Hierarchical Fe-Mn binary metal oxide core-shell nano-polyhedron as a bifunctional electrocatalyst for efficient...

Electrochemical water splitting is convinced as one of the most promising solutions to combat the energy crisis. The exploitation of efficient hydrogen and oxygen evolution reaction (HER/OER) bifunctional electrocatalysts is undoubtedly a vital spark yet challenging for imperative green sustainable energy. Herein, through introducing a simple pH regulated redox reaction into a tractable hydrothermal procedure, a hierarchical Fe₃O₄@MnO binary metal oxide core-shell nano-polyhedron was designed by evolving MnO wrapped Fe₃O₄. The MnO effectively prevents the agglomeration and surface oxidation of Fe₃O₄ nano-particles and increases the electrochemically active sites. Benefiting from the generous active sites and synergistic effects of Fe₃O₄ and MnO, the Fe₃O₄@MnO-NF nanocomposite implements efficient HER/OER bifunctional electrocatalytic performance and overall water splitting. As a result, hierarchical Fe₃O₄@MnO only requires a low HER/OER overpotential of 242/188 mV to deliver 10 mA cm^-2, a small Tafel slope of 116.4/77.6 mV dec^-1, combining a long-term cyclability of 5 h. Impressively, by applying Fe₃O₄@MnO as an independent cathode and anode, the overall water splitting cell supplies a competitive voltage of 1.64 V to achieve 10 mA cm^-2 and super long cyclability of 80 h. These results reveal that this material is a promising candidate for practical water electrolysis application.