An Electrochemical Investigation of Methanol Oxidation on Thin Films of Nickel Oxide and Its Composites with Zirconium and Yttrium Oxides

Abstract

The present work is focused on the fabrication of NiO-ZrO2 /FTO and NiO-Y2 O3 /FTO thin films via a simple dip-coating method. The films are deposited from precursor solutions of Ni(CH3 COO)2·2H2 O, Zr(CH3 COO)4, Y(CH3 COO)3·H2 O in methanol. The synthesized films, after proper characterization, are employed for electrochemical oxidation of methanol. The analytical techniques such as X-ray diffraction (XRD), Raman, and Infrared (IR) spectroscopy reveal the suc-cessful formation of crystalline thin films of mixed metal oxide without any additional impurities. Further, X-ray photoelectron spectroscopy (XPS) results, confirm the composition and oxidation state of all the elements present in thin films. The field emission scanning electron microscopy (FESEM) further aided to identify the uniformity and porous nature of composite thin films while the energy-dispersive X-ray spectroscopy (EDS) confirms the targeted elemental composition of the prepared thin films is in good agreement with precursors. The electrochemical oxidation of methanol results reveals that NiO-Y2 O3 /FTO and NiO-ZrO2 /FTO thin films showed current densities of 6.2 mA/cm2 and 10 mA/cm2 at 0.65 V, respectively, against Ag/AgCl/3M KCl using 0.6 M methanol solution. Furthermore, Chronoamperometric (CA) results show good stability of NiO-ZrO2 /FTO and NiO-Y2 O3 /FTO thin films with observed current decay of 10% and 6.8% of the initial current density, respectively. Moreover, the effect of scan rate and concentration of metals in a catalyst was also investigated. The Electrochemical impedance studies (EIS) further support electrochemical results, where the lower charge transfer resistance (Rct ) values are recorded for composite thin films as compared to the pure metal oxide thin films (NiO/FTO, ZrO2 /FTO, and Y2 O3 /FTO).