1,721,014 research outputs found
Recent developments in understanding factors of electrocatalysis
No full textAfter an introductory analysis of terms and concepts in the field of electrocatalysis, a number of experimental examples are reported to illustrate various factors. In particular, Tafel slope and PZC of oxide electrodes are shown to be able to disentangle electronic from geometric factors. The points under discussion are: effect of particle size and methods of preparation, surface vs. bulk composition, primary vs. secondary effects with redox systems depending on the molecular structure of the couple, single crystal vs. polycrystalline surfaces. The last case is particularly relevant since for the first time "vicinal" faces of RuO2 are shown to behave at the extremes of the usually observed experimental picture
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Surface and electrocatalytic properties of well-defined and vicinal RuO2 single crystal faces
No full textThe kinetics of Cl-2 evolution from concentrated NaCl solutions on the (110) and (230) faces of RuO2 single crystals has been investigated by determining the Tafel slope, the stoichiometric number and the reaction orders with respect to Cl- and H+. The experimental parameters suggest that the mechanism is presumably similar to that put forward earlier by Krishtalik [51] for RuO2 layers, but a step common to oxygen evolution, like the case of polycrystalline samples, is present only with the (230) face. Reasons for this difference and for the apparent lower activity of the (110) face with respect to the (230) are discussed. A detailed analysis of the surface behavior of the two faces in Cl- free acid and alkaline solutions has also been carried out by cyclic voltammetry
Oxygen evolution on aged IrOx/Ti electrodes in alkaline solutions
No full textO2 evolution from 1 mol dm−1 NaOH aqueous solution was studied on IrO x /Ti electrodes already used for more than 3 years (aged). IrO x was prepared by thermal decomposition of the chloride in the temperature range from 330 to 500 °C. Half of the electrodes were stored in air between experiments, the other half in water. The state of the electrode surface was monitored by recording voltammetric curves in a potential region prior to O2 evolution before and after each group of experiments. O2 evolution was studied by measuring quasistationary current–potential curves. Tafel slopes were derived using two different approaches. The reaction order with respect to OH− was also determined and found to be fractional. Results show that the reaction mechanism does not depend on either the calcination temperature or the storage conditions. However, stability appears to be higher for electrodes calcined at higher temperatures and stored in air
Surface modification of RuO2 electrodes by laser irradiation and ion implantation: Evidence of electrocatalytic effects
No full textRuO2 thin layers were deposited on Ti supports by thermal decomposition of RuCl3 at 400°C. Some of the samples were subjected to laser irradiation between 0-5 and 1-5 J cm-2. Some others to Kr bombardment with doses between 1015 and 1016 cm-2. Modifications introduced by the surface treatments were monitored by cyclic voltammetry and O2 evolution in H 2SO4 solution. The voltammetric charge increased with surface treatment almost to the same extent for irradiation and bombardment. The electro-catalytic activity turned out much higher for Kr bombarded samples. Raw experimental data were scrutinized in an attempt to separate geometric from electronic factors. True electrocatalytic effects are clearly seen to prevail over purely surface area effects
Relation of anodic and cathodic performance to pH variations in membraneless microbial fuel cells
No full textOne-compartment (membraneless) microbial fuel cells (MFCs) are effective tools to test new bio-technology at a laboratory level. More efforts in MFC design and materials are necessary to move from laboratory tests to real applications.
In such a context, this paper presents the experimental results that investigate pH variations of three single chamber and membraneless MFCs having positive and negative electrodes made of graphite-based materials without any addition of chemical catalysts. MFCs were built and operated with raw wastewater (inoculum) and sodium acetate as substrate. The progression of the power in the MFC and the relationship between performances and induced pH variation (from pH 6.7 to 10.2) will be discussed. A general connection between SEM images, chemical analyses, pH trends and reactions in the MFCs will be attempted, by connecting all processes with thermodynamic and chemical equilibria considerations
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