Study On Preparation And Performance Of The H₂O₂ Electroreduction Composite Cathodes

H₂O₂-based fuel cells with many advantages of high electrochemical activity,high energy density,easy storage and transportation,and easy operation,which have been widely used in special environments?underwater or in space?where oxygen is thin.The study of high-activity,high-stability composite electrodes is beneficial to improve the performance of H₂O₂-based fuel cells.In this paper,Co-CoC/NF,Pd@SnO₂/CP and Pd@rGO/CP composite electrodes were synthesized using nickel foam and carbon paper as substrates,and their phases compositions and morphologies were characterized by XRD,SEM,EDS,and XPS.Cyclic voltammetry,linear voltammetry and chronoamperometry were used to study the catalytic performance of the composite electrode for H₂O₂ electroreduction.The performance of the metal?Al or Mg?-H202 semi-fuel cell was tested using A1 or Mg alloy as the anode and the prepared electrode as the cathode.The results are as follows:Co-CoC/NF composite electrode was prepared by using high temperature annealing method with Ni foam as the substrate.During the preparation,the amount of Co-CoC deposited on the surface of nickel foam increased with the concentration of cobalt nitrate solution increasing.When the concentration is 0.25 mol/L,the cobalt carbide nanoparticles were spherical,connected into a hollow rod-like structure,and grow uniformly on the surface of the nickel foam substrate like a chrysanthemum.In 3 mol/L NaOH+0.5 mol/L H₂O₂ solutions,the reduction current density of Co-CoC/NF electrode for H₂O₂ reduction reached 423 mA/cm2 at E=-0.5 V.The Al-H₂O₂ semi-fuel cell with Co-CoC/NF as the cathode and Al alloy as the anode showed a maximum power density of reaches 360 mW/cm2 when the current density is 398.26 mA/cm2 and the battery voltage is 1.36 V at 50?.And the cell voltage retained stable at about 1.4 V during a constant discharge of 50 h.With carbon paper as the substrate,SnO₂/CP and rGO/CP composites were prepared using hydrothermal and chemical reduction methods,respectively.Pd nanoparticles were electrodeposited on the two composites by a constant voltage method to synthesize Pd@SnO₂/CP and Pd@rGO/CP electrode.During the preparation process,the load of SnO₂ on the surface of carbon paper decreased with increasing the holding time of precursor solution.When the resting time is 20 min,the SnO₂ nanorods grow uniformly on the surface of carbon paper with a diameter of about 45 nm.Pd nanoparticles loaded between SnO₂ nanorods with a spherical-like shape.In 0.5 mol/L H₂O₂+3 mol/L H2SO4 solutions,the reduction current density of Pd@SnO₂/CP reached 231.5 mA/cm2 at E=0 V.With Pd@SnO₂/CP as the cathode and Mg alloy as the anode,the maximum power density of the Mg-H₂O₂ semi-fuel cell reaches 192.39 mW/cm2 when the current density is 248.03 mA/cm2 and the cell voltage is 0.77 V at 60?.And during a constant discharge of 50 h,the cell voltage is stable above 2.0 V.The load of rGO on carbon paper increased with the concentration of graphene oxide increasing.And rGO coated on the surface of carbon paper with wrinkle when the concentration of graphene oxide is 1.5 mg/mL.Pd nanoparticles on the rGO/CP substrate are spherical with an average particle size of 9-13 nm.In 0.5 mol/L H₂O₂+3 mol/L H2SO4 solutions,the reduction current density of Pd@rGO/CP reached 298.5 mA/cm2 at E=0 V.With Pd@rGO/CP as the cathode and Mg alloy as the anode,the maximum power density reaches 217.7 mW/cm2 when the current density is 348.4 mA/cm2 and the cell voltage is 0.61 V at 65?.And the cell voltage stabilized above 2.1 V after a constant discharge of 50 h.