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

Abstract

Biological reduction of O-2 to H2O justifies a serious look at heme as a potential O-2 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 A degrees 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 A degrees 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 A degrees 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 O-2 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 A degrees C.National Natural Science Foundation of China [20933004, 20833005, 20921120405

Biomass Derived N-Doped Porous Carbon Supported Single Fe Atoms as Superior Electrocatalysts for Oxygen Reduction

“…On the contrary, the TGA curve of the pure hemin presents three relatively obvious weight-loss waves (at ≈335, 430, and 710 °C), which are attributed to three different kinds of mass losses of the decomposition products. [32] It is worth noting that despite the similar trends of mass loss with pure hemin, the Hemin/NHPC only presents one weight-loss wave (≈445 °C), moving to the higher temperature region than those of the pure hemin, most probably due to the interactions between the functional groups in NHPC and eight short lateral chains (i.e., four methyl, two vinyl, and two propionyloxy groups) in the hemin molecules. In addition, the Hemin/NHPC composite exhibits the characteristic of hemin in the Fourier transform infrared ( Figure S1, Supporting Information) spectra, reconfirming that the NHPC has successfully adsorbed the hemin compound.…”

“…During the pyrolysis treatment, these interactions could form some new bonds to stabilize the Fe atoms and enhance the conductivity between the active sites and carbon supports. [32] In addition, the loading mass of hemin in the Hemin/NHPC, calculated by ultraviolet-visible ( Figure S2, Supporting Information) adsorption spectra, is ≈32%. Combined with the TGA data, the Hemin/NHPC with the pyrolysis temperature of 800 °C (i.e., SA-Fe/NHPC in the present study), can maintain 85.2% weight, which means the mass content of Fe is ≈2.3 wt% (see the calculation of Fe loading in the Supporting Information for details).…”

Effect of Heat Treatment on Activity of Fe/N/C Catalyst Prepared by Hemin for Oxygen Reduction Reaction

“…As reported in previous studies, by itself hemin has poor ORR activity [5]. The high ORR activity of the hemin-based catalyst is attributed to the FeN x ORR active sites formed by the calcination of hemin with carbon support [3]. These sites are thought to be embedded in the surface of the carbon supports (Fig.…”

“…3a). At a calcination condition of 600°C, 100 s, the spectrum shows a single peak at around 711 eV and corresponds to that of standard hemin [3]. This suggests that, at this calcination condition, most hemin remains without pyrolysis.…”

“…Previous work reported that the optimum calcination conditions are 600ºC, 2 h or 750ºC, 2 h for hemin-based catalysts [3,5]. On the other hand, Kamiya et al recently reported a Fe/N/C catalyst produced by instantaneous calcination (45 s) of pentaethylenehexamine coordinated with iron (Fe-PEHA) and graphenoxide [8,9].…”