This is a comprehensive review of the electrochemical synthesis of nano/microstructure transition metal-based materials for oxygen evolution reaction from the aspects of ‘Fundamentals, Structural design and Classification’.

No abstract

No abstract

NiFe layered double hydroxides (NiFe-LDHs) are considered as a promising substitute for noble metal electrocatalysts for oxygen evolution reactions (OER). A three-dimensional NiFe layered double hydroxides nanowire/nanoporous Ni interlayer/nickel foam substrate (NiFe-LDH/Ni/NF) electrocatalyst was designed and prepared on NF by a polystyrene (PS) microsphere template and a two-step in situ electrodeposition method. The electrocatalysts had a high specific surface area, an increased number of electrocatalytic active sites and improved electrochemical stability. In NiFe-LDHs/Ni/NF, the nickel nanoporous interlayer bonded closely with the NF matrix and simultaneously became loaded with the NiFe-LDH nanowires, which accelerated the electron transfer of the electrocatalyst nanowires to the matrix, increased the apparent active area, and promoted the OER. As expected, with a current density of 10 mA cm −2 , NiFe-LDHs/Ni/NF exhibited a smaller overpotential of 247 mV, a smaller Tafel slope of 35.52 mV dec −1 and better durability than those of Ni/NF or NiFe-LDHs/NF. In addition, the overall water splitting system with the anode of NiFe-LDHs/Ni/NF and the cathode of Ni/NF had a small potential of 1.55 V with a current density of 10 mA cm −2 .

Amorphous FeOOH nanosheets were electrodeposited onto nickel foam (NF)-supported NiCo2S4 nanotube arrays to form a three-dimensional FeOOH@NiCo2S4/NF core-shell heterostructure, which is a bifunctional electrocatalyst for overall water splitting (OWS). FeOOH@NiCo2S4/NF pre-catalyst showed a good electrocatalytic activity and stability for the oxygen evolution reaction in a 1 M KOH solution, with an overpotential of 228 mV at 10 mA cm−2, a Tafel slope of 44.03 mV dec−1 and a durability of more than 50 h. The overpotential of the hydrogen evolution reaction was 112 mV at 10 mA cm−2. The OWS performance was very good because it only required a voltage of 1.56 V at 10 mA cm−2. The 3D core-shell structure with a large electrolyte contact interface, the good electronic conductivity, the large surface exposure of active sites by the NiCo2S4 nanotube arrays, and the strong electron interaction at the heterogeneous interface between FeOOH and NiCo2S4 are the key factors for the excellent performance.