Preparation Of Co-MOF Electrode Materials And Their Catalytic Performance In The Hydrogen Peroxide

Direct peroxide-peroxide fuel cell（DPPFC）is a clean and efficient energy conversion device.H₂O₂ is directly used as battery fuel and oxidant,which has high energy density,non-toxic and easy to be transported.Therefore,DPPFC has become one of the most promising power generation technologies.In this paper,H₂O₂electrochemical catalytic electrodes on the base of Ni foam and using ZIF-67 as a template for its excellent skeleton structure to effectively increase the specific surface area and active material loading of the material,which supported the low-cost and abundant transition metal—Co as the main material for electrode modification.It was developed with in-situ impregnation,high-temperature calcination,etc.,which has good catalytic activity,high stability and suitable structure.The Co₃O₄@C/NF electrode was prepared by simple in-situ impregnation and high-temperature calcination as the electrode material for catalyzing the electroreduction of H₂O₂.Then,the Co₃O₄@C/NF was partially reduced by NaBH₄ with a concentration of 0.1 mol·dm^-3to obtain a Co-Co₃O₄@C/NF electrode,which was used as an electrode material for catalyzing the electrooxidation of H₂O₂.The element composition and morphology structure of the prepared electrode were characterized by SEM,XRD and other means.The electrochemical characteristics of the electrodes were compared and explored in a three-electrode system by cyclic voltammetry（CV）and chronoamperometry（CA）.The Co-Co₃O₄@C/NF electrode has a three-dimensional porous structure and ZIF-67retains the basic framework of MOF after calcination.ZIF-67 presents a network structure covering the surface of the foamed nickel substrate uniformly and Co-Co₃O₄ grows cylindrically on the calcined C framework.The oxidation current density under an applied potential of 0.5 V reaches 692 mA·cm^-2 in an electrolyte with H₂O₂ concentration of 0.4mol·dm^-3 and NaOH concentration of 2.0 mol·dm^-3,which is higher than the previously reported Co@Graphite/Paper electrode.When the H₂O₂ concentration is 0.6 mol·dm^-3 and other test conditions remain unchanged,the oxidation current density at 0.5 V is as high as 966mA·cm^-2.When the electrolyte composition is unchanged and the applied potential is 0.2 V,the oxidation current density is stable at 275 mA·cm^-2 with no significant attenuation occurs after1200 s chronocurrent test.According to Arrhenius equation,the activation energy of the reaction is 9.993 kJ·mol^-1.The electrode material has stable structure and good catalytic stability to H₂O₂.The Co₃O₄@C/NF electrode has a 3D porous structure.Co₃O₄ with a porous coral is uniformly distributed on the surface of the foam nickel and arranged tightly.A layered structure appears on the coral surface,which greatly increases the specific surface area of the electrode.When the electrode has a NaOH concentration of 2.0 mol·dm^-3 and H₂O₂ concentration of 1.2mol·dm^-3,the reduction current density reaches 737 mA·cm^-2 at a potential of-0.8 V.Under the same electrolyte composition,when the applied potential is-0.4 V,the reduction current density is stable at 175 mA·cm^-2 after 1800 s of chronocurrent test with no obvious attenuation.The activation energy of the electrode-catalyzed H₂O₂ reduction reaction calculated by Arrhenius equation is 16.6 kJ·mol^-1.