Electrochemically derived Bi/BiOCl heterojunction on carbon for capacitive deionization

Bismuth (Bi) has demonstrated great promise as Cl - capture anode for capacitive deionization (CDI), owing to large desalination capacity and environmental benefits. However, Bi anode suffers from severe volume expansion of ∼158% during Cl - capture, leading to electrode degradation and rapid capacity decay. Herein, a two-dimensional Bi/BiOCl heterojunction anchored into carbon microrods (Bi-BiOCl/C) is constructed via tailored electrochemical construction process, which is achieved by ordinal charging-discharging under appropriate voltage. In the two-dimensional (2D) heterojunction, ultrafine Bi nanoparticles tightly bind with in-situ formed BiOCl nanosheet, forming abundant two-phase heterointerfaces. Density functional theory (DFT) calculations demonstrate that significant charge redistribution occurs at Bi/BiOCl interface, greatly promoting Cl - adsorption. Moreover, the robust Bi-O-C bonds not only accelerate electrons transport between heterojunction and carbon, but also strengthen structural integrity of the Bi-BiOCl/C. As expected, the Bi-BiOCl/C anode delivers an impressive Cl⁻ removal capacity of 172.8 mg g −1 at 1.2 V and maintains robust cyclic stability, retaining 86.2% of its initial capacity after 100 cycles. This work paves an efficient path for the design and construction of high-performance CDI electrode.