[Mo ₇ O ₂₄ ] ⁶– Polyoxometalate Coupled with Ni-MOF as a Nanohybrid Electrocatalyst for the Oxygen Evolution Reaction and Supercapacitors

Herein, we developed the polyoxometalate ([Mo7O24]6–, POM) combined with a nickel metal-organic framework (MOF) as the POM@Ni-MOF electrocatalyst for increasing oxygen evolution reaction (OER) kinetics and serving as an active electrode for supercapacitors. The POM@Ni-MOF with a layer-like morphology is beneficial for promoting charge and mass transport during the OER. The developed electrocatalyst (Ni-MOF:Mo2) demonstrates efficient activity toward the OER with a low overpotential of 237 mV at 50 mA cm–2 in 1 M KOH. The incorporation of POMs into the MOF stimulates catalytic activity by introducing a high density of electroactive sites. The interaction between [Mo7O24]6– and the imidazole N sites of Ni-MOF is attributed to hydrogen-bonding interactions mediated by confined water molecules at the interface leading to an increase in electrocatalytic activity. A remarkable electrochemical durability (5000 CV cycles and CP) with negligible performance deterioration was attained for the Ni-MOF:Mo2 electrocatalyst. The Ni-MOF:Mo2//Pt/C system demonstrated an overall water splitting requirement of 1.80 V at 30 mA cm–2. Moreover, the Ni-MOF:Mo2 electrode demonstrates an outstanding supercapacitor performance of 2351 F g–1 at 1 A g–1 in 3 M KOH. This hybrid system is promising for high-performance water electrolysis electrocatalysts and supercapacitor electrodes due to the efficacy of combining POM species with MOF structures.