Ternary MnO2/NiCo2O4/NF with hierarchical structure and synergistic interaction as efficient electrocatalysts for oxygen evolution reaction

Abstract

Ternary metal oxides MnO2/NiCo2O4 supported on nickel foam (NF) as electrocatalysts for oxygen evolution reaction (OER) have been fabricated via a two-step hydrothermal process. NF as support can provide excellent conductivity and 3 dimensional skeleton, which facilitate the utilization of active sites and mass transfer of electrolyte. The ternary MnO2/NiCo2O4/NF also possess the advantage of synergistic effect between MnO2 and NiCo2O4, implying the enhanced intrinsic activity for OER. XRD, EDX and XPS confirm the existence and distribution of each element of MnO2/NiCo2O4/NF. SEM shows the hierarchical structure of MnO2/NiCo2O4/NF with vertically aligned MnO2/NiCo2O4 nanoflakes covering on the surface of NF, which is in favor of the more exposed active sites and the fast dissipation of O2 bubbles. Additionally, to clearly testify the significance of the vertically aligned MnO2/NiCo2O4 nanoflakes, non-vertical MnO2/NiCo2O4/NF sample (MnO2/NiCo2O4/NF-1) is prepared for comparing OER performances in the same condition. OER measurements in alkaline solution show that ternary MnO2/NiCo2O4/NF displays better electrocatalytic activity with a low overpotential of 340 mV at a current density of 10 mA cm−2 than other samples. Therefore, ternary metal oxides with hierarchical structure on NF may be a promising choice for excellent electrocatalysts for OER.