An electrodeposited MoS2-MoO3_ x/Ni3S2 heterostructure electrocatalyst for efficient alkaline hydrogen evolution

To produce H2 more efficiently from water splitting, low-cost, highly active, and robust electrocatalysts based on the earth-abundant elements that could operate in alkaline solutions to lower the energy barrier of the hydrogen evolution reaction (HER) are desired. Herein, we firstly present the fabrication of an amorphous MoS2-MoO3_x/ Ni3S2 heterostructure on the nickel foam (NF) substrate via a facile and low-cost electrochemical synthesis approach consisting of a spontaneous chemical reaction followed by one-step electrodeposition in a single solution. The chemical composition and the content of the bridging S22_ sites (i.e., a highly active site for the HER) in the fabricated MoS2-MoO3_ x/Ni3S2@NF could be conveniently modulated by controlling the temperature and applied potential during the electrodeposition. The optimized MoS2-MoO3_ x/Ni3S2@NF shows an excellent electrocatalytic activity with a HER overpotential of 76 mV at 10 mA cm_ 2 and stabilizes for over 17 h under the HER conditions in a 1 M KOH electrolyte at room temperature, which are the best among the reported MoS2based hybrid electrocatalysts for the alkaline HER. Experimental characterizations and theoretical calculations show that the excellent electrocatalytic performance of the fabricated MoS2-MoO3_x/Ni3S2 heterostructure could be attributed to the synergistic effect of the proper hydrogen binding free energies of MoS2 with abundant bridging S22_ sites, the strong H2O adsorption of MoO3_x, and the strong adsorption of OH_ to the Ni3S2. This study presents a delicately designed MoS2-based hybrid catalyst for efficient alkaline HER, which could shed light on the design and fabrication of inexpensive electrocatalysts for energy conversion.