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Ru-implanted titanium near-surface alloys were generated by ion implantation, characterized (Ru concentration/ depth profiles) by Rutherford backscattering, and subsequently anodically oxidized to form electrocatalytically active RuxTil_xOJTi electrodes. The electrochemical behavior of the metallic-like electrodes was investigated in acidic chloride, perchlorate, and sulfate media. A correlation between the rate of the C12 evolution reaction and the Ru-implant profiles established that the reaction is first order in the concentration of Ru(IV) in the oxide at the oxide/solution interface, and enabled an in situ evaluation of the latter quantity. The Tafel slope for the C12 evolution reaction is 40 mV, i.e., o E/O log i = 2.303 (2RT/3F). The reaction order with respect to chloride ion concentration, 0 log i/0 log [C1-], approaches 1.0 and 2.0 at high and low chloride Concentrations, respectively. A modified Volmer-Heyrovsky mechanism, one in which the role of adsorbed chloride ions is taken into account, is shown to be consistent with the aforementioned diagnostic parameters.ion implantation, a nonequilibrium doping technique, enables the controlled introduction of virtually any element into the near-surface region of any substrate, typically to a depth up to a few hundred nanometers. The concentration/depth profile of the implanted species (determined, for example, by Rutherford backscattering) *Electrochemical Society Active Member. may be tailored over a wide range by varying the energy of the incident ions and the number of ions (coulombs of charge) implanted at each energy. As a surface modification technique, ion implantation has found widespread application for improving the electronic, optical, tribological, and corrosion characteristics of materials (1-4). The rates of many technologically important electrochemical charge transfer reactions occurring at elec-) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.255.6.125 Downloaded on 2015-06-03 to IP

Composition gradients, in molten AgNO3‐NaNO3 mixtures contained in silica frits, are produced by electrolysis between silver electrodes and analyzed by three methods: (i) in situ potentiometry, (ii) chemical analysis of sections of quenched electrolyte, and (iii) scanning electron microscopy with associated x‐ray fluorescence spectroscopy. The composition changes are calculated a priori from transport and thermodynamic properties independently measured in the free melt and corrected for the porosity of the frits. Since the ion flows in AgNO3‐NaNO3 are analogous to those in the normalLiCl‐normalKCl electrolyte of Li/S batteries, the former system serves as a convenient model system for the mixed electrolyte of the Li/S battery. The predicted gradients are compared to the experimental data from the three methods.

Separation of components has been measured in binary molten salt mixtures, AgNO3-KNO3, subjected to electrolysis between silver electrodes. The analysis of thin slices of frozen mixture contained in silica frits gives qualitatively the composition changes between anode and cathode and shows the expected enrichment of potassium ions at the cathode. Changes in concentration at the electrodes are measured electrochemically in free electrolytes and in electrolytes contained in frits. The time dependence of concentration at the electrodes is obtained both during electrolysis and during relaxation following electrolyses of different durations. The experimental results confirm the predictions from a mass transport model proposed previously for systems analogous to mixed molten salt batteries operated at high current densities.Electrolyte composition gradients in aqueous fuel cells and electrolyzers have been observed (2, 3) and explained in terms of electrode reactions, diffusion, and migration (4-6). Previously derived equations for (one dimensional) diffusion and migration in molten salt binary mixtures during current flow predicted the establishment of concentration gradients in the electrolytes of molten salt batteries and fuel cells (7). Such gradients have been reported, but not analyzed, in an A1/NaC1-KC1-A1C13/C12 battery (8) and in the electrolysis of LiBr-KBr mixtures for isotope separation (9). [Isotope separation by electrolysis of "pure" molten salt 6LiCI-?LiCt is itself an example of the development of composition gradients by virt~,e of difference of mobility (of 6Li+, ~Li+)] (10). These gradients, although potentially of significant magnitude and consequence in actual batteries (or fuel cells), are difficult to observe. Rapid back-diffusion during cooling imposes severe constraints on the sampling of such gradients for chemical analysis. In molten salt batteries (11, 12), variations of the potential between LiA1 and FeSz electrodes for reasons other than changes of the Li/K ratio of the LiC1-KC1 electrolyte tend to obscure in situ potentiometric measurement of the composition changes. Consequently, there is a need for suitable analog experiments to test the validity of the predictions.This paper presents the results of an experimental test of the predictions of the previously derived one dimensional equation for a system in which the electrode reaction, ion flows, and conditions of operation are analogous to those in a molten 'salt battery, but which is more amenable to quantitative analysis. We describe measurements of the composition changes in molten AgNO~-KNO~ mixtures subjected to electrolysis between two silver electrodes. Since silver, one of the two like-charged ions in the binary mixture, reacts at both electrodes, the ion flows are analogous * Electrochemical Society Active Member. Key words: molten salt, transport, battery.to those in the LiCI-KCI electrolyte of a Li/S battery, in which Li + ion enters the electrolyte at the anode and leaves at the cathode (11,12). Experiments were do...

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