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Non-precious-metal catalysts (NPMC) are promising alternatives to platinum-based catalysts for the oxygen reduction reaction (ORR), which is the cathode reaction in fuel cells. In this paper, we focus on an iron–nitrogen–carbon (Fe/N/C) catalyst, in comparison to platinum, and investigate how these different types of catalysts behave toward selective anion poisoning. The catalysts are studied with respect to their ORR activity, using the rotating disk electrode (RDE) technique in aqueous HClO4, H2SO4, H3PO4, and HCl electrolytes, and the results are supported by density functional theory (DFT) calculations. We find that the ORR on the Fe/N/C catalyst is less affected by anion poisoning than platinum. Surprisingly, it is seen that phosphoric acid not only does not poison the Fe/N/C catalyst, but instead promotes the ORR; this finding is in sharp contrast to the poisoning effect observed on platinum. This is a highly important finding, as modern high-temperature proton exchange fuel cells (HT-PEMFCs) employ membranes consisting of phosphoric acid that is immobilized into a polybenzimidazole (PBI) matrix.

Iron carbide encapsulated in graphitic layers has recently been recognized as an active oxygen reduction reaction (ORR) catalyst made of earthabundant elements. Here, the ORR activity of graphene (G) and N-doped graphene (NG) supported on Fe 3 C(010) and Fe( 110) is studied computationally by means of density functional theory calculations. The calculations show higher activity of the Fe 3 C-supported model system than the Fe-supported one, as well as the importance of N-doping in achieving high ORR activity, in agreement with experimental observations. We find the most active sites on a single N-doped graphitic layer placed on the Fe 3 C surface. Like in the case of unsupported NG, the reaction on the Fe 3 C/NG model interface proceeds at the atomic oxygen coverage between 0.5 < θ O < 1.0. The charge on O adsorbate caused by the presence of support is found to correlate with the oxygen binding strength. In the case of the Fe/NG system, this results in a surface poisoning by oxygen. On the basis of these findings, we propose that a heterostructure consisting of a NG overlayer and a support with stronger electron-donating properties than Fe 3 C and weaker than Fe may approach or even exceed the ORR activity of the Pt(111) surface.

Metal and nitrogen codoped carbons (M−N/Cs) have emerged as promising alternatives to platinum‐based catalysts for the oxygen reduction reaction (ORR). DFT calculations are used to investigate the adsorption of anions and impurities from the electrolyte on the active site, modeled as an M−N4 motif embedded in a planar carbon sheet (M=Cr, Mn, Fe, Co). The two‐dimensional catalyst structure implies that each metal atom has two potential active sites, one on each side of the sheet. Adsorption of anions or impurities on both sites results in poisoning, but adsorption on one of the sites leads to a modified ORR activity on the remaining site. The calculated adsorption energies show that a number of species adsorb only on one of the two sites under realistic experimental conditions. Furthermore, a few of these adsorbates modify the adsorption energies of the ORR intermediates on the remaining site, in such a way that the limiting potential is improved.

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