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

•Crystalline Ni(OH)2/Amorphous NiMoS electrocatalyst were designed and synthesized by two-step hydrothermal process.•The as-obtained material shows excellent hydrogen evolution over all pH ranges.•The synergistic mechanism and the role of crystalline Ni(OH)2 and amorphous NiMoS was elucidated.