Elaborate Designed Three-Dimensional Hierarchical Conductive MOF/LDH/CF Nanoarchitectures for Superior Capacitive Deionization

Abstract

Rational exploration of cost-effective, durable, and high-performance electrode materials is imperative for advancing the progress of capacitive deionization (CDI). The integration of multicomponent layered double hydroxides (LDHs) with conjugated conductive metal–organic frameworks (c-MOFs) to fabricate bifunctional heterostructure electrode materials is considered a complex but promising strategy. Herein, the fabrication of elaborately designed three-dimensional hierarchical conductive MOF/LDH/CF nanoarchitectures (M–CAT/LDH/CF) as CDI anodes via a controllable grafted-growth strategy is reported. In this assembly, carbon fiber (CF) provides exceptional electrical conductivity facilitating rapid ion transfer and acts as a sturdy foundation for even distribution of NiCoCu-LDH nanosheets. Moreover, the well-ordered NiCoCu-LDH further acts as interior templates to create an interface by embedding c-MOFs and aligning two crystal lattice systems, facilitating the graft growth of c-MOFs/LDH heterostructures along the LDH nanosheet arrays on CF, leading to accelerated ion diffusion kinetics. Density functional theory (DFT) confirms the unique structure of M–CAT/LDH/CF promotes interfacial charge transfer from NiCoCu-LDH to M–CAT. This enhancement accelerates ion transfer, decreases ion migration energy, and leads to better ion diffusion kinetics and a smoother Cl⁻ shuttle. Accordingly, the asymmetrical M–CAT/LDH/CF cell exhibited superior specific capacitance (315 F g⁻¹), excellent salt adsorption capacity (147.8 mg g⁻¹), rapid rate (21.1 mg g⁻¹ min⁻¹), and impressive cyclic stability (91.4 % retention rate). This work offers valuable insights for designing heterostructure electrode materials based on three-dimensional interconnected networks, contributing to further advancements in CDI technology.