The Study On The Air Electrode With TM-N/C Catalyst

Air electrode is metal-air battery and all types of fuel cell positive, the performanceof the air electrode restrict the rapid development of the battery. The air electrode ofoxygen reduction reaction (ORR), although in alkaline environment more easily thanthe acidic conditions, but the reaction process is complicated, kinetics reaction processis still relatively slow, exchange current density low, which is one of the key factors thatORR catalyst limited battery positive electrochemistry reaction activity. A highefficiency non-noble metal oxygen reduction reaction (ORR) catalyst labeled asCo-N/C(800) was prepared by heat-treatment process, and the air electrode waspreparated using the catalyst. It is researched several technique factors influencing theperformance of air electrode and established the optimum preparing technique which isapplied in practice, in this paper. The structure of Co-N/C(800) are studied by XRD.The electrocatalytic activity to ORR was investigated by linear sweep voltammetriccurves, polarization curves, as well as single fuel cell tests.The results show that the catalytic activity of Co-N/C(800) to ORR is good with anonset potential of0.04V (vs.Hg/HgO) in1mol/LNaOH, and is also good in4mol/LNH4Cl with an onset potential of0.23V (vs.SCE). Co-C/N(800) towards ORR isirreversible process, and the linear increase of peak current with the square root of thescan rate has indicated a diffusion controlled reduction.The air electrode is using the arrangement of catalytic layer/current collector/gasdiffusion layer. Air electrode with25%PTFE in active layer,60%PTFE in diffusionlayer and heating temperature at150℃without N2atmosphere show the bestperformance. A current density of100mA/cm2at-0.6V(vs.Hg/HgO) could be obtainedon the air-electrode using Co-N/C(800) as an electrocatalyst in7mol/L NaOH solutionon the condition of room temperature and air atmosphere. The negative electrode ofpure zinc and the electrolyte7mol/L NaOH were selected in the zinc-air cell, and thecurrent density exceeds100mA/cm2at-0.8V(vs.Hg/HgO), which is superior to MnO2catalyst. More importantly, the results of single cell test indicated that the cell dischargevoltage remain at1.25V~1.30V and the performance is very stable. Meanwhile, Zinc-aircell discharge test in4mol/L NH4Cl solution. The discharge voltage platform is high,the performance of air electrode is good.