In‐Situ Sulfuration of Ni(OH)₂ to Heterostructured Ni₃S₂/Ni(OH)₂@Ni Catalyst for Efficient Water Splitting

The exploring and developing non-precious transition metal-based catalysts for practical water electrolysis with the low cost, high efficiency and easy macroscopic preparation was still a challenge. Herein, Ni₃S₂/Ni(OH)₂ heterojunction with different sulfuration time was proposed and hydrothermally synthesized using a simple two-step approach, which served as a bifunctional electrocatalyst for water splitting in alkaline solution at industrial temperature. Among these catalysts, Ni₃S₂/Ni(OH)₂-5h displayed the smallest overpotentials (237 mV@100 mA cm^-2 and 360 mV@100 mA cm^-2) for OER and HER at room temperature, along with low Tafel slopes of 62.0 mV dec^-1 and 80.8 mV dec^-1 respectively. Furthermore, working at high temperature Ni₃S₂/Ni(OH)₂-5h exhibited even lower overpotential of 82 mV@100 mA cm^-2 at 70 °C for OER and 325 mV@100 mA cm^-2 at 60 °C for HER. The excellent performance was ascribed to the heterojunction accelerating the charge transfer, hierarchical interconnected structure promoting the mass transfer and the synergistic effect between the components of Ni₃S₂ and Ni(OH)₂. This work could provide a promising route for promoting the electrocatalytic performance of Ni-based catalyst with a simple sulfuration method for industrial water splitting, which could expand to other non-noble metal-based materials for enhancing the electrocatalytic activities.