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Abstract: The open circuit potentials (OCPs) of H2O2 at Pt, Pd, Au, and glassy carbon electrodes are measured in H2SO4 and NaOH electrolyte solutions. Effects of concentration of H+, OH− and H2O2 as well as temperature on the OCP of H2O2 are investigated. The OCP of H2O2 is much lower than its theoretical reduction potential in both acidic and basic medium. The OCP is actually a mixed potential of H2O2 electroreduction and electrooxidation simultaneously occurring at electrode surfaces and it is more close to the equilibrium potential of H2O2 electrooxidation rather than electroreduction. The OCP of H2O2 is around 0.77–0.80V at [H+]=[H2O2]=1.0moldm−3 in H2SO4 solution and is about 0–0.06V at [OH−]=[H2O2]=1.0moldm−3 in NaOH at 298K on Pt, Pd, Au and GC electrodes. The OCP of H2O2 is independent of H2O2 concentration within the range of 0.01 to 1.0moldm−3. It increases approximately linearly with the logarithm of H+ concentration from 0.02 to 2.0moldm−3, decreases with the logarithm of OH− concentration from 0.01 to 1.0moldm−3 and decreases with increase of temperature from 278K to 333K. The linear equations were presented and 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]

Bimetallic oxide CoMn 2 O 4 with nano-peony structure is prepared on Ni foam by a traditional hydrothermal process. Then constant-potential electrodeposition is applied to anchor Pd nanoparticles on CoMn 2 O 4 to form an electrode of Pd nanoparticles modified CoMn 2 O 4 (PCMN electrode) for H 2 O 2 electroreduction. The combination of Pd and CoMn 2 O 4 effectively reduces the dosage of noble metal. Besides, no binder is involved in the preparation which cuts the electrode cost and avoids the poor stability of traditional electrodes produced with binders. Scanning electron microscopy, X-ray diffraction and transmission electron microscopy are operated to investigate the structure and composition of the electrode. And the electrochemical behavior of the electrode is characterized by cyclic voltammetry and chronoamperometry. In 0.7 mol L−1 H 2 O 2 and 3 mol L−1 NaOH, a reduction current density of 580 mA cm−2 (normalized by geometric area) at −0.8 V on the electrode is obtained which reveals large capacity for actual application in H 2 O 2 -based fuel cell. A binder-free electrode of Pd nanoparticles anchored to nano-peony CoMn 2 O 4 was prepared and the synergy effect of Co, Mn and Pd highly improved the catalytic activity toward H 2 O 2 reduction. Unlabelled Image • Pd modified CoMn 2 O 4 electrode with special nano-peony structure was synthesized. • The special nano-peony structure provides more active sites for H 2 O 2 reduction. • The synergy effect of Co, Mn and Pd highly improved the catalytic activity. [ABSTRACT FROM AUTHOR]