Crafting an Exceptionally Redox-Active Organic Molecule Boasting Superior Electron Mobility for High-Performance Electrochemical Desalination

Abstract

Access to freshwater is crucial for a sustainable environment and human ecosystems. Hybrid capacitive deionization (HCDI) based on attractive pseudocapacitive reactions is considered a promising environmentally friendly and energy-saving electrochemical desalination technology. However, the application of HCDI technology is still limited, mainly due to the unsatisfactory ion adsorption ability of the pseudocapacitive electrode. Herein, we unveil an innovative redox-active organic molecule (PATD) that showcases outstanding pseudocapacitive properties for electrochemical desalination. Notably, the integration of redox-active C═O and C═N groups in the PATD molecule promotes stable and efficient pseudocapacitive reactions. Additionally, the rigid molecular structure, combined with a minimal HOMO–LUMO energy gap, ensures exceptional redox characteristics and superior electron transfer capability of the PATD molecule, which are substantiated by experimental evidence and theoretical studies. As an electrode, the PATD molecule exhibits significant pseudocapacitive characteristics along with excellent long-term stability, retaining 89.0% of its capacitance after 5000 cycles in a NaCl aqueous solution. In practical applications, the developed HCDI device incorporating the PATD electrode demonstrates a remarkably high salt removal capacity of 56.9 mg g^–1, a swift average removal rate of 1.9 mg g^–1 min^–1, and consistent regeneration performance while attaining reliable energy recovery, which highlights its promising prospects for sustainable desalination technologies.