C. Ponce-de-León

Copper deposition at segmented, reticulated vitreous carbon cathode in Hull cell

Abstract The electrodeposition of copper from an acid sulphate solution has been studied in a Hull cell fitted with four types of cathode; a carbon plate or a reticulated vitreous carbon (RVC) sheet was used either in a continuous or segmented form. The rates of mass transport to the planar plate and RVC electrodes have been compared in static and stirred electrolytes containing 50, 75 and 100 mmol dm–3 CuSO4 in 0·5 mol dm–3 Na2SO4 at pH 2 and 298 K. The cathodes were divided into 10 equal sections and current vs. potential curves were obtained for each section at a constant current up to 140 mA. The current distribution over the cathodes followed a logarithmic decay with distance along the cathode; segments nearest to the anode experienced the highest rate of copper deposition.

Multihierarchical electrodes based on titanate nanotubes and zinc oxide nanorods for photoelectrochemical water splitting

Studies involving water splitting to form hydrogen and oxygen have attracted attention because H2 is considered the fuel of the future. Photoelectrocatalysts have been widely used for this application, and several metal oxides can be applied as catalysts. Among them, we highlight zinc oxide nanorods (ZnONRs) and titanate nanotubes (TiNTs); however, their individual nanostructures exhibit disadvantages. For example, ZnONRs show rapid recombination of the photogenerated charges, and TiNTs give rise to randomly oriented films; these disadvantages limit their application as photoanodes. In this study, for the first time, we present a new class of multihierarchical electrodes based on TiNT-decorated ZnONR films that exhibited superior results to the individual species. The TiNTs are homogenously dispersed over the surface of the rods without forming agglomerates, giving rise to a heterojunction that exhibits lower recombination rates. It was found that the results are better when the contents of TiNTs in the electrode are higher; thus, glycine was successfully used as a bridge to link both of the structures, increasing the amount of TiNTs decorating the rods. As a result, the photocurrent generated with these multihierarchical electrodes is higher than that obtained with pure ZnONR electrodes (0.9 mA cm−2 and 0.45 mA cm−2 at 1.23 VRHE, respectively), and the electrode potentials for O2 evolution are lower than those observed for pure TiNT electrodes (0 V and 0.8 V vs. ERHE, respectively). The IPCE values are also higher for the multihierarchical electrodes.

Platinum-free lead dioxide electrode for electrooxidation of organic compounds

As electrode material, PbO2 coatings are inexpensive and easy to manufacture by anodic deposition. Moreover, they present low resistivity and, due to their high efficiency in organic oxidation reactions, they continue to attract interest as an object of study and of application in the electrochemical treatment of effluents. During preparation of the electrode, a thin Pt layer is usually deposited on the Ti substrate before receiving the PbO2 layer in order to prevent the formation of TiO2 on the substrate surface, thereby ensuring adhesion of the coating. In this study, PbO2 layers were deposited on a Ti substrate, using Pb as interlayer in place of Pt. Aiming for a cheaper and faster-to-prepare electrode, the Pb interlayer was reduced from a Pb(NO3)2 solution on Ti and then, by reversing the potential in the same electrolyte, PbO2 was anodically deposited. The Ti/Pt/PbO2 and Ti/Pb/PbO2 electrodes were characterized comparatively by cyclic voltammetry in the potential region where the solid state surface redox transitions (SSSRT) take place. Capacitive currents were compared as well as the roughness factor being the Ti/Pb/PbO2 electrode rougher, with higher surface area. As a consequence, it showed better performance in the color electro-removal of a Remazol Black azo dye solution.