Nickel-Glycerolate/MOF-Based Electrode Materials for Energy Storage and Water-Splitting Applications

Herein, binary coordination compounds based on Ni-Gly/ZIF-67 and Ni-Gly/CoFe-ZIF-67 were employed as electrode materials for energy storage and water-splitting applications, respectively. The structure and morphology of the binary electrodes were characterized by XRD, XPS, and SEM. Electrochemical studies (cyclic voltammetry and electrochemical impedance spectroscopy) revealed that the binary materials exhibited distinct electrochemical behavior for energy storage and water splitting. In fact, whereas Ni-Gly/ZIF-67 was used as an electrode material for energy storage, Ni-Gly/CoFe-ZIF-67 was used as an electrocatalyst for water splitting. The Ni-Gly/ZIF-67 electrode material achieved a high specific capacity of 106.9 mA h g^-1 at 1.0 A g^-1 and retained 71.6% of its capacity after 5000 cycles, combining pseudocapacitive/battery-type behavior. Furthermore, a symmetric supercapacitor device was assembled, achieving maximum energy and power densities of 0.765 W h kg^-1 and 6076 W kg^-1, respectively. The Ni-Gly/CoFe-ZIF-67 electrode material exhibited excellent oxygen evolution reaction (OER) activity, with an overpotential of 430 mV at 10 mA cm^-2, a Tafel slope of 108 mV dec^-1, and stable operation for 10 h. These results demonstrate a synergism between MOF- and Ni-Gly-derived frameworks, providing valuable insights for the rational design of sustainable multifunctional electrodes for integrated energy storage and conversion systems.