Enhanced Methanol Oxidation in Alkaline Media on Electrodeposited Ni Electrodes by Morphological and Crystallographic Evolution

Abstract

This research aims at exploiting the electrocatalytic behaviour of nano-crystalline nickel electrodes electrodeposited by different techniques including direct current (DC), pulse current (PC), or pulse reversal current (PRC) for methanol electrooxidation in alkaline solutions. We understand that PC electrodeposition forms pyramidal shaped grains with a preferential Bragg diffraction peak of (111), whereas PRC produced refined spherical grain morphology with a strong (200) diffraction peak. However, DC electrodeposition exhibits an intermediate morphology and crystalline structure. Cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) show that PRC electrodeposition develops Ni electrodes with better electrocatalytic activity for methanol electrooxidation than other two nickel electrodes. Based on the CV curve, the current density for Ni prepared by PRC electrodeposition methods is about 75.26 mA.cm−2, which is higher than those of DC and PC methods. This higher activity of PRC electrodeposited nickel is attributed to the low charge transfer resistance confirmed by Nyquist plots. We attributed this behavior to the (200)-oriented crystallographic texture, spherical grain morphology, and consequently the high electrochemical active surface area of this nickel electrode. This work reveals the importance of surface morphology and crystallography on the electrocatalytic behaviour of nickel electrodes for electrochemical energy devices.