Metal-organic framework derived carbon nanoarchitectures for highly efficient flow-electrode CDI desalination

Flow-electrode capacitive deionization (FCDI) has shown a robust desalination performance, in which the electrode materials play a crucial role. However, commercial activated carbon (AC) commonly with relatively poor conductivity, which can be a limit to the desalination process. To address this issue, we successfully prepared ZIF-8 derived nanocarbon materials (Zx, X = 0, 1, 2, 3, the number representing the activator ratio) via a pyrolysis activation procedure as electrode materials for FCDI desalination. The results manifested that Z3 achieved desalination rates of 0.0403 and 0.094 mg min^-1 cm^-2 in the isolated closed cycle (ICC) and the short-circuited closed cycle (SCC) mode, respectively, at 1.2 V with only 5 wt% carbon loading. The desalination rate of Z3 in the SCC mode was improved with flow rates and influent salt concentrations increase, reaching 0.278 mg min^-1 cm^-2 under a continuous operation. In the ICC mode, it was found that the adsorption capacity of the Zx sample was positively correlated with its specific surface area. The superior performance of Z3 could be attributed to the high conductivity, large specific surface area and well-developed pores. Overall, this work provided new insights and references for electrode material's application to FCDI desalination.