Mn-Doped Crystalline Ni3S2/Amorphous MoS2 Core–Shell Nanorods as Bifunctional Electrocatalysts for Highly-Efficient Overall Water Splitting

Molybdenum disulfide (MoS2), a typical earth-abundant material, is an excellent candidate for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), which fundamentally rely on the regulation of the morphology and electronic structure of MoS2. Herein, Mn-doped amorphous MoS2 coated on Mn-doped crystalline Ni3S2 nanorods (Mn–Ni3S2@MoS2), rationally designed core–shell nanorods, have been fabricated via a facile one-step hydrothermal method as highly efficient bifunctional activities for HER and OER in alkaline solution. The target electrodes deliver a high current density of 100 mA cm–2 at a low overpotential of 187 and 310 mV for HER and OER, respectively, outperforming most MoS2-based catalysts. Moreover, a water-splitting cell based on the Mn–Ni3S2@MoS2 electrode requires a voltage of 1.45 V to reach a current density of 10 mA cm–2, which is superior to the state-of-the-art one of those based on noble metal Pt/C–NF∥RuO2–NF and non-noble metal catalysts. The overall enhanced bifunctional catalytic performance is mainly attributed to the abundant catalytically active sites provided by the Mn-doped amorphous MoS2 and the fast pathway for electron/proton transfer facilitated by the Mn-doped crystalline Ni3S2 nanorods. The incorporated Mn dopants and assembled Ni3S2/MoS2 heterostructure effectively regulate the electronic structure with redistributed charge within the core–shell Mn–Ni3S2@MoS2 electrode.