TY - JOUR A1 - Kobayashi, Rieko A1 - Ishii, Takafumi A1 - Imashiro, Yasuo A1 - Ozaki, Jun-ichi T1 - Synthesis of P- and N-doped carbon catalysts for the oxygen reduction reaction via controlled phosphoric acid treatment of folic acid JF - Beilstein Journal of Nanotechnology PY - 2019/// VL - 10 SP - 1497 EP - 1510 SN - 2190-4286 DO - 10.3762/bjnano.10.148 PB - Beilstein-Institut JA - Beilstein J. Nanotechnol. UR - https://doi.org/10.3762/bjnano.10.148 KW - folic acid KW - oxygen reduction reaction KW - phosphoric acid treatment KW - PN-doped carbon catalysts KW - polymer electrolyte fuel cells N2 - Herein, we synthesized P- and N-doped carbon materials (PN-doped carbon materials) through controlled phosphoric acid treatment (CPAT) of folic acid (FA) and probed their ability to catalyze the oxygen reduction reaction (ORR) at the cathode of a fuel cell. Precursors obtained by heating FA in the presence of phosphoric acid at temperatures of 400–1000 °C were further annealed at 1000 °C to afford PN-doped carbon materials. The extent of precursor P doping was maximized at 700 °C, and the use of higher temperatures resulted in activation and increased porosity rather than in increased P content. The P/C atomic ratios of PN-doped carbon materials correlated well with those of the precursors, which indicated that CPAT is well suited for the preparation of PN-doped carbon materials. The carbon material prepared using a CPAT temperature of 700 °C exhibited the highest ORR activity and was shown to contain –C–PO2 and –C–PO3 moieties as the major P species and pyridinic N as the major N species. Moreover, no N–P bonds were detected. It was concluded that the presence of –C–PO2 and –C–PO3 units decreases the work function and thus raises the Fermi level above the standard O2/H2O reduction potential, which resulted in enhanced ORR activity. Finally, CPAT was concluded to be applicable to the synthesis of PN-doped carbon materials from N-containing organic compounds other than FA. ER -