Study of pyrolyzed hemin/C as non-platinum cathodic catalyst for direct methanol fuel cells

Abstract: Biological reduction of O₂ to H₂O justifies a serious look at heme as a potential O₂ reduction reaction (ORR) catalyst for low temperature fuel cells. In this study, a novel non-platinum electrocatalyst for ORR was prepared through hemin, which is hydrochloride of heme, supported on Black Pearls 2000 carbon black (Hm-BP) pyrolyzed at 700–900 °C in Ar atmosphere. The physical and electrocatalytic properties of as-prepared catalysts were characterized by TGA, XRD, XPS, TEM, rotating disk electrode (RDE) and rotating ring disk electrode (RRDE). It has found that the catalyst treated at 750 °C (Hm-BP-750) exhibits the best property among the Hm-BP catalysts prepared. The onset potential of ORR on the Hm-BP-750 at 30 °C was measured ca. 0.90 V (vs. RHE) in 0.1 M H₂SO₄, and mass current density was reached 15.3 mA mg⁻¹ at 0.75 V. It has revealed that O₂ could be reduced directly to water in a 4e process between 0.9 and 0.83V, and the yield of H₂O₂ was 0–18% in the potential range of 0.83–0.63 V. This methanol-tolerant catalyst also presents excellent stability in medium-term test of direct methanol fuel cell at 80 °C.