Study On Non Platinum Cathode Catalyst For Vehicle Fuel Cell

Fuel cell vehicles?FCVs?are quite promising in the field of new energy vehicles because of their low carbon emission,environmental friendliness and high conversion efficiency.However,the kinetics of oxygen reduction reaction?ORR?on the cathode of fuel cell is slow.Therefore,finding appropriate catalyst to improve the reaction rate has become a research hotspot in this field.At present,the most efficient oxygen reduction catalyst is still platinum and its alloy materials.However,the high cost,poor durability and resource shortage of platinum and its alloy materials limit their large-scale commercial use.Therefore,it is particularly important to find non-noble metal catalysts that can replace platinum materials.In this paper,metal organic framework materials were used as precursors to synthesize oxygen reduction electrocatalysts by pyrolysis.The relationship between the structure and oxygen reduction performance of the catalysts was studied based on the characterization results of the catalysts,which provided insight for the preparation of low-cost,efficient and stable non platinum cathode oxygen reduction catalyst for fuel cells.In this paper,ZIF-67 precursor with uniform particles and specific rhombic shape was synthesized by room temperature stirring.Then,ZIF-67 derived metal nitrogen carbon material?CoNC-T,T represents the pyrolysis temperature?was prepared by pyrolysis of ZIF-67 as sacrificial template in nitrogen environment at 600?,700? and 800?,and its oxygen reduction reaction performance in alkaline environment was tested.The results show that CoNC-600,CoNC-700 and CoNC-800which are obtained by pyrolysis,have similar oxygen reduction properties.The effects of inorganic salts on the physicochemical properties and oxygen reduction properties of ZIF-67 derivatives were further investigated.The precursors ZIF-67-NaCl,ZIF-67-Na₂CO₃ and ZIF-67-K₂CO₃ were prepared by impregnation by adding inorganic salts such as NaCl,Na₂CO₃ and K₂CO₃ into the precursor ZIF-67.Then,they were pyrolyzed at high temperature in nitrogen environment to obtain CoNC-NaCl,CoNC-Na₂CO₃ and CoNC-K₂CO₃ derived material catalysts.The results show that the addition of inorganic salts has obvious effect on the oxygen reduction performance of ZIF-67 derived material catalyst.The addition of NaCl can improve the oxygen reduction performance of the catalyst,but the addition of Na₂CO₃ and K₂CO₃ reduce the oxygen reduction performance of the catalyst.In order to further explore the effect of NaCl on the performance of the catalyst,the effects of NaCl addition and pyrolysis temperature on the catalytic activity of the catalyst were investigated.The experimental results show that CoNC-1NaCl-800has better catalytic performance,and its half wave potential is 0.84 V?vs.RHE?,which is equivalent to commercial 20wt%Pt/C catalyst(half wave potential is 0.86 V?vs.RHE?.The stability of CoNC-1NaCl-800 was better than that of commercial Pt/C under alkaline condition.After 7500cycles of CV scanning,the half wave potential of CoNC-1NaCl-800decreased by 6 m V,which was much lower than that of commercial Pt/C?29 mV?.