Physical Chemistry Chemical Physics

doi: 10.1039/c0cp90129fpmid: N/A

doi: 10.1039/c0cp90131hpmid: N/A

doi: 10.1039/c0cp90128hpmid: 21046035

Méndez, Manuel A.; Partovi-Nia, Raheleh; Hatay, Imren; Su, Bin; Ge, PeiYu; Olaya, Astrid; Younan, Nathalie; Hojeij, Mohamad; Girault, Hubert H.

doi: 10.1039/c0cp00590hpmid: 20886142

The fundamental aspects of electrochemistry at liquid–liquid interfaces are introduced to present the concept of molecular electrocatalysis. Here, a molecular catalyst is adsorbed at the interface to promote a proton coupled electron transfer reaction such as hydrogen evolution or oxygen reduction using lipophilic electron donors.

Lim, Dong-Chan; Hwang, Chan-Cuk; Ganteför, Gerd; Kim, Young Dok

doi: 10.1039/c0cp00467gpmid: 20931113

In surface science, much effort has gone into obtaining a deeper understanding of the size-selectivity of nanocatalysts. In this article, electronic and chemical properties of various model catalysts consisting of Au are reported. Au supported by oxide surfaces becomes inert towards chemisorption and oxidation as the particle size became smaller than a critical size (2–3 nm). The inertness of these small Au nanoparticles is due to the electron-deficient nature of smaller Au nanoparticles, which is a result of metal-substrate charge transfer. Properties of Au clusters smaller than ∼20 atoms were shown to be non-scalable, i.e., every atom can drastically change the chemical properties of the clusters. Moreover, clusters with the same size can show dissimilar properties on various substrates. These recent endeavours show that the activity of a catalyst can be tuned by varying the substrate or by varying the cluster size on an atom-by-atom basis.

Ko, A-Ra; Kim, Jy-Yeon; Oh, Jae-Kyung; Kim, Hyun-Su; Lee, Young-Woo; Han, Sang-Beom; Park, Kyung-Won

doi: 10.1039/c0cp00394hpmid: 20820565

We report nanostructure electrodes for methanol electrooxidation by means of the co-sputtering deposition method. The Pt-WC-WO3 three-phase electrode has higher If/Ib and oxidation current density i.e. improved electrocatalytic activity in comparison with those of pure Pt and two-phase electrodes because of both catalysis of tungsten carbide and size-control by tungsten oxide.

Faisal, Shaikh Nayeem; Pereira, Carlos M.; Rho, Sangchul; Lee, Hye Jin

doi: 10.1039/c0cp00750apmid: 20924514

A new cost-effective amperometric proton selective sensor utilizing a single microhole interface between two immiscible electrolyte solutions (ITIES) is developed. The sensing methodology is based on measuring currents associated with proton transfer across the interface assisted by a proton selective ionophore. The ellipse shaped micro-interface was first fabricated by simple mechanical punching with a sharp needle on a thin PVC film (12 μm thick) commercially available as a food wrapping material. The microhole was then filled up with a gellified polyvinylchloride (PVC)-2-nitrophenyloctylether (NPOE) to create a single microhole liquid/liquid interface. Direct ion transfer reactions across the polarized interface serving as ion sensing platforms were studied using cyclic voltammetry. In order to enhance the selectivity of proton sensing, a proton selective ionophore, octadecyl isonicotinate (ETH1778), was incorporated into the organic gel layer and their electrochemical sensing characteristics were investigated using cyclic voltammetry and differential pulse stripping voltammetry. As an example, we employed the proton selective sensor for the determination of glucose concentrations. The detection scheme involves two steps: (i) protons are first generated by the oxidation of glucose with glucose oxidase in the aqueous phase; and (ii) the current associated with the proton transfer across the interface is then measured for correlating the concentration of glucose.

Ribeiro, José A.; Miranda, Inês M.; Silva, F.; Pereira, Carlos M.

doi: 10.1039/c0cp00751jpmid: 20882253

Interfaces between two immiscible electrolyte solutions are recognized as a simplified model for biological systems and they can be of great relevance to the characterization of biomolecules and their role in biological systems. In this work, ion transfer and facilitated ion transfer of protonated catecholamines (dopamine and noradrenaline) by dibenzo-18-crown-6 are investigated at the water/1,6-dichlorohexane interface. The formation constant of the complex between both dopamine and noradrenaline with dibenzo-18-crown-6 was evaluated and the experimental conditions for the analytical determination of those catecholamines are established. These results can improve the understanding of the pharmacodynamics of the catecholamines, and contribute to the study of their interaction with biological membranes. Furthermore it can be used to develop an alternative method for the determination of neural signal transmission catecholamines.

Sitta, Elton; Nascimento, Melke A.; Varela, Hamilton

doi: 10.1039/c002574gpmid: 20661518

Despite the fact that the majority of the catalytic electro-oxidation of small organic molecules presents oscillatory kinetics under certain conditions, there are few systematic studies concerning the influence of experimental parameters on the oscillatory dynamics. Of the studies available, most are devoted to C1 molecules and just some scattered data are available for C2 molecules. We present in this work a comprehensive study of the electro-oxidation of ethylene glycol on polycrystalline platinum surfaces and in alkaline media. The system was studied by means of electrochemical impedance spectroscopy, cyclic voltammetry, and chronoamperometry, and the impact of parameters such as applied current, ethylene glycol concentration, and temperature were investigated. As in the case of other parent systems, the instabilities in this system were associated with a hidden negative differential resistance, as identified by impedance data. Very rich and robust dynamics were observed, including the presence of harmonic and mixed mode oscillations and chaotic states, in some parameter region. Oscillation frequencies of about 16 Hz characterized the fastest oscillations ever reported for the electro-oxidation of small organic molecules. Those high frequencies were strongly influenced by the electrolyte pH and far less affected by the EG concentration. The system was regularly dependent on temperature under voltammetric conditions but rather independent within the oscillatory regime.

Ruvinskiy, Pavel S.; Bonnefont, Antoine; Bayati, Maryam; Savinova, Elena R.

doi: 10.1039/c0cp00593bpmid: 20830384

In this work we report on the influence of the catalytic layer architecture on the autocatalytic reaction of CO-bulk oxidation in liquid electrolyte by employing two types of nanomaterials: 2D arrays of Pt particles prepared on the surface of glassy carbon by colloidal lithography and 3D arrays of Pt nanoparticles supported on vertically aligned carbon nanofilaments. Oxidation of dissolved CO is studied experimentally using RDE approach and computationally using finite element method. For the first time, the influence of 3D architecture of the electrode on a complex bistable electrochemical system was investigated. The modelling results are in qualitative agreement with the experiment and explain the influence of nanostructure of the electrodes on such key characteristics of CO electrooxidation as the ignition potential, the width and the shape of the bistability region, and the value of the limiting current. Analysis of the experimental RDE curves suggests spontaneous formation of active and passive reaction zones along the fibre length which is supported by modelling.