Bismuth-titanium alloy nanoparticle@porous carbon composite as efficient and stable Cl-storage electrode for electrochemical desalination

The bismuth (Bi)-based materials have been considered as a promising Cl-storage electrode for electrochemical desalination (EDI), with high theoretical capacity and excellent Cl- selectivity. Unfortunately, the desalination application of Bi-based materials is greatly restricted by poor cycling stability due to the volume expansion and pulverization in the chlorination/dechlorination process. Hence, bismuth-titanium alloy nanoparticles encapsulated in porous carbon matrix composite (Bi-Ti@C) were fabricated by facile pyrolysis of the Bi-Ti bimetallic organic framework (Bi-Ti-MOF). The introduction of Ti and carbon nanocages can effectively buffer the volume expansion and improve the BiTi-C interface binding force during the desalination/salinization process. With these advantages, the alloyed Bi-Ti@C-600 composite exhibited outstanding electrochemical properties, with high specific capacitance of 430.72F g(-1) and low charge transfer resistance. Furthermore, the excellent desalination performance was achieved as an anode coupling with an activated carbon cathode, which delivered an impressive Cl- removal capacity of 106.5 mg g(-1) and superior cycling stability of 80% retention rate after 100 desalination/salination cycles. Importantly, ex-situ XRD patterns revealed the desalination/salinization mechanism of Bi-Ti@C-600 composites involving the reversible transformation between Bi and BiOCl. Our findings shed light on the rational design for high-performance alloyed Bi-based Cl-storage electrode and offer new insights into the applications of EDI.