Synthesis And Electrochemical Properties Of Metal-organic Framework Derived Fe-based Materials For Oxygen Evolution Reaction

Hydrogen is an ideal renewable energy due to its abundant resources,high efficiency,high energy density,and environmental friendliness.As known,water splitting is one of the most effective ways to obtain hydrogen energy.However,the oxygen evolution reaction?OER?process involves the transfer of four electrons and the generation of multiple intermediates,which greatly affect the efficiency of water splitting.Therefore,it is necessary to develop efficient electrocatalysts to reduce OER overpotential.Transition metal Fe is one of the promising electrocatalytic materials for water splitting with earth abundant and less toxic.The reported pure Fe-based materials still have the disadvantages of low conductivity and poor stability hinder their widespread commercial applications.An effective way to improve the catalytic performance of Fe-based materials is to introduce conductive materials and elemental doping,which can significantly increase the number of active sites and charge transfer rate of the catalyst.Metal organic framework?MOF?is a porous material with periodic network structure formed by metal ions and organic ligands through coordination bonds.It not only has a large variety,large specific surface area,and high porosity,but also has a rich metal center.Therefore,it is particularly important to use simple synthesis method to prepare Fe-based MOFs materials that are environmentally friendly,reasonable in structure,good in conductivity,and high in active sites.In this paper,a series of Fe-based MOFs catalysts are synthesized by using simple solution immersion method and solvothermal method.We systematically studied the relationship between the composition,structure,morphology of materials and the catalytic performance of water splitting.The main researches are as follows:?1?we report the in-situ development of Fe?TCNQ?₂ nanowires array on Fe foil via a solution immersion method in 7 mM TCNQ solution at 60°C for 4 h.The effects of electrical double-layer capacitor and conductivity in the electrochemical OER performance of Fe?TCNQ?₂/Fe were investigated.As a 3D OER catalyst,Fe?TCNQ?₂/Fe drives a geometrical catalytic current density of 10 mA cm^–2 at overpotential of 340 mV in 1.0 M KOH under optimal conditions.It also shows strong long-term electrochemical durability with its catalytic activity being retained for at least 110 h.?2?Based on study 1,we report an evident improvement of OER activity by incorporating Fe and Co into MOFs nanosheet array supported on nickel foam?MIL-53?Co-Fe?/NF?.Compared with the MIL-53?Co?/NF?348 mV?and MIL-53?Fe?/NF?380 mV?,MIL-53?Co-Fe?/NF exhibits improved OER activity with ultralow overpotential of 262 mV to afford 100 mA cm^–2 current density,revealing that co-doped Fe and Co into MOFs could further boost the intrinsic OER activity of MOFs due to the synergistic effect.Additionally,this catalyst also displays outstanding long-term electrochemical durability for at least 80 h?3?Based on study 1,we reported that MIL-53?Tb-Fe?/NF was prepared by co-doping Fe and lanthanide metals Tb with higher coordination numbers to improve the OER performance of single metal organic frameworks via one step solvothermal method.As prepared MIL-53?Tb-Fe?/NF drives a geometrical catalytic current density of 100 mA cm^-2 only need 241 mV overpotential,which proves that Tb and Fe co-doping effectively improves the catalyst activity.In addition,MIL-53?Tb-Fe?/NF has excellent electrochemical stability,its catalytic activity can be maintained for at least 25 hours.This work provides more insight into rare earth metal co-doping Bimetal-MOF as a highly active OER electrode material and opens up new strategies for developing promising highefficiency electrocatalysts in practical applications...