Use of urchin-like NixCo3−xO4 hierarchical nanostructures based on non-precious metals as bifunctional electrocatalysts for anion-exchange membrane alkaline alcohol fuel cells

Abstract

Bifunctional electrocatalysts based on non-precious metals were developed for the dioxygen reduction and methanol oxidation reactions. These electrocatalysts can be considered as candidate cathode and anode materials for anion-exchange membrane (AEM) alkaline alcohol fuel cells. A series of Ni-doped cobalt oxide (Ni_xCo_3−xO₄) hierarchical nanostructures composed of one-dimensional nanorods was prepared by an inexpensive hydrothermal method. X-ray diffraction patterns showed that the Ni_xCo_3−xO₄ crystallized in a cubic spinel phase. The electrochemical performance of the catalysts was investigated using a conventional cyclic voltammetry technique. The electrocatalytic behaviour of the Ni_xCo_3−xO₄ hierarchical nanostructures was compared with the behaviour of Co₃O₄ and Co_0.33Ni_0.67O. The synergistic behaviour of the Ni in the Ni_xCo_3−xO₄ nanostructures was established with respect to the Ni content. Ni_xCo_3−xO₄ hierarchical nanostructures show a better catalytic behaviour than Co₃O₄ and Co_0.33Ni_0.67O. Although the Ni_xCo_3−xO₄ compositions all showed good catalytic behaviour, Ni₁Co₂O₄ was identified as a superior bifunctional electrocatalyst for the oxygen reduction and methanol oxidation reactions in alkaline media. The effect of the Ni content on the electrocatalytic properties of the Ni_xCo_3−xO₄ hierarchical nanostructures was clearly shown. The use of these electrocatalysts based on non-precious metals could have a commercial impact on the development of non-platinum electrocatalysts for application in AEM alkaline alcohol fuel cells.