Ammonia-treated brown coal and its activity for oxygen reduction reaction in polymer electrolyte fuel cell

Coal has been utilized as a nonprecious metal catalyst for the oxygen reduction reaction (ORR) in a polymer electrolyte fuel cell. The Australia brown coal was nitrogen-doped at 673-1123 K in a stream of NH3. The raw and NH3-treated Australia brown coals were characterized on the basis of their N-2 adsorption, Raman spectroscopy and X-ray photoelectron spectroscopy. The nitrogen doping of the coal at 1073 K increased the BET surface area from 10 to 671 m(2)/g having 95% slit-shaped micropores with a type I monolayer adsorption. The nitrogen-doped coal at 1073 K exhibited the highest potential of 0.85 V vs. RHE (at -0.005 mA/cm(2)), which was evaluated by three-electrode electrochemical measurements using a rotating ring disk electrode in a 0.5 M H2SO4 aqueous solution. The ORR activity of the nitrogen-doped coal was related to the pyridine-N species, microporosity and degree of disordered carbons in the coal. The iron addition to the coal from 10 to 10(3) ppm increased the ORR onset potential. The active structure of the coal-derived catalyst was discussed based on the results of the XPS, Raman, N-2 adsorption and iron effect. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.