Zeolitic Imidazolate Framework-Derived CoS@NiFe-LDH Core-Shell Heterostructure as Efficient Bifunctional Electrocatalyst for Water Splitting.

The development of stable and efficient bifunctional electrocatalysts is of utmost importance for overall water splitting. This study introduces CoS@NiFe-LDH core-shell heterostructure prepared via an electrodeposition of ultrathin NiFe-LDH nanosheet on zeolitic imidazolium framework-derived CoS nanosheet arrays. The bifunctional CoS@NiFe-LDH/NF exhibits impressive catalytic performance and long-term stability for both the OER and HER with low overpotentials of 100 mA cm at 235 mV and 10 mA cm at 95 mV in 1 M KOH, respectively. The assembled cell with CoS@NiFe-LDH/NF as both cathode and anode shows voltages of 1.595 and 1.666 V at current densities of 10 and 20 mA cm, respectively, as well as ultralong stability over 500 h. DFT calculations expose a robust electron interaction at the heterogeneous interface of the CoS@NiFe-LDH/NF core-shell structure. This interaction promotes electron transfer from NiFe-LDH to CoS and reduces the energy barriers for OER intermediates, thereby enhancing electrocatalytic activity. This research contributes novel insights toward the promising materials for electrochemical water splitting through the construction of heterojunction interfaces.