Synthesis And Photocatalytic Hydrogen Production Properties Of Fe-based Metal Organic Framework Derived Metal Sulfide And Phosphide

Metal-organic framework（MOFs）materials,also known as porous coordination polymers,are a class of porous crystalline materials with periodic multi-dimensional network structure formed by metal ions or metal clusters and organic ligands through self-assembly.MOFs generally have the advantages of regular structure,high porosity,high specific surface area,easy functionalization,etc.,which have potential applications in the field of catalysis.Meanwhile,MOFs can also be used as precursors to prepare a series of derivative materials.Derivatives with MOFs as templates often retain the structural characteristics of the original MOFs,so they can be used as excellent and stable heterogeneous catalysts,co-catalysts or catalyst carriers.Presently,the practical application of most Fe-MOFs in photocatalysis is limited due to their poor absorption performance in the visible light region,serious photogenerated carrier recombination and poor electrical conductivity,etc.In view of the above problems,Fe-MOFs can be directly derived into various inorganic catalysts.By using dyes as photosensitizers,we have successfully applied Fe-MOFs to construct a dye sensitization photocatalytic system for photocatalytic hydrogen evolution reaction（HER）.Specific research contents are as follows:Firstly,Ni:Fe₃S₄ nanorod catalyst was synthesized by doping Ni as a metal element into MIL-88B（Fe）precursor using solvothermal one-step sulfurization method.Eosin Y（EY）was used as a photosensitizer for photocatalytic HER in dye sensitization system under visible light irradiation.As a result,effectively utilizing of visible light at 500-600 nm and rapid transfer of the photogenerated electrons to Ni:Fe₃S₄ nanorods was achieved with significant photocatalytic HER performance.The superior photocatalytic performance can be attributed to the introduction of Ni ions,which effectively change the electronic structure on the surface of Fe₃S₄;and improve the conductivity and surface catalytic performance.Further,DFT calculations show that Ni doping can optimize the adsorption energy of S atom on the surface of Fe₃S₄nanorods to H atom.Therefore,Ni:Fe₃S₄ has relatively good adsorption/desorption ability,thus improving the photocatalytic reaction rate.Interestingly,the photocatalytic HER rate of the system is reached up to 3240μmol g^-1_cat h^-1 with an apparent quantum yield of 12%at 500 nm,which is better than that of Fe₃S₄ supported precious metal Pt for photocatalytic HER.Secondly,Pt-Fe₂P nanorod was prepared by introducing H₂Pt Cl₆ into the MOF channel with the help of double solvent using one-step calcination phosphating method.The as prepared Pt-Fe₂P nanorod was successfully applied for dye-sensitized photocatalytic HER system.It has been found that Pt can be closely embedded into Fe₂P,so that the contact between the two is closer,which facilitated the electron transfer.Thus,improving the photocatalytic HER performance.The result indicates that one-step phosphating method can effectively avoid the uneven deposition of Pt particles,interfacial ligand adsorption,and interfacial contact instability in common loading methods,thus enhancing the stability of the composite catalyst in the catalytic system.Furthermore,Fe/Ni-MOF and Fe/Co-MOF were also applied to explore the universality of this loading mode.The results indicate that Pt-embedded bimetallic phosphide nanorods under the condition of retaining the regular morphology of MOF can greatly improve the photocatalytic HER performance（about 7.5times）.The method of one-step synergistic derivation of composite catalysts provides a reference strategy for preparation of other composite catalytic materials for high efficient photocatalysis application.