Modulation of electronic structure of Ni3S2 via Fe and Mo co-doping to enhance the bifunctional electrocatalytic activities for HER and OER

Heazlewoodite nickel sulfide (Ni 3 S 2 ) is advocated as a promising nonnoble catalyst for electrochemical water splitting because of its unique structure configuration and high conductivity. However, the low active sites and strong sulfur–hydrogen bonds (S–H ads ) formed on Ni 3 S 2 surface greatly inhibit the desorption of H ads and reduce the hydrogen and oxygen evolution reaction (HER and OER) activity. Doping is a valid strategy to stimulate the intrinsic catalytic activity of pristine Ni 3 S 2 via modifying the active site. Herein, the Ni foam supported Fe and Mo co-doped Ni 3 S 2 electrocatalysts (Fe-MoS 2 /Ni 3 S 2 @NF) have been constructed using Keplerate polyoxomolybdate {Mo 72 F 30 } as precursor through a facile hydrothermal process. Experimental results certificate that Fe and Mo co-doping can effectively tune the local electronic structure, facilitate the interfacial electron transfer, and improve the intrinsic activity. Consequently, the Fe-MoS 2 /Ni 3 S 2 @NF display more excellent HER and OER activity than MoS 2 /Ni 3 S 2 @NF and bare Ni 3 S 2 @NF by delivering the 10 and 50 mA cm −2 current densities at ultra-low overpotentials of 74/175 and 80/160 mV for HER and OER. Moreover, when coupled in an alkaline electrolyzer, Fe-MoS 2 /Ni 3 S 2 @NF approached the current of 10 mA cm −2 under a cell voltage of 1.60 V and exhibit excellent stability. The strategy to realize tunable catalytic behaviors via foreign metal doping provides a new avenue to optimize the water splitting catalysts.