Preparation And Catalytic Properties Of Nickel Oxide Nanomaterials By Atomic Layer Deposition

Catalysts are widely used in energy,environment,industrial production and other fields.Activity and stability of catalysts are important for evaluating catalyst performance.Traditional preparation methods of catalyst include impregnation,hydrothermal,and sol-gel.However,the catalysts prepared by these methods have lower catalytic activity and shorter service life,which is mainly because the active components of the catalyst are not uniformly distributed on the carrier,and the amount of catalyst loaded and active components cannot be accurately controlled.In addition,during the preparation process of catalyst,high-temperature calcination is required,which often destroys the surface morphology of the support and further reduces the catalytic activity of the catalyst.Atomic layer deposition（ALD）is a technology for preparing ultra-thin films and ultra-fine nanoparticles at the atomic level,which can deposit ultra-thin films of one atomic layer at a time.ALD utilizes the self-limiting surface reaction between the gas-phase chemical precursor and the chemically active sites on the surface of the substrate to uniformly disperse the active components of the catalyst on the surface of the carrier.Also,the loading of the catalyst together with the amount and size of the metal nanoparticles can be accurately regulated by controlling the number of ALD deposition cycles.The technology also has a high degree of shape retention,step coverage and repeatability.Therefore,the application of ALD technology in the field of catalysis is worthy of in-depth study.This paper uses ALD technology to load NiO nanoparticles on Fe/Ni-MOFs materials to prepare NiO@Fe/Ni-MOFs composite materials,and explore its electrocatalytic activity and stability;NiO/TiO₂ nanomaterials were prepared by loading NiO nanopaticles on TiO₂.Then,their catalytic performance was explored.The specific work is as follows:（1）Preparation of NiO@Fe/Ni-MOFs composite material and its electrocatalytic performance.In this paper,Fe/Ni-MOFs was prepared by grafting Fe（hfac）₂TMEDA onto the surface of Ni-MOFs by acid-amine reaction.Then,by controlling the number of ALD cycles.NiO nanoparticles were deposited on Fe/Ni-MOFs to prepare NiO@Fe/Ni-MOFs nanocomposites,with 30,60 and 100 cycles.They were characterized by XRD,SEM,EDS and TEM.Finally,the electrochemical performance of the composite material has been tested.and results show that the deposition of NiO with 60 cycles on the surface of Fe/Ni-MOFs.NiO@Fe/Ni-MOFs composite with 60 cycles can be stable for more than 8 hours in alkaline electrolyte.（2）Preparation of NiO/TiO₂ composite material and its photocatalytic performance NiO/TiO₂ composites with different cycles were prepared by ALD.The photocatalytic degradation of phenol was used as a probe reaction to explore the catalytic performance of NiO/TiO₂ nanomaterials prepared by ALD method.The influence of other different factors on the catalytic performance of the catalyst was also explored,and compared with the catalyst prepared by the impregnation method.The research results showed that NiO/TiO₂ with 15cycles has the highest photocatalytic activity and good stability.After being exposed to ultraviolet light for 4 hours,the phenol degradation rate of the NiO/TiO₂ catalyst prepared by ALD method was 97.5%,while the phenol degradation rate of the NiO/TiO₂ catalyst prepared by the impregnation method was 86.8%.XRD,SEM,EDS,TEM,AAS,BET and H₂-TPD results showed,that the ALD method has successfully prepared NiO/TiO₂ nanomaterials.Among the NiO/TiO₂ nanomaterials prepared by ALD,NiO is more uniformly distributed on the carrier and specific surface area of catalyst is larger.What’s more,the surface morphology of the carrier didn’t change by ALD method.