Heteromorphic NiCo 2 S 4 /Ni 3 S 2 /Ni Foam as a Self-Standing Electrode for Hydrogen Evolution Reaction in Alkaline Solution.

Considerable works have been devoted on developing high-efficiency nonplatinum electrocatalysts for hydrogen evolution reaction (HER). Herein, 3D heteromorphic NiCo2 S4 /Ni3 S2 nanosheets network has been constructed on Ni foam (denoted as NiCo2 S4 /Ni3 S2 /NF) serving as a self-standing electrocatalyst through directly thermal sulfurization of a single-source NiCo-layered double hydroxide precursor. The resultant NiCo2 S4 /Ni3 S2 /NF electrode exhibits outstanding electrocatalytic HER performance with an extremely low onset overpotential of 15 mV and long-term durability in alkaline solution. Such enhanced HER performance can be credited to (1) the massive exposed active sites provided by mixed transition metal chalcogenides (NiCo2 S4 and Ni3 S2 ), (2) the strong interfacial interaction at NiCo2 S4 /Ni3 S2 heterojunction interfaces with the strengthened H binding, and (3) the porous highly conductive Ni foam substrate with accelerated electron transfer. This work opens up a new direction to fabricate effective and non-noble-metal electrodes for water splitting and hydrogen generation.