Constructing ion-transport blockchain by polypyrrole to link CoTi-ZIF-9 derived carbon materials for high-performance seawater desalination

The instability and poor electronic conductivity of carbon materials derived from bimetallic zeolite imidazolate frameworks (ZIFs) pose significant challenges for utilizing these carbon materials as direct electrodes for achieving rapid electron transfer and high-performance capacitive deionization (CDI). However, modifying ZIFs through conductive polymers is a wise tool to enhance the target characteristics of ZIFs. Herein, a strategy is proposed to use polypyrrole (PPy) to interlink the carbon units derived from CoTi-ZIF-9 to construct a blockchain network system with high capacity and fast electrochemical kinetics for high performance CDI. In this system, PPy serves as a branched link connecting each carbon unit, so that the ions in the electrolyte can achieve low barrier and fast transmission in the three-dimensional network structure between the unit structures. As expected, with the improved charge transfer efficiency between electrode materials and electrolyte, the CDI cell exhibits excellent desalination capacity (77.3 mg g-1). In addition, density functional theory calculations also indicate that the introduction of PPy results in a higher electron density near the fermi surface of carbon material, which is conducive to electron transport and reaction kinetics. This work may provide important concepts for the design of CDI electrodes with high-conductivity and high-performance.