3D Coral-Like Ni3S2 on Ni Foam as a Bifunctional Electrocatalyst for Overall Water Splitting.

High-performance noble metal-free electrocatalysts are extremely desired for overall water splitting, but there are huge challenges. Herein, we report a novel one-step electrochemical anodic oxidation and cathodic deposition strategy to in situ fabricate three-dimensional coral-like Ni3S2 on Ni foam (NF) for electrocatalytic overall water splitting. In a typical two-electrode cell, NF acts as both cathodic and anodic electrodes with thiourea aqueous solution as the electrolyte. The nickel ions from the anodic oxidation of NF are directly used as nickel sources to form 3D coral-like Ni3S2/NF by the cathodic deposition method simultaneously. The optimal 3D Ni3S2/NF-4 electrode shows high electrocatalytic activity for hydrogen evolution reaction and oxygen evolution reaction with low overpotentials of 89 and 242 mV, respectively, to afford 10 mA cm-2. When the as-obtained Ni3S2/NF-4 is used as a bifunctional electrocatalyst in an electrolyzer, a low applied voltage of 1.577 V is needed to reach 10 mA cm-2, with extremely long durability. This work focuses on the rational design of unique structures as efficient non-noble metal-based electrocatalysts, which hold great potential for practical applications in electrocatalytic water splitting.