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The oxygen reduction reaction in sulphuric acid on commercial carbon supported platinum and ruthenium catalysts as well as on a home-made carbon supported ruthenium selenide catalysts (RuSe x /C) was investigated. The RuSe x /C catalysts were synthesised using similar procedures to those found in the literature. A dependency of H2O2 formation on the selenium content was found using the thin-film rotating ring disc electrode technique, namely that the H2O2 formation in the typical operation range of a Direct Methanol Fuel Cell (0.7–0.4 V) on Pt/C is below 1% and 1–4% on Ru/C and RuSe x /C catalysts. Finally for comparing the intrinsic activities of the catalysts the electrochemically active surface areas were determined in-situ by means of copper underpotential deposition. Our results indicate a comparable activity of the present RuSe x /C catalyst to commercial Pt/C if the activities are related to the electrochemical active areas. [ABSTRACT FROM AUTHOR]

The electrochemical behaviour of electrodeposited Co–Cu/Cu multilayers from citrate electrolytes was investigated using cyclic voltammetry and stripping techniques at a rotating ring disc electrode. Copper and cobalt–copper alloy sandwiches were deposited from an electrolyte containing 0.0125 M CuSO4, 0.250 M CoSO4 and 0.265 M trisodium citrate at two different pHs, 1.7 and 6.0. The Cu/Co–Cu/Cu sandwich is representative of a single layer in a Co–Cu/Cu multilayer deposit, which is known to exhibit unusual physical and magnetic properties. Results from cyclic voltammetry and detection of dissolving species at the ring showed that cobalt is stripped from a Cu/Co–Cu/Cu sandwich even when a copper layer as thick as 600 nm covers the Co–Cu alloy. Scanning electron microscopy showed that cobalt can dissolve from the deposit easily because the copper layer covering the Co–Cu alloy is porous. A separate series of experiments with Cu/Co–Ni–Cu/Cu sandwich showed that cobalt does not dissolve from these deposits because the addition of nickel stabilises cobalt in the Co–Ni–Cu alloy. [ABSTRACT FROM AUTHOR]

The electrocatalytic activity of several materials for the nitrate reduction reaction was studied by cyclic voltammetry on a rotating ring disc electrode in solutions with different concentrations of sodium bicarbonate. Copper exhibited highest catalytic activity among the materials studied. Nitrate reduction on copper was characterized by two cathodic shoulders on the polarization curve in the potential region of the commencement of hydrogen evolution. In this potential range an anodic current response was observed on the Pt ring electrode identified as nitrite to nitrate oxidation. This indicates that nitrite is an intermediate product during nitrate reduction. These conclusions were verified by batch electrolysis using a plate electrode electrochemical cell. Copper and nickel, materials representing the opposite ends of the electrocatalytic activity spectra, were used in batch electrolysis testing. [ABSTRACT FROM AUTHOR]