The kinetics of the electrochemical oxidation of a CO adlayer on Pt[n(111)×(111)] electrodes in 0.5 M H 2 SO 4 has been studied using chronoamperometry. The objective is to elucidate the effect of the crystalline defects on the rate of the reaction by using a series of stepped surfaces. The reaction kinetics of the main oxidative process can be modeled using the mean-field approximation for the Langmuir-Hinshelwood mechanism, implying fast diffusion of adsorbed CO on the Pt[n(111)×( 111)] surfaces under electrochemical conditions. The apparent rate constant for the electrochemical CO oxidation, determined by a fitting of the experimental data with the mean-field model, is found to be proportional to the step fraction (1/n) for the surfaces with n > 5, proving steps to be the active sites for the CO adlayer oxidation. An apparent intrinsic rate constant is determined. The potential dependence of the apparent rate constants is found to be structure insensitive with a Tafel slope of ca. 80 mV/dec, suggesting the presence of a slow chemical step in an ECE reaction mechanism.

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The adsorption of CO and the electrochemical oxidation of a CO adlayer on stepped Pt electrodes, Pt(443), Pt(332), and Pt(322), has been studied using in situ infrared reflection−absorption spectroscopy (IRAS). Coverage-dependent and potential-dependent spectra of CO adlayers on stepped Pt surfaces are reported. Infrared spectra acquired during oxidation of the CO adlayer provide information on the mechanism of the reaction and the structure of the operational catalytic active site. CO adsorbed on the (111) terraces is found to be more reactive compared to that adsorbed on either (110) or (100) steps. The step trough of either (110) or (100) step is concluded to be the active site for the electrocatalytic oxidation of the CO adlayer, the most reactive combination involving CO from the terrace and an oxygen-containing species in the step trough.

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The electrochemical oxidation of carbon monoxide and methanol on single-crystal noble metal electrodes has been studied using cyclic voltammetry, chronoamperometry, in situ FTIR spectroscopy, online electrochemical mass spectrometry, and theoretical methods. The oxidation of CO was found to be enhanced by steps and defects. Furthermore, the surface diffusion rate was found to have a significant influence on the kinetics of the oxidation process: for high diffusion rates, such as the oxidation of CO on platinum, the kinetics can be described by a mean field model, while for low diffusion rates, such as CO oxidation on rhodium in sulfuric acid, a nucleationand-growth model was found to be more suitable. Voltammetric and mass spectrometric measurements on the oxidation of methanol on platinum indicate that steps enhance the overall reaction rate. In general, the selectivity towards the direct oxidation pathway through soluble intermediates was found to be higher in the absence of strongly adsorbing anions. In both perchloric and sulfuric acid, this selectivity was also found to increase with increasing step density. In sulfuric acid, Pt(111) shows the highest relative contribution for the direct pathway of all surfaces studied in that electrolyte. Based on these results, a detailed reaction scheme for the electrochemical oxidation of methanol is presented.

The objective of this study is to evaluate chemical hazards and risks associated with the accidental release of Li-ion battery electrolyte into an enclosed space. Because of the high volatility and reactivity of some components of contemporary Li-ion battery electrolytes this study focuses on the inhalation toxicity of released and generated gas phase components. These include evaporated solvents and HF as a decomposition product of the widely used LiPF 6 salt. Our calculations show that at room temperature a small electrolyte release can result in the formation of a toxic atmosphere with concentration of the released compound reaching an acute exposure limit where irreversible and other serious health effects are expected to occur. For most contemporary electrolyte components this corresponds to a release of less than ca. 250 ml in a volume occupied by a medium-size car with a clearance of 1 m, i.e. ca. 62 m 3 . Further research, required as part of the thorough risk analysis, is identified.

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