Synthesis of Ni‐Doped Copper Cobalt Sulfide Nanoparticles and its Enhanced Properties as an Electrocatalyst for Hydrogen Evolution Reaction.

Developing high‐efficiency electrocatalysts for hydrogen evolution reaction (HER) is vitally important in electrochemical water splitting technology. Herein, ultra‐small Ni‐doped CuCo2S4 nanoparticles (NCCS NPs) are easily achieved in a single step by a facile hydrothermal method. The investigations, using powder X‐ray diffraction, X‐ray photoelectron spectroscopy, scanning electron microscopy, and TEM, reveal that the as‐prepared NCCS products are composed of a large number of uniform nanoparticles with sizes ranging from 20 to 50 nm. Triethanolamine is of vital importance for the formation of the NCCS NPs during the sulfidation process. As a promising electrocatalyst for HER, the NCCS NPs not only display a lower overpotential at 10 mA cm−2 current density than that of bare CuCo2S4 nanoparticles (CCS NPs), but also show better long‐term durability than CCS NPs during the galvanostatic electrolysis. Furthermore, Ni doping for NCCS NPs are proved to play a particular important role in the HER process. This finding provides a strategy in compositional tuning of mixed polymetallic sulfides catalysts for electrochemical hydrogen evolution. Ultra‐small Ni‐doped CuCo2S4 nanoparticles (NCCS NPs) are easily achieved in one step by hydrothermal method. The formation mechanism of NCCS NPs during the sulfidation process is proposed. Ni doping for NCCS NPs is proved to play a critical role in the catalysis of Hydrogen Evolution Reaction (HER). This finding provides a strategy in compositional tuning of polymetallic sulfides for HER. [ABSTRACT FROM AUTHOR]