The influence of cobalt loading on electrocatalytic performance toward glucose oxidation of pillared montmorillonite-supported cobalt

Abstract

• Aluminum-pillared clays with different cobalt loadings were synthesized. • Modified carbon paste electrodes were tested in glucose electrooxidation. • Increase in Co loading (up to 4.13 wt%) enhanced the electrocatalytic performance. • Further increase in Co loading derogated the electrocatalytic performance. • Co 3 O 4 formation probably altered the electrocatalytic performance. In this paper, the influence of cobalt loading in pillared clay-supported cobalt materials on their electrocatalytic performance toward glucose oxidation was investigated. A series of aluminum-pillared montmorillonite clay (AP) materials with different cobalt loadings (x%CoAP, x = 1, 3, 5, and 10 wt%) was synthesized using the incipient wetness impregnation method. The X-ray powder diffraction (XRPD), inductively coupled plasma optical emission spectroscopy (ICP-OES), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy coupled with energy dispersive X-ray spectrometry (FE-SEM/EDX), high resolution transmission electron microscopy (HR-TEM) coupled with EDX, X-ray photoelectron spectroscopy (XPS), and low temperature N 2 physisorption, were employed for characterization of the materials. The incorporation of cobalt in porous structure of pillared montmorillonite was confirmed. The synthesized materials (x%CoAP) were used for modification of carbon paste (CP) electrode and tested in reaction of glucose electrooxidation. The electrochemical measurements were conducted using cyclic voltammetry and chronoamperometry in a 1 M NaOH solution, with or without glucose. The results showed that the increase of cobalt loading improved the electrode performance toward glucose. The highest current response and sensitivity were obtained for the CP-5%CoAP electrode. A lower electrode performance of CP-10%CoAP was correlated with the presence of higher quantities of Co 3 O 4 (confirmed by XRPD and XPS) in the electrode material. The mechanism and kinetics of glucose electrooxidation was studied in more details for the best performing electrode (CP-5%CoAP). It was found that the process was diffusion-controlled and the diffusion coefficient was determined. The charge transfer coefficient and catalytic rate constant were calculated. The electrode exhibited satisfactory repeatability, reproducibility, stability, and selectivity. The obtained results showed that appropriate amount of cobalt loading in pillared clay led to the obtainment of non-enzymatic electrode materials suitable for sustainable and green glucose sensors.