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It is of great importance to construct non-precious metal bifunctional electrocatalysts with low cost and high efficiency for overall water splitting. In this work, a nickel foam (NF) supported hierarchical MnCo2O4 nanowire@NiFe layered double hydroxide (LDH) heterostructure (labeled as MCO@NiFe-LDH/NF) was constructed using a hydrothermal-annealing-hydrothermal route. Electrochemical tests showed that the as-constructed MCO@NiFe-LDH/NF could be used as an integral electrode for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1 M KOH electrolyte. To get the current density of −10 mA cm−2 for HER or 100 mA cm−2 for OER, an overpotential of 129/283 mV was separately required. In a two-electrode system with MCO@NiFe-LDH/NF as both the anode and cathode, 1.55/1.705 V of cell voltage was needed to reach current density of 10/100 mA cm−2. More importantly, the as-constructed integral electrode could continuously catalyze for 200 h, full water splitting at the current density of 50 mA cm−2, demonstrating prominent long-term stability. [ABSTRACT FROM AUTHOR]

FeNi-layered double hydroxide (LDH) is thought to be an excellent electrocatalyst for oxygen evolution reaction (OER) but it always shows extremely poor electrocatalytic activity toward hydrogen evolution reaction (HER) in alkaline media. Hence, it is significant to improve its HER activity to make it a bifunctional electrocatalyst for the decomposition of water. Here, a simple galvanostatic electrodeposition method was designed for the successful construction of the bifunctional FeNi3@FeNi LDH electrocatalyst. The as-prepared catalyst displayed excellent electrocatalytic activity for HER/OER in 1.0 M KOH. To drive the current density of 10 mA cm−2 for HER/OER, an overpotential of 106/199 mV was needed, respectively. In a two-electrode system with the FeNi3@FeNi LDH/NF as the anode and the cathode simultaneously, the overpotential hardly changed after continuously working for 168 h at 10 mA cm−2. Compared with other FeNi-based catalysts, the present catalyst possessed close or better electrocatalytic activity. [ABSTRACT FROM AUTHOR]