Self-supported Ni₃Se₂@NiFe layered double hydroxide bifunctional electrocatalyst for overall water splitting

Low-cost, highly active and earth-abundant bifunctional electrocatalyst is very important for the large-scale hydrogen production by water splitting. In the present work, we report a novel two-step method to fabricate three-dimensional (3D) porous catalyst for water splitting. The Ni₃Se₂ nanowires are in-situ formed on Ni foam (NF) by simple hydrothermal method, subsequently NiFe layered double hydroxid (NiFe-LDH) nanosheets vertically grow on the nanowires to form core-shell structure. The as-formed Ni₃Se₂@NiFe-LDH/NF catalyst shows 3D porous structure, which can provide large specific surface area and effective substance transfers. The tight bonding between Ni₃Se₂ nanowires and NiFe-LDH nanosheets ensures good electron transfer. The Ni₃Se₂@NiFe-LDH/NF catalyst exhibits outstanding electrocatalytic property for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in an alkaline medium. The overpotentianls for HER and OER at the current density of 10 mA cm^-2 in 1 M KOH are 68 mV and 222 mV, respectively. For overall water splitting, a small cell voltage of 1.55 V can achieve a current density of 10 mA cm^-2 in 1 M KOH. This work provides a guidance for the rational design and development of heterostructure electrocatalysts for overall water splitting.