Fe-Ni Based Metal-Organic-Frameworks Photocatalyst For Visible Light-Driven Water Oxidation

Metal-organic frameworks（MOFs）are a new class of porous coordination polymeric materials discovered in the 1990s.It is a fibrous porous structure,and the organic ligands support each other through metal ions as connection points to form the spatial 3D structure.It has many advantages such as high porosity,low density,regular pore channels,and large specific surface area.The spatial and energy band structures of MOFs can be effectively regulated by using different metal ions and organic ligands.The researchers can adjust the spatial structure of MOFs by changing the synthesis conditions of MOFs to adapt the different functional requirements.With the advancement of human science and technology,the demand for energy continues to increase.Fossil energy with limited content is difficult to meet the needs of human for long-term survival.People urgently need to find corresponding alternative energy sources.Solar energy is clean,green,and inexhaustible,how to convert radiated sunlight into storable energy has become a main challenge for the scientists.At present,the method of photocatalytic water splitting to convert solar energy into hydrogen energy through catalyst has received great attention.However,the current conversion efficiency of solar energy to hydrogen fuel has not yet met the requirements for large-scale applications.The mismatch between the electron and holes consumption at the hydrogen-and the oxygen-producing sites is one of the main reasons for the low conversion efficiency.The holes consumption rate at oxygen-producing site is usually far below electrons consumption rate at hydrogen-producing site,which causes the overall water splitting efficiency still cannot be improved.The oxygen generation by water oxidation involves a complex four-electron process,in which the formation of oxygen-oxygen bonds need high activation energy.Therefore,efficient photocatalytic oxygen generation catalysts are by far the biggest challenge in developing effective photocatalysts.In this paper,based on the structure of MIL-100 series MOFs,we used ferric chloride hexahydrate and nickel nitrate hexahydrate as metal resource,to synthesize iron-nickel MOFs materials with trimesic acid as ligands.The physicochemical property such as microstructure,atomic chemical environment and light adsorption were also characterized.After a series of photocatalytic efficiency tests,it is proved that bimetal Fe-Ni MOF has better photocatalytic oxygen evolution efficiency than single metal Fe MOF and Ni MOF.Secondly,taking advantage of the easy controllability in its structure,the photocatalytic performance of Fe-Ni MOF was further optimized by regulating the metal molar ratio,synthesis temperature and synthesis time during the synthesis,and finally the photocatalytic efficiency of Fe-Ni MOF was increased to 4.86 mmol h^-1g^-1.The material has extremely high photocatalytic oxygen evolution efficiency and good catalytic stability,which provides a new direction for the design of efficient photocatalytic oxygen evolution materials.