Elaborately assembled core-shell structured metal sulfides as a bifunctional catalyst for highly efficient electrochemical overall water splitting

Low efficiency, short lifetimes, and limited kinds of catalysts are still three fundamental shortcomings that have plagued electrochemical water splitting. Herein, we rationally synthesized a cost-effective Co₃S₄@MoS₂ hetero-structured catalyst that has proven to be a highly active and stable bifunctional catalyst for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in an alkaline environment. The heterostructure was obtained via a first hydrothermal approach to obtain hollow Co₃S₄ nanoboxes based on the ionic exchange reaction between Fe(CN)₆ ³⁻ of Co-Fe Prussian blue analogue (PBA) and S²⁻ at 120 °C, and the subsequent in situ growth of MoS₂ nanosheets on the surface of Co₃S₄ nanoboxes at an elevated temperature of 200 °C. The synergistic effects between the active and stable HER catalyst of MoS₂ and the efficient OER catalyst of Co₃S₄, as well as the morphological superiority of hollow and core-shell structures, endow Co₃S₄@MoS₂ with remarkable electrocatalytic performance and robust durability toward overall water splitting. As a result, the designed non-noble electrocatalyst of Co₃S₄@MoS₂ exhibits a low overpotential of 280 mV for OER and 136 mV for HER at a current density of 10 mA cm⁻² in an alkaline solution. Meanwhile, a low cell voltage of 1.58 V is achieved by using the heterostructure as both anode and cathode catalysts. This work paves the way to the design and construction of other prominent electrocatalysts for overall water splitting.