Fe-Doped Ni/Co-Based Selenide Hierarchical Nanosheet Arrays as Self-Supporting Bifunctional Electrocatalysts for Overall Water Splitting

It is necessary to optimize the electrocatalytic activity of an electrocatalyst by means of morphology and composition regulation. Herein, Fe-doped bimetallic selenide hierarchical nanosheet arrays grown on nickel foam (Fe-NiCoSe/NiCoSe/NF) are obtained for overall water splitting. The Fe-NiCoSe/NiCoSe/NF is fabricated by selenizing the NiCoFe Prussian blue analogue (NiCoFe-PBA) growing on a NiCo-layered double hydroxide (NiCo-LDH). Benefiting from the hierarchical nanosheet arrays, the synergistic effect of the bimetallic selenides, as well as the electronic structure rearrangement caused by Fe-doping, the Fe-NiCoSe/NiCoSe/NF catalyst exhibits low overpotentials of 120 mV for hydrogen evolution reaction (HER) and 199 mV for oxygen evolution reaction (OER) at 10 mA·cm–2 in 1.0 M KOH. In addition, when used as a bifunctional electrocatalyst for overall water splitting, the Fe-NiCoSe/NiCoSe/NF requires a cell voltage of 1.93 V (1.82 V) to reach 100 mA·cm–2 (50 mA·cm–2). Additionally, Fe-NiCoSe/NiCoSe/NF exhibits prolonged durability lasting for 150 h at 10 mA·cm–2. This work provides a reasonable idea for designing a hierarchical nanostructured bifunctional electrocatalyst toward overall water splitting by regulating the structure and composition.