Titanium Carbon Oxide Flakes with Tunable Interlayer Spacing for Efficient Capacitive Deionization

Abstract The environmental toxicity caused by heavy metal ions is always taken seriously. Capacitive deionization (CDI), as an emerging and effective treatment method, is widely studied. Among them, the rational design and development of efficient electrodes based on high theoretical capacitance, high conductivity, and high stability have great prospects for CDI applications. In this study, a series of 2D titanium carbide oxide flakes (2D TCOs) are synthesized using a cation‐giving modulation strategy, and the interlayer spacing of materials is successfully controlled by confining cations (tetraalkylammonium hydroxides, TAAH) with different radii between layers. Interestingly, these TCOs exhibit widely varying electrochemical properties due to their different interlayer spacings. Among them, titanium carbide oxide flakes‐tetrapropylammonium hydroxide (TCOs‐TPAH) with the maximum interlayer spacing exhibits the best performance in sodium ion embedding and de‐embedding, with a capacity of 53.11 mg g⁻¹. In addition, the capacitive removal efficiency of heavy metal ions (Fe³⁺, Cr³⁺, Cu²⁺, Cd²⁺, Co²⁺, Ni²⁺, and Pb²⁺) can reach over 97% within 2 h. This work presents a simple and creative strategy for the bottom‐up synthesis of oversized 2D nanomaterials, thus supporting the further development of high‐performance 2D materials in the fields of environmental and energy applications.