Preparation And Electrochemical Properties Of Catalyst Based On FeCo For Bifunctional Air Electrode

Investigation was carried out to synthesize Fe/C, Co/C and FeCo/C material by microwave heating reduction method for their application as catalysts for oxygen reduction (OR) and oxygen evolution (OE) in alkaline media.At first, we studied the influence of heating treatment, acid treatment and microwaving carbon material to ORR and OER as a support materiel. The results showed that the carbon witch heated by muffle at600℃for3hours was very stable when discharged in6M KOH at80mA/cm2after dipped in6M KOH for1day. The discharge voltage was0.87V. Though the carbon dipped in acid for7days had a higher ORR performance, the discharge voltage was only0.78V at the same conditions. As the stability was more important to bifunctional air electrode, we used the heated carbon as the catalyst carrier.A microwave heating reduction method was used to synthesize the catalyst Fe/C, Co/C and the electrochemical test results showed that they had good properties for ORR and OER. The ORR current density of Fe/C material was134mA/cm at-0.2V (vs. Hg/HgO) in alkaline conditions, and the OER current density was96.4mA/cm2at0.7V. The Co/C material had a current density of119mA/cm2at-0.2V, and146mA/cm2at0.7V. From the A.C impedance, the ohmic resistence was reduced to0.51Ω. A battery was set up to test the charge and discharge performances of Fe/C material at50mA/cm2. The results showed that the eletrode had a high charge voltage of over2.3V and poor cycle stability. The battery was distroyed within40hours.A microwave heating reduction method was also used to synthesize the FeCo/C catalysts. The X-ray of the material showed it contained with metal Fe and Co. The electrochemical results showed that the ratio of Fe and Co was1:1and the microwave time was6min would have a perfectible performance toward bifunctional air electrode. The current density of CoFe/C(1:1) was147mA/cm2at-0.2V and225.2mA/cm2at 0.7V. The charge voltage of the battery using Co-Fe/C as catalyst on air electrode was0.98V with the current of80mA/cm. Also a zinc-air battery made up by the same way could run in6M KOH at room temperature for118hours with a good stability at50mA/cm, where the discharge voltage of around1.0V and the charge voltage of lower2.15V. were obtained.