Standalone nickel layered double hydroxide and nickel oxide electrodes as effective anodes in alkaline direct methanol fuel cell

Abstract

Direct methanol fuel cell is an emerging energy transformation system with the prospect of substituting secondary batteries soon due to their exciting features. One of the most limitations is the weak catalytic activity of the expensive nonprecious Pt-based catalysts at the fuel cell's anode. In this work, a standalone Nickel layered double hydroxide of hierarchical nanosheet structure was effectively synthesized on the nickel foam's surface through facile hydrothermal treatment that subsequently converted into NiO without destroying the structure by heat treatment at 500 °C. The synthesized standalone electrodes demonstrated a significant activity for methanol oxidation with an onset potential of 0.35 V in KOH (1 M), which is attributed to the Ni(OH)2 (Ni+2)/(Ni+3) NiOOH active site. The electrodes effectively discharged current at 0.5 V for more than 1 h with no performance degradation compared to the bare nickel foam. The better activity of the synthesized electrodes was attributed to the nanosheet structure layer's better charge and mass transfers, as confirmed by the morphological images (SEM images) and the electrochemical characteristics (electrochemical impedance spectroscopy, chronoamperometry, and cyclic voltammetry).