The application of naive Koutecky-Levich analysis to micro- and nano-particle modified rotating disk electrodes of partially covered and non-planar geometry is critically analysed. Assuming strong overlap of the diffu...The application of naive Koutecky-Levich analysis to micro- and nano-particle modified rotating disk electrodes of partially covered and non-planar geometry is critically analysed. Assuming strong overlap of the diffusion fields of the particles such that transport to the entire surface is time-independent and one-dimensional, the observed voltammetric response reflects an apparent electrochemical rate o constant koapp, equal to the true rate constant ko describing the redox reaction of interest on the surface of the nanoparticles and the ratio,ψ, of the total electroactive surface area to the geometric area of the rotating disk surface. It is demonstrated that Koutecky-Levich analysis is applicable and yields the expected plots of I-1 versus ω-1 where I is the current and ω is the rotation speed but that the values of the electrochemical rate constants inferred are thereof koapp, not ko. Thus, for ψ 〉 1 apparent electrocatalysis might be naively but wrongly inferred whereas for ψ 〈 1 the deduced electrochemical rate constant will be less than ko. Moreover, the effect of ψ on the observed rotating disk electrode voltammograms is significant, signalling the need for care in the overly simplistic application of Koutecky-Levich analysis to modified rotating electrodes, as is commonly applied for example in the analysis of possible oxygen reduction catalysts.展开更多
39 mol% SiC of ceramic pellets ZrB<sub>2</sub>-αSiC and TiB<sub>2</sub>-αSiC were synthesized by the reactive hot pressure RHP process at 1850°C under 40 Mpa in vacuum. The XR diffrac...39 mol% SiC of ceramic pellets ZrB<sub>2</sub>-αSiC and TiB<sub>2</sub>-αSiC were synthesized by the reactive hot pressure RHP process at 1850°C under 40 Mpa in vacuum. The XR diffraction displays the absence of other reagents apart from ZrB<sub>2</sub>, SiC and TiB<sub>2</sub> confirming the purity of the pellets. The cathodic exploitation of both of them through electrochemical study shows that TiB<sub>2</sub>-αSiC is the most active for Hydrogen Evolution Reaction (HER) and Hydrogen Oxidation Reaction (HOR) in 0.5 M of H<sub>2</sub>SO<sub>4</sub> solution at room temperature. Moreover, the kinetic exploitation shows that for both pellets the system is controlled by mass transport when they are used as HER. However, in the case of HOR, the system is controlled by the electron transfer.展开更多
文摘The application of naive Koutecky-Levich analysis to micro- and nano-particle modified rotating disk electrodes of partially covered and non-planar geometry is critically analysed. Assuming strong overlap of the diffusion fields of the particles such that transport to the entire surface is time-independent and one-dimensional, the observed voltammetric response reflects an apparent electrochemical rate o constant koapp, equal to the true rate constant ko describing the redox reaction of interest on the surface of the nanoparticles and the ratio,ψ, of the total electroactive surface area to the geometric area of the rotating disk surface. It is demonstrated that Koutecky-Levich analysis is applicable and yields the expected plots of I-1 versus ω-1 where I is the current and ω is the rotation speed but that the values of the electrochemical rate constants inferred are thereof koapp, not ko. Thus, for ψ 〉 1 apparent electrocatalysis might be naively but wrongly inferred whereas for ψ 〈 1 the deduced electrochemical rate constant will be less than ko. Moreover, the effect of ψ on the observed rotating disk electrode voltammograms is significant, signalling the need for care in the overly simplistic application of Koutecky-Levich analysis to modified rotating electrodes, as is commonly applied for example in the analysis of possible oxygen reduction catalysts.
文摘39 mol% SiC of ceramic pellets ZrB<sub>2</sub>-αSiC and TiB<sub>2</sub>-αSiC were synthesized by the reactive hot pressure RHP process at 1850°C under 40 Mpa in vacuum. The XR diffraction displays the absence of other reagents apart from ZrB<sub>2</sub>, SiC and TiB<sub>2</sub> confirming the purity of the pellets. The cathodic exploitation of both of them through electrochemical study shows that TiB<sub>2</sub>-αSiC is the most active for Hydrogen Evolution Reaction (HER) and Hydrogen Oxidation Reaction (HOR) in 0.5 M of H<sub>2</sub>SO<sub>4</sub> solution at room temperature. Moreover, the kinetic exploitation shows that for both pellets the system is controlled by mass transport when they are used as HER. However, in the case of HOR, the system is controlled by the electron transfer.
