Sandwich-Structured Fe-Ni₂P/MoS_x/NF Bifunctional Electrocatalyst for Overall Water Splitting

Exploring cost-efficient, high-active bifunctional electrochemical catalysts with long-term stability are significant for green economy. Herein, a noble-metal-free sandwich-structured catalyst, prepared with facile hydrothermal method and phosphorization process, in which the amorphous MoS_x serves as an intermediate layer between the Fe-doped Ni₂P and Ni foam substrate (Fe-Ni₂P/MoS_x/NF) is reported. The obtained free-standing catalyst performs an enhanced electrochemical activity compared with Fe-Ni₂P/NF and MoS_x/NF. The Fe-Ni₂P/MoS_x/NF catalyst only requires overpotentials of 246 mV to achieve 10 mA cm⁻² and 277 mV to reach 50 mA cm⁻² for oxygen evolution reaction process with a low Tafel slope of 59.7 mV dec⁻¹ in alkaline solution. Meanwhile, an overpotential of 112 mV is demanded to reach 10 mA cm⁻² for hydrogen evolution reaction. When the Fe-Ni₂P/MoS_x/NF is used as two electrodes for overall water splitting, it requires 1.61 V to attain 10 mA cm⁻² with prominent durability. This approach provides a versatile strategy to construct excellent bifunctional catalysts for effective water electrolysis.