FeN stabilized FeN@Pt core–shell nanostructures for oxygen reduction reaction

Abstract

The high cost and poor stability of catalysts are the main obstacles for the commercialization of proton exchange membrane (PEM) fuel cells, particularly, the catalysts for the oxygen reduction reaction (ORR). Here, PtFe nanocatalysts with different Pt to Fe atomic ratios are prepared by the impregnation-reduction method and subsequently thermal annealing in NH₃ at ambient pressure. XRD, STEM, XPS and ICP are employed to investigate the corresponding physico-chemical properties of the as-prepared catalysts, which demonstrate that the samples are Pt-rich core–shell nanostructures. The cyclic voltammetry method is used to investigate their electrochemical performance, and the results show that these catalysts display high ORR activity in O₂-saturated 0.1 mol L⁻¹ HClO₄ aqueous solutions, with PtFe₃N/C displaying the highest mass activity of 369.32 mA mg⁻¹ Pt in 0.90 V vs. RHE, which is about 3 times higher than that of a commercial Pt/C catalyst (129.15 mA mg⁻¹ Pt) at the same potential. Moreover, it is also found that the as-prepared catalysts are almost 2 times more stable than the commercial Pt/C. The ORR activity is slightly affected after 30k cycles in O₂-saturated HClO₄ aqueous solutions. This low cost ORR catalyst, which exhibits a high performance, opens up possibilities for designing core–shell nanostructures for energy conversion.