Synergistic mechanism of Ni(OH)2/NiMoS heterostructure electrocatalyst with crystalline/amorphous interfaces for efficient hydrogen evolution over all pH ranges

Designing and fabricating efficient electrocatalysts is a practical step toward the commercial application of the efficient hydrogen evolution reaction (HER) over all pH ranges. Herein, novel Ti@Ni(OH)2-NiMoS heterostructure with interface between crystalline Ni(OH)2 and amorphous NiMoS was rationally designed and fabricated on Ti mesh (denoted as Ti@Ni(OH)2-NiMoS). Acid etching and calcination experiments helped in accurate elucidation of the synergistic mechanism as well as the vital role on crystalline Ni(OH)2 and amorphous NiMoS. In acidic solutions, the HER performance of Ti@Ni(OH)2-NiMoS was mainly attributed to the amorphous NiMoS. In neutral, alkaline, and natural seawater solutions, the HER performance was mainly determined by the synergistic interface behaviors between the Ni(OH)2 and NiMoS. The crystalline Ni(OH)2 accelerated water dissociation kinetics, while the amorphous NiMoS provided abundant active sites and allowed for fast electron transfer rates. To deliver current densities of 10 mA·cm-2 in acidic, neutral, alkaline, and natural seawater solutions, the Ti@Ni(OH)2-NiMoS required overpotentials of 138, 198, 180 and 371 mV, respectively. This paper provides general guidelines for designing efficient electrocatalyst with crystalline/amorphous interfaces for efficient hydrogen evolution over all-pH ranges.