Phosphorus doping of graphite and its applications as energy materials

Shimoyama, Iwao   ; Baba, Yuji  

Carbon alloy is a series of materials prepared by heteroatom doping in -conjugated carbon materials and recently attracts much attention due to some functionalities such as catalytic activity. We study the changes of two functionalities, catalytic activity on oxygen reduction reaction and adsorptive desulfurization property for thiophene, induced by phosphorus doping in graphite. The configurations at phosphorus sites were investigated by near-edge X-ray absorption fine structure spectroscopy and molecular orbital (MO) calculations, and we clarified that phosphorus sites formed planar and curved configurations depending on substrate temperature during ion doping. We also found that curved phosphorus-doped graphite had better catalytic activity and desulfurization property when curved configuration was preferentially formed. Comparison between phosphorus and nitrogen dopings suggests that phosphorus is superior to nitrogen with regard to adsorptive desulfurization. We interpreted these experimental results based on MO calculations and clarified the role of phosphorus as a dopant.