Oxygen Evolution Reaction On Nano Transition Metal Oxide

Nanowire arrays of mixed oxides of Co and Ni freely standing on Ni foam wasprepared by template-free method. The effects of Ni content on the morphology, structureand catalyst performance for oxygen evolution reaction were investigated by scanningelectron microscopy, X-ray diffraction spectroscopy and electrochemical techniquesincluding cyclic voltammetry, chronopotentiometry and electrochemical impedancespectroscopy. A transformation from nanowire arrays to nanoplate arrays was found withthe increase of the atomic ratio of Ni to Co in the preparation solution. The Ni_xCo_3-xO₄electrode obtained at1:1of Ni:Co in the preparation solution has nanowires array structureand exhibits better catalytic performance for oxygen evolution reaction than otherNi_xCo_3-xO₄and Co₃O₄electrode. The catalytic activity of the Ni_xCo_3-xO₄and Co₃O₄electrode is correlated with their surface roughness. Superior stability of Ni_xCo_3-xO₄nanowire array electrode was demonstrated by chronopotentiometric test. The reactionorders with respect to OH-on Ni_xCo_3-xO₄electrode at low overpotential is close to2.0atlow overpotentials and1.0at high overpotentials.FeOOH nanowires were prepared and characterized with X-ray diffractionspectroscopy and scanning electron microscopy. A composite electrode consisting ofFeOOH and Ni foam （FeOOH/Ni-foam） was fabricated and its catalytic performance foroxygen evolution reaction （OER） was evaluated and compared with nanowireNiCo2O4/Ni-foam electrode. The mass current density of OER on FeOOH/Ni-foam isaround3times of that on NiCo2O4/Ni-foam. Ni foam played a key role for the high activityof the FeOOH/Ni-foam. A synergistic mechanism of FeOOH and Ni was proposed toaccount for the superior catalytic performance of the FeOOH/Ni-foam electrode. Themechanism was verified by Fe₃O₄/Ni-foam electrode. The electrocatalytic performance ofFeOOH nanowires freely standing on nickel foam for OER is better than theircorresponding teflon-bond FeOOH/Ni-foam electrodes. The reaction orders with respect toOH-on FeOOH/Ni-foam electrode at low overpotential is close to1.5at low overpotentialsand2.0at high overpotentials.