Fabrication and characterization of Ni modified TiO2 electrode as anode material for direct methanol fuel cell

Abstract

Highly ordered porous titanium dioxide nanotube (TiO2-NT) surfaces were prepared with anodization method to obtain a larger specific surface area that plays a very important role in methanol oxidation. In this regard, optimum conditions such as various anodization voltages and times were determined. The largest surface area of TiO2 occurred at anodization voltage and time of 60 V and 2 h, respectively. After obtaining the high specific surface area, very small amounts of Nickel (Ni) nanoparticles were deposited on TiO2-NT surface and their behaviors of methanol electro-oxidation were investigated by Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronoamperometry (CA) methods. Characterizations of the TiO2-NT and Ni modified electrodes are exerted by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). The average tube length and diameter are 36.32 mu m and 93.6 nm according to SEM images. XRD results indicated the tetragonal structured anatase of TiO2 and Ni (111) and (200). While methanol oxidation peak does not observe on TiO2-NT surface, behaviors of methanol oxidation depend on the Ni content on TiO2-NT surface. Oxidation response increases by the increasing amount of Ni nano-particles in the deposits. High surface coverage (Gamma) with 3.87 x 10(-9) mol cm(-2) and very low activation energy (E-a) with 11.0 kJ/mol are measured on Ni modified TiO2-NT with the highest Ni content. Charge transfer resistance either reduced or provided long stability and durability with the deposition of Ni on TiO2-NT. This may associate that TiO2-NTs with the large surface areas may play a significant role in the methanol oxidation efficiency. Modification of TiO2-NT surface with Ni particles is an effective plan for high-performance electrocatalysis. Besides, the strong electronic interaction between Ni and TiO2 may facilitate the adsorption of methanol through the bi-functional mechanism on the electrode surface. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.