Anodic Pretreatment of Glassy Carbon: Impacts on Structural and Electrochemical Characteristics of Niox Nanoparticles

Abstract

Usually, glassy carbon electrode (GC) is used as it is as a substrate for electrochemically deposited nickel or nickel oxide (NiOx) nanoparticles. In the present study, GC carbon is anodically oxidized in different media prior to electrode position of NiOx and the impacts of this pretreatment on the structural and electrochemical characteristics of NiOx are studied. Upon anodic pretreatment of GC electrode in acid (0.1 M H2SO4, GCOX-AC) and in alkali (0.1 M NaOH, GCOX-AL), the structural and electrochemical characterizations of nickel oxide (NiOx) nanoparticles are highly modified. Cyclic voltammetry (CV), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) are used for characterization of the electrodes. While NiOx nanoparticles deposited on GCOX-AC reveal a bird-like shape, it shows semi-spherical shape when it is deposited on either GC or GCOX-AL, with smaller size on the GCOX-AL. The reversibility of the Ni(OH)2/NiOOH couple increases at both GCOX-AC/NiOx and GCOX-AL/NiOx compared to the untreated case, GC/NiOx. The enhancement in the electrocatalytic properties of both GCOX-AC/NiOx and GCOX-AL/NiOx was tested by glucose oxidation in alkaline solution. Peak current for glucose oxidation on the modified electrodes shows linear behavior according to the trend theoretically depicted by Randles-Sevcik equation for completely irreversible diffusion-controlled process. The enhancement in the catalytic activity of both GCOX-AC/NiOx and GCOX-AL/NiOx is discussed in the light of surface analysis of both electrodes compared to the untreated GC (i.e., GC/NiOx).