Formation of interior hollow nanocubes derived from cobalt-based metal-organic frameworks via one-step etching for efficient battery desalination

Battery desalination (BD) offers a sustainable solution for simultaneous energy storage and desalination, addressing the global need for clean water access. However, current BD technologies require improvements in salt removal capacity, charge efficiency and energy consumption to become practical. In this study, we present a BD system utilizing interior hollow nanocubes derived from a cobalt-based zeolitic imidazolate framework (Co-TA HC) as the cathode and silver nanoparticle on reduced graphene oxide (Ag@rGO) as the anode. The regular and hollow nanocubes, with enhanced specific surface area and abundant redox active sites, are prepared via a simple one-step mild tannic acid (TA) etching process, holding great promise for scalable manufacturing. The unique structure of the Co-TA HC significantly shortens the diffusion length of the Na⁺ and enhances the sodium intercalation kinetics, as indicated by the galvanostatic intermittent titration technique. The optimal pairing of the Co-TA HC and Ag@rGO enables the full discharge with voltage window of 0–1.4 V in the BD system, achieving high volumetric salt adsorption capacity (SAC) of 102.3 mg cm⁻³ and gravimetric SAC of 143.2 mg g⁻¹ with a current density of 100 mA g⁻¹. This suggests that the practical application of BD systems is a tangible possibility and paves the way for scaling-up emerging desalination technologies.