean energy preparation and other fields. |
