Improving the electrochemistry and microstructure of nickel electrode by deposition on anodized titanium substrate for the electrocatalytic oxidation of methanol and ethanol

Abstract

The electrodeposition process of nickel and the substrate used for the electrodeposition can be improved to obtain an effective catalyst for methanol oxidation. Thus, nanoparticles of nickel have been uniformly electrodeposited on the surface of previously anodized titanium at 5 V during 1 h. The optimized microstructure has been studied by using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The XPS and argon-ion etching experiments have revealed the composition profile of the titanium/titania/nickel thin film electrode. Metallic Ni is detected by XRD. The nickel particles dispersed in a porous TiO₂ substrate have great catalytic activity for methanol oxidation in basic solution and through the redox couple NiO(OH)/Ni(OH)₂. The optimized titania substrate yields to electrodes (crystalline titanium/amorphous titania/nanocrystalline nickel) with higher catalytic activity than non-anodized metallic titanium (titanium/nickel). However, further oxidation and thickening of the titania film drives to poorer electrochemical behavior. The SEM and EDS results show that the nickel particles exhibit certain tendency to agglomerate and to form spherical particles of around 2 μm. This electrode material also is active to oxidize ethanol, but this activity is poorer.