ZIF-based Preparation Of Nickel-iron Hydrotalcite And Its Oxygen Evolution Reaction Performance

The oxygen evolution reaction(OER)is an important reaction in the process of energy conversion and storage.The improvement of the electrocatalytic performance of OER can significantly reduce the potential in the electrolyzed water reaction and improve the efficiency of conversion and storage of renewable energy.Although the noble metal oxides such as IrO2 and RuO2 can exhibit good electrocatalytic properties in OER,their limited resources and high price restrict their wide application.Therefore,the development of OER electrocatalysts with excellent performance,good stability and low price is an important goal in the field of oxygen evolution electrocatalysis.Among them,Layered double hydroxide(LDH)is considered to have great potential in OER due to its large specific surface areas and unique layered structure.However,LDH reported so far still have problems such as limitation on the number of active sites,poor conductivity and slow mass transfer kinetics.In order to solve these problems and further improve the catalytic activity of hydrotalcite in OER,two kinds of ZIF-induced NiFe-LDH were prepared and characterized by characterizations and OER performance.(1)Preparation of ZIF-67 induced NiFe-LDH porous nanosheets and its oxygen evolution performance,the NiFe-LDH nanosheets induced by ZIF-67(NiFe-LDH/ZIF-67)are prepared via a coupling method of a self-sacrificing template method and a co-precipitation method.Atomic force microscope(AFM)and field transmitance electron microscropy(TEM)analysis indicate that NiFe-LDH/ZIF-67 consist of thin porous nanosheets.X-ray photoelectron spectra(XPS)analysis shows that the binding energy of Ni2+ and Fe3+ of NiFe-LDH/ZIF-67 are lower than that of pristine NiFe-LDH,and contain more oxygen vacancies.The overpotential of NiFe-LDH/ZIF-67 for OER is 222 mV at 10 mA cm-2,lower than that of pristine NiFe-LDH,ZIF-67,and the commercial RuO2,indicating that its high electrocatalytic activity for OER.Compared with pristine NiFe-LDH,NiFe-LDH/ZIF-67 shows lower tafel slope,higher electrochemical active surface area,and higher electron transport ability.The high electrocatalytic performance of NiFe-LDH/ZIF-67 may be attributed to its thin porous nanosheet structure,which is derived from the structural influence of ZIF-67 and the coupling effect of a self-sacrificing template method and a co-precipitation method.(2)Preparation of ZIF-8 derived Ni-doped carbon-supported NiFe-LDH(NiFe-LDH/NC)and its oxygen evolution performance.Ni-doped carbon-supported NiFe-LDH derived from ZIF-8 was prepared by deposition sedimentation method.A series of characterizations showed that the catalyst had an extra large specific surface area and a layered structure different from the conventional NiFe-LDH.In addition,Ni-doped carbon(NC)could promote the formation of low-fold pyridine N at a higher pyrolysis temperature,thereby providing more N-defect sites and more efficient active sites and increasing activity.In OER,the overpotential of NiFe-LDH/NC was 249 mV at a current density of 10 mA cm-2,which was lower than that of conventional NiFe-LDH and commercial RuO2.At the same time,the catalyst had a lower Tafel slope and a higher electrochemically active area,as well as much less resistance than conventional NiFe-LDH.