Fe-N/C anode with pseudocapacitive behavior derived from Fe-modified ZIF-8/C composites for phosphorus capture

Capacitive deionization (CDI) is a promising phosphorus (P) electrosorption technology with no secondary pollution, cost-effectiveness, energy efficiency, and easy regeneration. In this study, Fe-N/C composites have been successfully synthesized for phosphorus capture. The optimal Fe-N/C-1000 electrode presented higher electrosorption performance and low energy consumption (3.823 kWh/kg (1.447 ×10−2 kWh/m3)) for 5 mg P/L solution than Fe-N/C-900 and Fe-N/C-800 at 1.2 V, which was owed to its superior conductive network, high specific surface area, and abundant Fe-Nx sites. The diffusion-controlled process (pseudocapacitive) contributed more significantly to the electrosorption of Fe-N/C-1000 than the capacitance-controlled process. The effects of key operational factors on phosphorus uptake in the CDI process, and the corresponding kinetics and Ragone plot were also discussed in detail. The phosphorus capture mechanism was fully explicated by discussing the characterization data and experimental results. This study may provide new insight for further applications of low-cost Fe-N/C in CDI processes.