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/Ni3Se2 directly supported on Ni foam (NiSe/Ni3Se2/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/Ni3Se2/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/Ni3Se2/NF‐12) demonstrates the most regular morphology and best electrochemical properties. Benefiting from the synergistic effects between NiSe and Ni3Se2, 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/Ni3Se2/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 Ni3Se2 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.

Regulating Phase Conversion from Ni3Se2 into NiSe in a Bifunctional Electrocatalyst for Overall Water‐Splitting Enhancement

“…This approach reminds us of the necessity to construct phase junctions in electrocatalysts with high surface area and greater contact areas with reactants during the catalytic process. Phase conversion has been demonstrated as an efficient method for the enhancement of the electroconductivity of catalysts and yield more active sites due to the atom rearrangement in the phase transformation . Moreover, phase junctions, consisting of the intermediate states in the conversion of the phases, not only synergistically reduces the chemisorption‐free energies of H + and OH − but also facilitates the separation of the intermediates on different interfacial sites, thus, enhancing both HER and OER .…”

Water‐Induced Formation of Ni2P–Ni12P5 Interfaces with Superior Electrocatalytic Activity toward Hydrogen Evolution Reaction

“…[ 22–24 ] The peak at 133.5 eV in XPS of P 2p is ascribed to PO species owing to superficial oxidation when the sample is exposed to the air. [ 27,33 ] The peaks at 129.05 and 130.05 eV originate from P 2p 3/2 and 2p 1/2 in Ni 2 P–Ni 12 P 5 , respectively (Figure 2b). [ 23 ] The lower binding energy of P 2p 3/2 than P (0) (130.0 eV) suggests that electrons transfer from Ni to P in Ni 2 P–Ni 12 P 5 .…”

Metal‐Rich Chalcogenides for Electrocatalytic Hydrogen Evolution: Activity of Electrodes and Bulk Materials

“…Furthermore, bifunctional NiSe/Ni 3 Se 2 catalysts can be obtained via an optimized hydrothermal method. Notably, the pronounced synergistic NiSe/Ni 3 Se 2 interactions were held responsible for the observed reactivity …”