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Free keywords:
Fuel cell catalysis; Heteroatom doping; Ordered mesoporous carbon; Oxygen reduction reaction
Abstract:
In order to elucidate the role of B, N, and P dopants in carbon materials on the kinetics of oxygen reduction reaction (ORR) and to provide a fair comparison of the effects of each dopant, a series of ordered mesoporous carbons (OMCs) with low concentration of heteroatoms (< 1 at%) has been prepared. Doped OMCs were characterized using X-ray photoelectron spectroscopy (XPS), inductively coupled plasma optical emission spectroscopy (ICP-OES), Raman spectroscopy, X-ray powder diffraction (XRD), and N-2 physisorption measurements. Comparative study of the ORR activity of these materials in alkaline solution was performed using rotating disk electrode voltammetry. The experiments evidenced that, compared to non-doped OMC, charge transfer kinetics was improved independently on the nature of the heteroatom. The decrease of the ORR overvoltage and the increase of the mass activity upon doping are similar for B and P and less prominent for N. On the other hand, OMCs doped with low levels of B and N were found to be selective for O-2 reduction to peroxide, while for P-doped OMCs, the apparent number of electrons consumed per O-2 molecule was up to 3.1. Experimental measurements were complemented by density functional theory (DFT) calculations.
