In situ chemical etching of tunable 3D Ni₃S₂ superstructures for bifunctional electrocatalysts for overall water splitting

Three-dimensional (3D) nanomaterials are rendered with large specific surface areas as well as desired physicochemical, electrical and catalytic properties for a large variety of functional applications. In this work, 3D Ni₃S₂ superstructures (needle array and leaf pattern) were created on nickel foams (NFs) through an in situ chemical etching (ICE) method. This anisotropic growth involves chemical dissolution, in situ nucleation and re-deposition processes, which endows the as-fabricated Ni₃S₂ with large surface areas and warrants firm adhesion to the NF as well. Importantly, the Ni₃S₂@NF can directly serve as effective binder-free electrodes for hydrogen evolution reactions (HERs) and oxygen evolution reactions (OERs) from electrocatalytic water splitting.