Multiple Sites Organic Small-Molecule Electrode Material for High-Capacity Seawater Desalination

Redox-active organic materials, especially small molecules, are expected as alternatives to inorganic materials in electrochemical energy storage due to their multisite and high-capacity merits. Inspired by this, herein, we propose an organic small molecular material 1,4,5,8-naphthalenediimide (NDI) with multiple ion insertion sites as an efficient electrode material for seawater desalination. By providing a conductive and confined environment through a double-layer gel encapsulation strategy, we have solved the problem of dissolution and detachment of small molecular materials. Benefitting from multiple sites provided by carbonyl oxygen and the (−1–12) crystal plane, the fabricated composite electrode exhibits remarkable removal capacity for Na+ (145 mg g–1) in 0.5 M NaCl solution. Furthermore, in natural seawater, the composite electrode demonstrates high stability and achieves impressive removal capacities for Na+ (107 mg g–1), Mg2+ (48 mg g–1), Ca2+ (12 mg g–1), and K+ (9.2 mg g–1), respectively. This work has realized the application of multisite small-molecule materials in seawater desalination by solving the problems of dissolution and detachment of organic small molecules, paving the way for developing novel efficient organic materials in electrochemical seawater desalination.