The Preparation Of ZnIn₂S₄ Supported Noble Metal Photocatalysts And Their Performance In The Selective Oxidation Of Aromatic Alcohols

Indium zinc sulfide?ZnIn₂S₄?is a ternary metal sulfide.Because its unique optical properties,good chemical stability and suitable energy band structure,it has become one of the typical visible light-responsive photocatalysts in ternary sulfides.However,it has the problems of fast photogenerated electron-hole recombination and low photon utilization,which affects the photocatalytic efficiency and its application in the field of organic selective oxidation.In view of the above problems of ZnIn₂S₄ materials,the use of precious metal deposition to construct metal/semiconductor systems or morphology control is one of the effective ways to promote the carrier separation of ZnIn₂S₄ photocatalysts because of the multi-component synergy between metals and between metals and semiconductors Function,can reduce the degree of semiconductor photo-generated electron-hole recombination,these advantages will help enhance the photocatalytic activity.A one-step solvothermal method was used to synthesize the indium zinc sulfide material,and the NaBH₄ reduction method was used to successfully load Au and Pd on the surface of the daisy-shaped ZnIn₂S₄ microspheres to prepare Au/ZnIn₂S₄ and Pd/ZnIn₂S₄photocatalysts.UV-vis-DRS,PL,XPS,photoelectrochemical tests were carried out on the composite materials.Due to the existence of the Mott-Schottky effect between metal-semiconductor,the transfer of hot electrons from metal to semiconductor was realized,and the efficiency of photo-generated carrier separation was found to be improved.The catalytic selective oxidation conversion rate reached 43.1%,which was 6%higher than the photocatalytic efficiency of ZnIn₂S₄.Since the metal particles and the carrier are not independent systems,excited hot electrons are likely to cause plasmon resonance effect?LSPR?and interfacial synergy between metals.Therefore,this experiment laid the foundation for the next step to build a bimetal/semiconductor.First,a one-step solvothermal method was used to synthesize the photocatalyst,and then Au-Pd with different molar ratios was reduced to the surface of the chrysanthemum ZnIn₂S₄ microsphere photocatalyst to explore the optimal metal ratio and metal content,and extend the optimal catalyst to aromatic alcohol Selective oxidation research.Through a series of photoelectric performance characterization,Au-Pd/ZnIn₂S₄ was found to have a longer carrier lifetime and a higher photogenerated electron-hole migration rate.Among them,the 0.5 wt%Au-Pd/ZnIn₂S₄ photocatalyst showed the highest photocatalytic activity,and the conversion rate to aromatic alcohol was increased to 90%,which was 1.5,2.0 and1.3 times of ZnIn₂S₄,Au/ZnIn₂S₄,Pd/ZnIn₂S₄,respectively.The combination of capture experiment and ESR technique found that the effect of h⁺,·O₂^-and carbon center radicals on the photocatalytic selective oxidation on Au-Pd/ZnIn₂S₄.The bimetallic/ZnIn₂S₄composite structure confirms that the construction of a bimetallic interface cooperative photocatalyst is an effective strategy for developing high-performance photocatalysts.A simple mixed solvent thermal method is used to adjust the morphology of ZnIn₂S₄to improve its visible light utilization.In the third system,ZnIn₂S₄ microspheres with different crystal plane exposures were obtained by adjusting the volume ratio of hydroalcohol.The initial exploration of the photocatalytic efficiency of benzyl alcohol was increased to 64%,and the existence of S vacancies was found,which laid the foundation for the subsequent exploration of the relationship between the crystal structure and photocatalytic performance.In short,the construction of semiconductor/noble metal systems and the crystal plane control of ZnIn₂S₄ have promoted the ability of semiconductors to absorb visible light to varying degrees,improved the efficiency of photogenerated carrier transfer and separation,and made the photocatalyst exhibit excellent photocatalytic selective oxidation performance.It is of great significance in the field of solar-driven organic synthesis.