Phosphorus-doped And Phosphorus And Iron/Cobalt Co-doped Carbon As Efficient Electrocatalysts For Oxygen Reduction Reaction

The sluggish kinetics of oxygen reduction reaction limits the performance of the fuel cells and metal-air batteries. The platinum-based electrocatalysts impede the large-scale commercialization of fuel cells and metal-air batteries due to their high cost and limited supply. In this thesis, carbon-based materials with low price, high earth abundance and environmental friendliness have been studied as electrocatalysts for the oxygen reduction reaction(ORR). The structure of carbon has been modified through the doping of phosphorous and co-doping of phosphorous and transition metal(iron/cobalt). In this way, the catalytic active sites of carbon can be tailored and the catalytic activity and stability of carbon for ORR can be enhanced. A phosphorus doped carbon nanotube(P-CNT) has been facilely synthesized via a one-step in-situ solvothermal approach at a low temperature of 500 ℃. The catalytic activity and stability of P-CNT for ORR in alkaline media has been studied in detail. In order to further improve the catalytic activity of the heteroatom doped carbon materials, a dual doping process has been adopted in this study. A phosphorus and iron co-doped carbon xerogel(P-Fe-C) has been synthesized via an in situ sol-gel polymerization method followed by a pyrolysis process. The influence of pyrolysis temperature, doping content of the heteroatom and microstructure of the materials on the electrocatalytic activity of carbon for ORR has been extensively studied. The active site of phosphorus and iron co-doped carbon for ORR has been proposed. To investigate the effect of different co-doping transition metal elements, a phosphorus and cobalt co-doped graphene(P-Co-G) has been synthesized via an electrostatic assembly method followed by a pyrolysis process. The influence of doping content of P and Co on the catalytic activity of graphene for ORR has been systematically studied. The effect of different co-doping elements(Fe and Co) on the ORR activity of dual doped graphene has been compared. In addition, the catalytic activity of the as-prepared heteroatom doped carbon for oxygen evolution reaction(OER) has also been explored.