Fe 2 W 18 Fe 4 @MOF-Ni-100 nanocomposite: Insights into synthesis and application as a promising material towards the electrocatalytic water oxidation

In this research, a new nanocomposite was synthesized via the sol–gel method by encapsulation of tetranuclear sandwich-type hetropolyanion (Na 9 K[(FeW 9 O 34 ) 2 Fe 4 (H 2 O) 2 ].32H 2 O, abbreviated as Fe 2 W 18 Fe 4, on the surface of MOF-Ni-100 for the first time. The as-prepared nanocomposite (Fe 2 W 18 Fe 4 @MOF-Ni-100) was examined using different microscopy and spectroscopy techniques, including FT-IR, UV–vis, XRD, SEM, EDX, and BET techniques. The assembled Fe 2 W 18 Fe 4 @MOF-Ni-100 nanocomposite served as a potential heterogeneous catalyst in the water oxidation process for the purpose of oxygen evolution reaction (OER) at neutral pH conditions (N 2 -saturated 0.1 M Na 2 SO 4 ). The electrochemical characteristics of the Fe 2 W 18 Fe 4 @MOF-Ni-100 nanocomposite was assessed through cyclic voltammetry (CV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS) methods. The desired nanocatalyst displayed a low onset potential of 1.1 V vs. NHE and low overpotential of 269 mV at a current density (j) of 10 mAĊcm −2 with a Tafel slope of 73 mV.dec −1 (pH = 7). Furthermore, the Fe 2 W 18 Fe 4 @MOF-Ni-100 nanocomposite exhibited remarkable stability and retained its catalytic activity even after 200 catalytic cycles.