Synthesis Of Metal Organic Frameworks(MOF) For Electrocatalytic Water Splitting

Electrocatalytic water splitting is an energy storage and conversion technology which concludes hydrogen evolution reaction（HER）and oxygen evolution reaction（OER）.OER is the key step which involves a transfer process of four electrons and four protons.Metal organic frameworks（MOF）have been widely studyed due to their high specific surface area and unrivalled degree of tunability.However,the low conductivity of MOF obstructs electrons to be transferred to the active center.In this study,a self-supporting nano-sheet-shaped ferrocene-based MOF was designed and synthesized for electrocatalytic OER.The catalytic mechanism was investigated by in-situ electrochemical Raman and density functional theory calculations（DFT）;By incorporating a third metal to control the metal active site,the HER catalytic activity of the ferrocene-based MOF is significantly improved.（1）NiFc-MOF was prepared on nickel foam（NF）by a solvothermal method using nickel chloride hexahydrate and 1,1′-ferrocenedicarboxylic acid.At the same time,the nickel-iron layered double hydroxide（Ni Fe LDH/NF）was synthesized as reference material.In 1 M KOH aqueous,the overpotential of NiFc-MOF/NF at 10 m A·cm^-2 is 195 m V;at 100 m A·cm^-2 the overpotential is 241 m V,which is 50 m V lower than Ni Fe LDH.The stability test showed that the activity of NiFc-MOF/NF was stable within 40 hours.In-situ electrochemical Raman test and density functional theory calculations show that NiFc-MOF/NF the active site is Ni atom during the OER catalytic process.The ferrocene group enhances the electron transport capability and the unique electronic 2D structure promotes the contact between the nickel active sites and hydroxide radical intermediates so that the theoretical overpotential of NiFc-MOF is only 0.52 e V,which is lower than the theoretical value of 0.81 e V for Ni Fe LDH.（2）By integrating NiFc-MOF with trace amounts of Ru species（Ni/Fe/Rh=1:1:0.03）,the Ni active center was successfully adjusted,which greatly accelerated the slow alkaline HER kinetics of NiFc-MOF.In 1M KOH,the overpotential of Ru_0.03@NiFc-MOF/NF at 10m A·cm^-2 is-75 m V lower than NiFc-MOF by 150 m V,which is due to the strong interaction between the Ru and Ni.In addition,alkaline HER stability of Ru_0.03@NiFc-MOF/NF up to 90h.