Synthesis And Electrocatalytic Study Of POM@MIL-101 Derived Composites Nanomaterials

Metal organic frameworks（MOFs）are a kind of crystalline materials with large specific surface area,high porosity and diverse functions,which are bridged by coordination atoms from organic ligands and metal ions.In recent years,MOF materials are still the direction of most researchs.Basically,they are used as precursors to hybridize with polyoxometalate,graphene and carbon nanotubes to generate electrocatalysts after calcination at high temperature or phosphoryation.High temperature annealingcomposite materials can not only increase the porosity,but also form more active sites,thus improving the electron transmission rates and reducing the kinetic reaction conditions in the process of electrocatalysis.Herein,polyoxometalate compounds were packed into the channels of MOF materials through in-situ synthesis to form POM-based composites,which were characterized by IR,thermogravimetry,XRD and scanning electron microscopy.We also investigate the electrochemical properties of the composites.1.Firstly,the Keggin-type polyoxometalate compound H₃PMo₁₂O₄₀ and MIL-101 were combined to form composite material POM@MIL-101 by the solvothermal method.The composite was immersed in cobalt nitrate solution,nickel nitrate solution and cobalt-calcium mixturesolutiontoformPOM@MIL-101（Co）,POM@MIL-101（Ni）and POM@MIL-101（Co/Ca）,with subsequent formation of a series of porous nanomaterials.Electrochemical testing indicates that POM@MIL-101（Co/Ca）-800 has the best OER performance.In addition,We use NaH₂PO₂ to phosphate POM@MIL-101（Co/Ca）at different timeandgotphosphatizedsamplesP-POM@MIL-101（Co/Ca）-800-3h,P-POM@MIL-101（Co/Ca）-800-4h and P-POM@MIL-101（Co/Ca）-800-5h.After phosphation for5hours,P-POM@MIL-101（Co/Ca）-600-5h,P-POM@MIL-101（Co/Ca）-700-5h,P-POM@MIL-101（Co/Ca）-800-5h are obtained by changing phosphating temperatures.Electrochemical testing indicates that P-POM@MIL-101（Co/Ca）-800-5h has the best OER performance,with an initial potential of 320 mV and an overpotential of 470 mV when the current density is set to be10 mA cm^-2.2.The Co-based polyoxometalate TBA₅H₁₀{CoSb₆O₄（H2O）₃[Co（hmta）SbW₈O₃₁]₃}·28H₂O was successfully loaded into the channel of MIL-101 and then phosphated treat ment at 800℃.Electrochemical test results show that P-TBA-Co-Sb₉W₂₁@MIL-101-800-5h has a starting potential of 540 mV and also an oxygen reduction potential of 0.72 V.