Fabrication and Electrocatalytic Properties of Metal Oxide – Metal Oxide Hybrids

Abstract

The primary objective of the present study was to exploit unusual and potentially unique properties of metal oxide coated metal oxide nanomaterials which were synthesized in two stages by adopting simple route. Five metal oxides: MgO, Al 2 O 3 , Fe 2 O 3 and CeO 2 were selected as substrate materials and prepared by simple precipitation method (except TiO 2 ). CuO was chosen as an active component and was loaded onto each substrate by impregnation technique. Five loads of CuO in 5, 10, 15, 20, 25 wt% compositions onto various substrates were prepared. The prepared nanomaterials were characterized by Fourier transform infrared spectroscopy (FT-IR), X-Ray diffraction (XRD), scanning electron microscopy (SEM) along with EDX analysis, transmission electron microscopy (TEM), particle size distribution (PSD) and BET-analysis. Glassy carbon electrode (A = 0.07 cm 2 ) was modified with each catalyst by drop-casting and used for investigating electrochemical behaviour in neutral (KCl), basic (KOH), acidic (H 2 SO 4 ) and PBS buffer solutions. Electrochemical studies on the prepared electrodes were done through electrochemical impedance spectroscopy (EIS) which revealed the conductive properties of synthesized hybrid nanomaterials and thus the electrocatalytically active ratio of CuO on respective substrates was assessed. 15CuO@MgO, 20CuO@Al 2 O 3 , 5CuO@TiO 2 , 10CuO@Fe 2 O 3 and 10CuO@CeO 2 presented better conductive properties in their respective series. Cyclic voltammetry (CV) was carried out to elucidate the redox behavior of these electroactive materials in H 2 SO 4 . Peak current-voltage (CV) responses of the modified electrodes in each hybrid catalyst series were in linearity with the CuO composition. Quantification of CuO in the respective catalysts was thus also made possible by using CV data in this technique. In order to explore the diverse role and investigate applications as potential electrocatalysts; electroxidation of two model analytes was carried out on all of the electrodes modified with the active hybrid materials. All the electrodes showed the potential to electrocatalyze glucose and methanol in alkaline media, however as predicted vis EIS studies; one optimal composition projected enhanced performance in each series; 20CuO@Al 2 O 3 , 5CuO@TiO 2 , ii10CuO@Fe 2 O 3 and 10CuO@CeO 2 . In CuO coated MgO series, 15CuO@MgO presented better electrocatalytic responses for ascorbic acid sensing in phosphate buffer solution at pH 7.4. This study scheme can be promoted for the electrochemical sensing of the biologically important analytes using the hybrid nanomaterials and also for the electrocatalysis applications. The synthesized nanomaterials possess potentiality for the future sensing and electrocatalysis smart technologies.