Research On Low-platinum Catalysts For Fuel Cells Supported On Non-platinum Catalysts

Fuel cells have attracted scholars’research and attention because of their high theoretical capacity,high energy conversion rate and environmental friendliness.However,fuel cells still need to use expensive platinum-based catalysts for oxygen reduction reaction（ORR）.The high cost limits its stable development and universal application.The most promising non-noble metal catalysts to replace expensive platinum-based catalysts are M-N-C materials prepared by CO doping pyrolysis transition metals（Fe,Co,Mn,etc.）with nitrogen.In supported catalysts,the dispersion of active metal particles is related to the support,and its pore structure distribution,surface properties and composition are the core elements that determine its performance.Therefore,to improve the utilization rate of catalysts,materials with a large specific surface area are often used as carriers and loaded with catalyst particles.The main work of this paper is as follows:1.In this paper,the ECP600JD carrier was treated with concentrated nitric acid,and the BET test was carried out on the ECP600JD carrier with different treatment time.The results showed that the specific surface area of ECP600JD decreased,but the pore diameter did not change after acidification;FT-IR and acid group alkali consumption test showed that the oxygen-containing functional groups on the surface of ECP600JD treated with acid for 24hours were 1.7 times higher than that of ECP600JD without acid treatment;XRD and Raman spectra showed that the carbon defects increased and the graphitization degree was high after acidification;The electrochemical test results show that the electrochemical performance and stability of ECP600JD carrier treated with acid for 24 hours are the best.2.Pt/ECP600JD-X catalyst was prepared by ethylene glycol reduction method with ECP600JD before and after pretreatment as the carrier.Transmission electron microscope showed that Pt particles had better dispersion on the surface of acid-treated carrier;The half wave potentials of Pt/ECP600JD-24 h in 0.1 mol·L^-1 HCl O₄ and 0.1 mol·L^-1 KOH are 0.57 V and 0.88 V respectively;The ECSA of Pt are 83.32 m²g _Pt^-1 and 64.14 m²g _Pt^-1 respectively;After 1000 cycles,the residual ECSA are 64.95%and 62.53%respectively.This data shows that Pt/ECP600JD-24 h has better electrochemical performance.3.Co-N/C-X oxygen reduction catalyst was prepared by pyrolysis of ECP600JD-24 h with cobalt acetate tetrahydrate in an ammonia atmosphere at different temperatures.After ammonia heat treatment,the XRD results showed that Co_5.47N/C was formed from ECP600JD and cobalt acetate tetrahydrate.After calcination at 800℃,the prepared Co-N/C catalyst has the best electrocatalytic performance.In acidic and alkaline electrolyte solutions,the half-wave potential are 0.48 V and 0.85 V,respectively,and it is a four-electron transfer process.4.Prepare Pt/CoNC-X catalyst with Co-N/C-X as support.The prepared Pt/CoNC-800 is evenly dispersed without agglomeration,and the particle size of Pt is 2.59 nm.In acidic and alkaline electrolyte solutions,ECSA are 90.05 m²g _Pt^-1 and 95.11 m²g _Pt^-1;After 1000 cycles,the residual ECSA are 78.42%and 69.15%,respectively;The half wave potential reach 0.62V and 0.85 V respectively,which had good ORR electrocatalytic performance.It is found that the ORR performance and stability of Pt/CoNC-X catalyst prepared with Co-N/C-X as carrier are higher than those of Pt/ECP600JD-X catalyst.