Mo-doped Ni3S4 nanosheets grown on carbonized wood as highly efficient and durable electrocatalysts for water splitting

Rational design and fabrication of nonprecious metal-based electrocatalysts with high activity and excellent stability for overall water splitting (OWS) is still a grand challenge. Here we report a novel electrocatalyst constructed by incorporating molybdenum into the Ni3S4 lattices grown on carbonized wood (denoted as Mo-Ni3S4/CW). Experimental results and density functional theory (DFT)-based calculations demonstrate that lattice expansion of Ni3S4 caused by Mo doping optimizes adsorption energy of hydrogen/oxygen species and regulates local charge density of active sites, which promote the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Also, a nickel (oxy)hydroxide (Ni-OOH) layer generated via surface reconstruction of Ni3S4 nanosheets improves the intrinsic activity for OER. Moreover, the 3D low-tortuosity porous CW substrate increases the exposure of active specific surface, accelerates the rates of electron transfer, electrolyte diffusion, and gas products escaping. Accordingly, an optimized electrocatalyst (Mo-Ni3S4/CW-0.4) exhibits ultralow overpotentials of 17 and 240 mV for HER and OER at 10 mA cm−2, respectively. Besides, an electrolyzer composed of Mo-Ni3S4/CW-0.4 electrodes as both the anode and cathode shows a low cell voltage of 1.46 V at 10 mA cm−2 while maintaining superior durability over 50 h for OWS. Further, it requires only 0.19 V to achieve 10 mA cm−2 for hydrazine oxidation-assisted water electrolysis, indicating highly attractive potential for economical hydrogen production coupling with pollutants treatment.