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Abstract: A nano-sized non-noble metal catalyst containing hemin supported on carbon black was synthesized for the oxygen reduction reaction (ORR). The hemin supported on carbon black was heat-treated (HT), and subjected to additional ultrasound treatments to increase the BET surface area and available active sites for the ORR. The HT hemin supported on carbon black was characterized with thermogravimetric analysis (TGA), elemental analysis, transmission electron microscopy (TEM), and BET surface area analysis. The catalytic activity of the synthesized electrocatalysts was analyzed with cyclic voltammetry (CV), rotating disk electrode (RDE), and rotating ring disk electrode (RRDE). The effect of BET surface area on formal potential, anodic and cathodic peak currents, limiting currents, half wave potentials, and kinetic rate constant for ORR were studied. We found an apparent correlation between catalytic activity and BET surface area for this particular catalyst. Increasing BET surface area, the ORR catalytic activity increases significantly. Our research on HT hemin indicates that the catalytic activity for ORR significantly improves by reducing the particle size and increasing the surface area. [Copyright &y& Elsevier]

Direct non-oxidative methane coupling (NMC) is one of the promising pathways for methane upgrading into value-added olefin and aromatic hydrocarbons. The silica-supported iron (i.e., Fe/SiO 2) catalyst has been reported effective for NMC, but the effects of silica support on the catalyst property and NMC performance have rarely been explored. In this work, we prepared a vitreous silica-supported iron (Fe/SiO 2 -V) catalyst by flame fusion of a mixture of quartz silica and fayalite. The physicochemical properties and NMC performance of the as-prepared catalysts were measured. Compared to crystalline cristobalite support in Fe/SiO 2 catalyst that has been studied previously, vitreous silica support has disordered Si-O bonds and structural defects, enabling better iron dispersion and more vital metal-support interaction. The as-prepared Fe/SiO 2 -V catalyst had a shorter induction period in methane activation and lower coke yield in NMC. The increase in iron concentration in Fe/SiO 2 -V catalysts elongated the catalyst induction period and promoted aromatics and coke formation. The coke type of the spent Fe/SiO 2 -V catalyst is more uniform than the cristobalite-supported iron catalyst. [Display omitted] • Vitreous silica-supported iron catalysts were prepared by an oxyhydrogen flame fusion method. • The amorphous vitreous silica support contains disordered and defective Si-O bonds. • Iron has higher dispersion and more uniform bonding in the vitreous silica support. • Vitreous silica-supported iron enabled fast methane activation and low coking in NMC. • Increase in iron loading in vitreous silica support promoted aromatics formation. [ABSTRACT FROM AUTHOR]