Spinel Nickel Ferrite on Metal–Organic Framework-Derived Porous Carbon as a Robust Faradaic Electrode for Enhanced Flow Capacitive Deionization

Abstract

Water desalination by capacitive deionization techniques has often suffered from the relegating performance of carbon-based non-Faradaic electrode materials. To overcome the rate-limiting charge transfer kinetics and weak ion adsorption tendency, a metal–organic framework (MOF)-derived hybrid electrode with an exceptional flow capacitive deionization performance is reported here. Using MIL-88(FeNi) as a sacrificial template, we synthesized a porous graphitic framework decorated with nanosized spinel NiFe₂O₄ (NiFe₂O₄@PC-500) electrodes, maintaining a parent rod-shaped morphology with a large surface area of 1227 m²/g. The synergistic interaction of NiFe₂O₄ nanoparticles with the mesoporous graphitic framework exhibited remarkable desalination performance with a salt adsorption capacity of ∼34 mg/g and ∼89% salt removal at 1.2 V, surpassing those of traditional carbon-based electrodes. Moreover, NiFe₂O₄@PC-500 maintained its desalination capacity and structural integrity over prolonged desalination cycles with a specific capacitance of ∼206 F/g and capacitive retention over 500 cycles. This study presents a universal approach for strategically implementing MOF-derived heterostructures as potent flow electrode materials.