The extremely low sample volumes required for capillary electrophoresis and the high sensitivity and selectivity of electrochemical detection make capillary electrophoresis/electrochemistry (CEEC) a very useful method for bioanalysis. In this paper, two types of dual-electrode detectors for CEEC are described. The first employs a ring-disk microelectrode placed in a wall-jet configuration and is used for the selective detection of substances undergoing chemically reversible oxidations. Collection efficiencies obtained for catecholamines with this configuration were between 25 and 35%. The second electrode design consists of two adjacent carbon fibers embedded in an epoxy matrix and is analogous to the parallel dual-electrode configuration used in liquid chromatography/electrochemistry. This configuration can be used to confirm peak identity and purity by operating the electrodes at two different potentials. Alternatively, it is possible to perform simultaneous oxidative and reductive electrochemical detection.

Carbon fiber disk ultramicroelectrodes (UMEs) with well-defined geometries were prepared by chemical vapor deposition techniques. Transparent silica films with thicknesses from 1 to 600 microns were deposited on the cylindrical length of 5 and 10 microns carbon fibers from a SiCl4, H2, and O2 ternary precursor system at 850-1150 degrees C or sequential deposition from Si(OEt)4 as a single source precursor at 700 degrees C followed by the SiCl4, H2, and O2 precursor system. Film thickness, film adhesion to the fiber substrate, and the overall dimensions of the silica-coated carbon fiber were studied and found to be a function of the precursor system, precursor concentrations, fiber diameter, deposition time, and fiber temperature. The silica films were found to be free of microcracks and characterized by a quality seal between the carbon fiber and the coating. As a result, the silica-coated disk UME exhibits an excellent electrochemical response without the need to use an epoxy sealant at the electrode tip. Furthermore, the deposition of hard and inert ceramic materials imparts durability to fragile carbon fibers and facilitates the handling of UMEs in microenvironments. Finally, the advantage of concentric deposition about the fibers to produce a disk UME in the center of an insulating plane was used to examine the effect of the thickness of the insulating coating on the limiting current response.

No abstract

Developing earth abundant catalysts for clean energy technologies is vital to address the issues related to the use of fossil fuels and associated pollution, which adversely affects human health. Herein, we report an electrochemically deposited mixed Cu−Co−P film, as a bifunctional catalyst with high stability and activity for the hydrogen evolution reaction (HER, in 0.5 M H 2 SO 4 and 1 M KOH) and the oxygen evolution reaction (OER, in 1 M KOH). In alkaline medium, the Cu−Co− P catalyst outperforms the state-of-art catalysts for both HER (Pt) and OER (RuO 2 ) and is stable under continuous electrolysis for up to 72 hours. Using Cu−Co−P electrodes as both the anode and the cathode increases the activity by ∼2.5 times greater than the integrated performance of RuO 2 (anode) and Pt (cathode) at 1.9 V. The competent bifunctionality of Cu−Co−P is facilitated by Cu incorporation, leading to a low surface passivation of the electrode. This study offers a new strategy to develop earth abundant bimetallic phosphides, which are potential catalysts for many alternative energy technologies.

No abstract