Oxygen vacancy-rich Ti (sub)oxide electrodes boost desalination performance on hybrid capacitive deionization (HCDI) platforms

The potential of capacitive deionization (CDI) for sustainable desalination depends critically on breakthroughs in electrode materials. Defect-rich titanium (sub) oxides (anatase TiO₂(A), Ti₂O₃, Ti₃O₅, Ti₄O₇) offer compelling advantages, including tunable capacity, low environmental impact, and robustness. This study provides a systematic comparison of their structural features, electrochemical responses, and desalination efficacy. Electrochemical characterization results show anatase TiO₂(A) leads in specific capacitance (252.5 F g −1 at 0.3 A g −1 ), while Ti₃O₅’s highest oxygen vacancy minimizes charge transfer resistance and maximizes ion migration rates. In desalination trials, TiO₂ delivers a maximum salt adsorption capacity of 37.1 mg g −1 (500 mg L −1 NaCl, 1.2 V). All electrodes exhibit outstanding cycling stability (capacity retentions >83.5 %), affirming their practical potential. Correlation analysis discloses the oxygen vacancy-driven charge transfer mechanism inside these electrodes and establishes a structure-performance relationship. Overall, this work establishes fundamental structure-property relationships that underpin future electrode innovation via the oxygen vacancy-engineering strategy, which represents a promising pathway for advancing CDI performance boundaries.