Development of chemically modified electrodes as electro catalysts for oxygen reduction reaction

Abstract

The electrocatalytic reduction of oxygen by 1,4-naphthoquinone and some of newlineits derivatives at a bare glassy carbon electrode (GCE) and various modified glassy newlinecarbon electrodes has been investigated in the present study. For that, 1,4- newlinenaphthoquinone (NQ), 2-hydroxy-1,4-naphthoquinone (2-HyNQ), 5-hydroxy-1,4- newlinenaphthoquinone (5-HyNQ) and 2-amino-3-chloro-1,4-naphthoquinone (2-Am-3- newlineClNQ) were chosen as electrocatalysts. The modified glassy carbon electrodes were newlinefabricated by copper nanoparticles (CuNP), silver nanoparticles (AgNP), multiwalled newlinecarbon nanotubes (MWCNT), graphene oxide and multi-walled carbon newlinenanotube - graphene oxide hybrid materials (MWCNT-GO). newlineThe electrocatalytic ability of the modified electrodes for the reduction of newlineoxygen was examined by cyclic voltammetry, chronoamperometry and newlinechronocoulometry. The influence of pH and scan rate on voltammograms was newlinestudied. The surface characterization of the modified electrodes in the absence and newlinepresence of naphthoquinones was done using atomic force microscopy (AFM). The newlinestability and electrochemical behaviour of the modified electrodes were examined newlinein different buffer solutions of pH from 1.0 to 13.0 and neutral medium was found newlineto be the best medium to study the electrocatalysis by comparing the shift in oxygen newlinereduction potential and enhancement in peak current for reduction of oxygen. newlineThe diffusion coefficient values of naphthoquinones and the number of newlineelectrons involved in naphthoquinone and oxygen reduction were evaluated. There newlineis an involvement of two electrons in oxygen reduction reaction. Hence, the newlinereduction product is H2O2 which was confirmed by permanganate test. The newlinecombination of MWCNT-GO and naphthoquinones modified GCE exhibited the newlinemaximum shift in oxygen reduction potential. Hence, it can be used as oxygen newlinesensors. newline