Strong Catalytic Effect of Cobalt Oxide Nanoparticles on the Electrochemical Sensing of Arsenic

BARBERO C. A.; RUSBEL CONEO RODRÍGUEZ; ACEVEDO D. F.; PLANES G. A.

Saint Malo

Congreso; 17th Topical Meeting of the International Society of Electrochemistry Multiscale Analysis of Electrochemical Systems; 2015

International Society of Electrochemistry

Modified electrodes can be used for the electrochemical sensing of contaminant in aqueous environment. The usual modified electrode is made by covering a conducting material (e.g. glassy carbon) with a thin film of and catalytic layer. While cyclic voltammetry allows to qualitatively evaluating the catalytic effect of the layer, a quantitative analysis requires controlled mass transfer such that obtained using rotating disk electrodes. Besides thin films, solid nanoparticles could be used as catalytic material for sensing contaminants. In that sense, so called ?electrocatalytic? effects have been observed for electrodes modified with nanoparticles (e.g. carbon nanotubes). However, it has been shown that diffusion effects in the nanoparticle layer could be mistaken for changes in charge transfer rates.[1] Similar effects have been observed with porous electrodes.[2] Recently, a quantitative model for the surface catalysis of nanoparticles modified electrodes, which take into account mass transfer effects have been proposed by Compton and coworkers.[3] In the present communication we measure both cyclic voltammetry (CV) and rotating disk voltammetry (RDV) of arsenite oxidation on glassy carbon electrodes modified with cobalt oxide nanoparticles. The nanoparticles were deposited by cyclic voltammetry of the base electrode in cobalt (II) solution,[4] allowing to control the amount of material deposited on the surface. The redox properties of the cobalt oxide nanoparticles are measured by cyclic voltammetry while the ion exchange is measured by Probe Beam Deflection (PBD).[4] Both CV and RDV show a strong effect of the amount of nanoparticles on the apparent overpotential for arsenite oxidation. The model proposed by Compton and coworkers,[3] is modified assuming that the cobalt oxide nanoparticles acts as volumetric redox catalysts and not only as surface catalysts. The effective charge transfer constant shifts with the amount of nanoparticles in a way that corresponds to the modified model. The relevance of the data for the design of electrochemical sensors for arsenic species is discussed.