Preparation And Properties Of Phosphorus-doped Carbon Catalysts For Anion Membrane Fuel Cells

Anion exchange membrane fuel cell(AEMFC)has become a research hotspot at home and abroad because cathode can use non-noble metal catalysts,is not easy to poison by CO,and requires low performance of bipolar plates.The development of novel and efficient non-noble metal or non-metal cathodic oxygen reduction reaction(ORR)catalysts has important theoretical significance and application value for promoting the application and development of anionic membrane fuel cells.In this paper,P-doped carbon catalysts were prepared by in-situ doping and pyrolysis with different phosphorus and carbon sources.The electrochemical properties of P-doped carbon catalysts were studied by changing the amount of phosphorus and carbonization temperature.Firstly,P-doped XC-72 carbon catalysts were prepared by one-step pyrolysis using triphenylphosphorus and XC-72 with good conductivity.Different catalysts were prepared by changing the amount of phosphorus and carbonization temperature.The results show that the P-doped carbon is graphitized mesoporous carbon with C-P and O-P bonds.When the ratio of carbon source to phosphorus source is 1:5 and the carbonization temperature is 800?,the catalyst has a positive onset potential(-0.12 V)and a well current density(4.73 mA/cm2).The number of transfer electrons is 3.63 e.It is the ORR reaction process of four-electron and two-electron pathways and the main oxygen reduction process of four-electron transfer.The ratio of precursor has little effect on the catalytic performance,and the carbonization temperature can change the electrocatalytic performance by changing the graphitization degree.In order to further improve the catalytic activity of P-doped porous carbon materials,P-doped porous network carbon ORR catalysts with graphitization and multiple defects were prepared by one-step pyrolysis double activation method using glucose as carbon source,NaH2PO2 as phosphorus source and ZnC12 as activator.The pore size and morphology of the catalyst were controlled by controlling the amount of phosphorus and carbonization temperature,and C-P and O-P bonds were formed after P doping.When NaH2PO2 content is 0.4 g and carbonization temperature is 750 C,the maximum limit current density(6.40 mA/cm2)of the sample is obtained.After 2000 cycles,the current density decreases by 47 mA/cm2,showing good stability.In order to further reduce the cost,Porous Carbon ORR catalyst with P-doped pomelo peel was prepared by treating pomelo peel with potassium phosphate,phosphoric acid and sodium hypophosphite.Porous carbon was prepared from pomelo peel treated with sodium hypophosphite as pore-forming agent and P source.Porous carbon was doped with P in the presence of C-P and O-P bonds.When the mass of the sample was 2 g,the ORR starting potential was-0.08V,the limiting current density was 3.60 mA/cm2,and the current density was reduced by 0.53 mA/cm2 after 2000 cycles,showing good stability.