Synthesis Of Metal-organic Framework Derived Electrocatalyst And Their Catalytic Performance For Oxygen Reduction And Oxygen Evolution Reactions

The metal-air batteries have high hopes in the field of new energy applications and they have become a hotspot in the research of the new and efficient energy storage and conversion technology system for their advantages such as high theoretical energy density,smooth discharge voltage,safety,environmental protection,long life and low cost.Oxygen evolution reaction(OER)and oxygen reduction(ORR)are two core reactions in the metal-air battery charge and discharge process,but their slow response to the dynamics result in a higher overdrive in charge and discharge process which will cause high energy consumption.So the development of low-priced and effective bifunctional catalysts for OER and ORR is critical to the commercialization of metal-air batteries.Metal-organic framework(MOFs)especially MOFs containing Co,Cu and other transition metals derived composite catalyst have shown excellent OER/ORR catalytic properties.In this paper,a series of Co/Co3O4@NCN and Co-Cu/CN-n composite catalysts were prepared on the basis of ZIF-67 and HKUST respectively.Then,the structural information was explored by XRD,XPS,Raman and N2-adsorption and desorption and electrochemical tests were carried out in 0.1 M KOH solution to study thier OER and ORR catalytic performance.Co/Co3O4@NCN-600 exhibited the best bifunctional catalytic activity for OER and ORR in the Co/Co3O4@NCN series of samples,and the potential at the 10 mA·cm-2 current density during the catalytic OER process is 0.696 V,and the current density is as high as 32.929 mA·cm-2 at the potential of 0.8V in OER process;Notablely,Co/Co3O4@NCN-600 have a high catalytic activity for ORR which compare favourably with the commercial 20 wt.%Pt/C catalyst,and its half-wave potential and Tafel slope values were-0.138 V and 55.9 mV·dec-1,respectively,corresponding to the half-wave potential(-0.134 V)and the Tafel slope(63.4 mV·dec-1)of commercial 20 wt.%Pt/C.Co-Cu/CN-1.5 showed the best bifunctional catalytic activity for OER and ORR in the Co-Cu/CN-n series of samples,and the potential at the 10 mA·cm-2 current density during the catalytic OER process is 0.722 V,and the current density is as high as 29.582 mA·cm-2 at the potential of 0.8 V in OER process;Furthermore,its half-wave potential and Tafel slope values were-0.146 V and 48.7 mV·dec-1 in ORR process,implying a good dynamic performance.