MoS2/Ni3S2 nanorod arrays well-aligned on Ni foam: a 3D hierarchical efficient bifunctional catalytic electrode for overall water splitting

Abstract

Fabricating earth-abundant bifunctional water splitting electrocatalysts with high efficiencies to substitute Pt and IrO₂ is in great demand for the development of clean energy conversion technologies. Via a simple one-step hydrothermal procedure, MoS₂/Ni₃S₂ nanorod arrays well-aligned on Ni foam (MoS₂/Ni₃S₂/NF) as a novel three dimensional (3D) hierarchical bifunctional catalytic electrode for overall water splitting has been successfully fabricated in this work. Ni foam (NF) as both 3D substrate and Ni source realized the uniform, dense and nearly vertical in situ self-growth of MoS₂/Ni₃S₂ nanorods on it. Each nanorod had a coated structure with large surface contact regions. Benefiting from the elaborately designed architecture, MoS₂/Ni₃S₂/NF exhibited excellent catalytic activity and good stability for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in an alkaline electrolyte. To reach the catalytic current density of 10, 100, 200, and 300 mA cm⁻², it only required 187, 274, 300, and 320 mV overpotential for HER and 217, 275, 313, and 335 mV overpotential for OER respectively. Moreover, by employing MoS₂/Ni₃S₂/NF as both the cathode and anode, the water splitting electrolyzer achieved excellent durability. Besides, it only needed very low cell voltages of 1.467, 1.593, 1.640 and 1.661 V to reach the current density of 10, 100, 200 and 300 mA cm⁻², respectively, better than the performance of a benchmark combination. Therefore, MoS₂/Ni₃S₂/NF is a promising non-noble-based bifunctional electrocatalyst for overall water splitting.