Controlled Synthesis of Eutectic NiSe/Ni3Se2 Self‐Supported on Ni Foam: An Excellent Bifunctional Electrocatalyst for Overall Water Splitting

Abstract Here, the controlled synthesis of eutectic NiSe/Ni 3 Se 2 directly supported on Ni foam (NiSe/Ni 3 Se 2 /NF) is reported through a facile one‐pot hydrothermal method for the first time. The effects of reaction parameters on morphologies and corresponding electrochemical performances of NiSe/Ni 3 Se 2 /NF are investigated in detail. As a newfangled three‐dimensional bifunctional electrocatalyst, the electrocatalyst synthesized at 180 °C with 12 hours reaction time (denoted as NiSe/Ni 3 Se 2 /NF‐12) demonstrates the most regular morphology and best electrochemical properties. Benefiting from the synergistic effects between NiSe and Ni 3 Se 2 , and the large surface area of the highly conductive Ni foam, the novel 3D hybrid electrode provides predominant electrocatalytic performances towards both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline media. In addition, when used for full water splitting, NiSe/Ni 3 Se 2 /NF‐12 can drive a 10 mA cm ‐2 current density at ≈1.6V in 1 m KOH, which is competitive to the best electrocatalysts to our knowledge, with robust durability. Theoretical calculations confirm that the significant activity of the obtained material due to the unique 3D nanosheet architecture and interface reconstruction between NiSe and Ni 3 Se 2 through NiSe bonding, which results in the re‐distribution of charge and thus reduces the energy barrier of hydrogen desorption during the water decomposition.