Self-supported Ni3S2@MoS2 core/shell nanorod arrays via decoration with CoS as a highly active and efficient electrocatalyst for hydrogen evolution and oxygen evolution reactions
A hierarchically porous MoS 2 on Ni 3 S 2 nanorod array on Ni foam (MoS 2 /Ni 3 S 2 /NF) was firstly fabricated through a simple microwave-assisted hydrothermal method , and then followed by electrochemical deposition approach in which MoS 2 /Ni 3 S 2 /Ni foam is decorated with CoS (CoS MoS 2 /Ni 3 S 2 /NF). In contrast to conventional hydrothermal approach, microwave irradiation accelerates the synthesis of MoS 2 /Ni 3 S 2 /Ni foam from time of >20 h–2 h. The characterization of CoS MoS 2 /Ni 3 S 2 /NF by scanning electron microscope (SEM) and high resolution transmission electron microscope (HRTEM) indicate that a whole scale of 1D the Ni 3 S 2 nanorods were hierarchically integrated with MoS 2 and CoS nanosheets . The as-synthesized CoS MoS 2 /Ni 3 S 2 /NF hybrid not only endows the ease transport of electrons along Ni 3 S 2 nanorods to Ni foam, but also accommodates maximal exposure of active edge sites to the reactants through hierarchically porous CoS doped MoS 2 nanosheets , accomplishing the promoted kinetics and activity for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). By electrochemical measurements such as linear sweep voltammetry (LSV) and electrochemical impedance spectroscope (EIS), we find that the CoS MoS 2 /Ni 3 S 2 /NF hybrid shows markedly enhanced electrochemical performance for both HER and OER. Specifically, the optimal CoS MoS 2 /Ni 3 S 2 /NF 8C possesses the low overpotentials (η 10 ) of 85 and 225 mV at current density (|j|) of 10 mA cm −2 in 1.0 M KOH and the small 62.3 and 46.1 mV dec −1 Tafel slope for HER and OER, respectively, outperforming those of most of the current noble metal-free electrocatalysts . These results highlight the fact that CoS MoS 2 /Ni 3 S 2 /NF is a high-performance, noble-metal-free electro-catalyst, and provide a potential avenue toward achieving an enhanced electrocatalytic activity towards both in HER and OER. Yet the duration of the as prepared catalyst in OER still need to be improved.
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