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Abstract: We report a new method of preparation of a methanol-tolerant Se/Ru cathode catalyst for the direct methanol fuel cell (DMFC) , whereby selenium is deposited on ruthenium nanoparticles by H2-reduction of SeO2 in aqueous solution at room temperature. The obtained Se/Ru(aq) was studied by electrochemical measurements and tested as a cathode catalyst in H2–air and direct methanol fuel cells. The new catalyst formulation (Se/Ru(aq)) is shown to be superior to Se/Ru synthesized from xylenes solvent and to Ru black by RRDE measurements, in terms of both activity and selectivity for complete oxygen reduction to water. Although Ru black is less active, the Tafel slopes and activation energies of Se/Ru catalysts and reduced-Ru black are similar, implying similar ORR mechanisms. In H2–air fuel cell tests, Se/Ru(aq) was more active than Se/Ru(xyl) at all voltages. Compared to Ru black, Se/Ru(aq) was superior at low current densities, but Ru black slightly exceeded the performance of Se/Ru at high current densities. To explain the RRDE and fuel cell observations, the two roles of Se as an inhibitor of Ru oxidation and as a site-blocker are discussed. [Copyright &y& Elsevier]

Abstract: The synthesis, electrochemical analysis, and hydrogen-air fuel cell testing results for a new type of Se/Ru catalyst called Se/Ru(aq) were described in Part 1. In this second report, we present methanol tolerance studies and direct methanol fuel cell testing for the same catalyst. A “methanol-tolerant” catalyst does not oxidize methanol, nor becomes depolarized by its presence, which is a desirable property for DMFC cathodes used with methanol-permeable membranes or in mixed-reactant designs. In perchloric acid electrolyte, the Se/Ru(aq) catalyst was found to be highly tolerant to 1.0M methanol. More importantly, in fuel-cell testing as a DMFC cathode, Se/Ru(aq) was shown to be highly tolerant to methanol crossing through the membrane (from the anode side) up to a feed concentration of 17M. The results were compared to those obtained using unmodified Ru black and Pt black at the DMFC cathode, in order to gain insight into the catalyst function and to compare the performance to relevant benchmarks. Compared to Pt cathodes, the performance of Se/Ru(aq) is significantly better at high methanol concentrations (e.g., 17M), suggesting their use either in DMFCs with high methanol feed concentrations or in mixed-reactant fuel cells. [Copyright &y& Elsevier]

Ni foam supporting flower-like Co nano-particles (Co NFs/Ni foam) are successfully synthesized by a simple electrochemical method. The electrodes are characterized by scanning electron microscopy equipped with an energy dispersive X-ray spectrometer, and X-ray diffractometer. Without any conducting carbons and polymer binders, the 3D electrode with a unique structure is directly used as the noble metal-free catalyst for hydrazine oxidation and the catalytic performance is evaluated by voltammetry and chronoamperometry. The Co NFs/Ni foam electrode exhibits excellent catalytic performance and superior stability for hydrazine electrooxidation in alkaline media. In the solution of 1.0 mol L − 1 NaOH + 30 mmol L − 1 N 2 H 4 , the oxidation current density at − 0.8 V is 140 mA cm − 2 for the Co NFs/Ni foam electrode, and it is only 42 mA cm − 2 for the Pt/Ni foam electrode. Also, the onset potential for Co NFs/Ni foam electrode can reach to − 1.06 V (only − 0.72 V for Ni foam), suggesting that the high cell voltage of DHFC with Co NFs/Ni foam anode. These merits are benefitting from the unique 3D structure which can ensure high utilization of catalysts. [ABSTRACT FROM AUTHOR]

Strengthening electrical conductivity and multiple atomic interaction are benefit for improving activity of oxygen evolution reaction (OER). Herein, we synthesized Fe-Doped NiSe 2 nanospheres distribute on reduced graphene oxide sheets (Ni 0.7 Fe 0.3 Se 2 /rGO). The optimum ratio (30%) of rGO was ascertained by comparing the properties of catalysts with different rGO amounts. In alkaline electrolyte, the Ni 0.7 Fe 0.3 Se 2 /rGO-30% owns the better OER performance than those of Ni 0.7 Fe 0.3 Se 2 and NiSe 2 , ascribed to the unique architecture that Ni 0.7 Fe 0.3 Se 2 nanospheres decorate rGO. In the architecture, the rGO matrix increases conductivity, enlarges transfer rate of ions and electrons and promotes dispersion of Ni 0.7 Fe 0.3 Se 2. In addition, multiple atomic interaction of Ni/Fe atoms and the synergistic effect between the Ni 0.7 Fe 0.3 Se 2 and rGO enable the compound to be an efficient OER catalyst. Through the rational analysis, Ni 0.7 Fe 0.3 Se 2 /rGO-30% hybrid is promising as an effective non-noble metal catalyst for OER application. • The Ni 0.7 Fe 0.3 Se 2 nanospheres uniformly decorate the rGO. • Multiple atomic interaction contributes to better OER activities. • The rGO increases conductivity of composite and accelerates charge transfer rate. • The content of rGO in composites affects the OER performance. [ABSTRACT FROM AUTHOR]