Iron addition to Vietnam anthracite coal and its nitrogen doping as a PEFC non-platinum cathode catalyst

The iron addition to Vietnam anthracite coal, subsequent nitrogen doping at 1073 K and its catalyst activity for the oxygen reduction reaction (ORR) were studied for application as an alternative platinum catalyst in a polymer electrolyte fuel cell. The ORR activity of the coal catalyst was determined by a three-electrode electrochemical measurement. The nitrogen doping without iron addition promoted hardly any activity of the Vietnam coal for the ORR, but the iron addition from 0.001 to 0.1 wt% caused a significant increase. The addition of 0.1 wt% iron to the Vietnam coal provided the highest ORR at 0.85 V vs. RHE at -0.005 mA/cm(2). However, the addition of 1.0 wt% iron formed several iron particles of 10-30 nm based on transmission electron microscopy measurement and decreased the ORR activity. From the X-ray photoelectron spectroscopy analysis of the non-added and iron-added Vietnam coals, the N/C, Fe/C and (Si + Al)/C ratios exhibited a maximum peak at the 0.005 wt% iron-added level, while the two latter ratios exhibited another high peak at 0.1 wt%. The nitrogen doping of Vietnam coal at 1073 K significantly increased from 5 to 1050 m(2)/g surface area with 96% slit-shaped micropores and generated nitrogen species having a disordered structure. The ORR activity of the treated Vietnam coal was related to the iron, nitrogen species and the ash components, such as Si and Al. The active structure of the iron added coal-derived electrocatalysts was discussed. (C) 2012 Elsevier Ltd. All rights reserved.