Controlled synthesis of ZnO modified N-doped porous carbon nanofiber membrane for highly efficient removal of heavy metal ions by capacitive deionization

Abstract

Capacitive deionization (CDI), known as an emerging, environment-friendly, energy-efficient and cost-effective technology, has gained tremendous attention and shown great application potential in brackish water desalination. However, the limited electrical double layer (EDL) capacitance and desalination capacity of conventional carbon-based electrodes seriously affect its practical application. Here, we prepared a flexible, self-supporting, zinc oxide-modified N-doped porous carbon nanofiber membrane (ZnO@N-PCNM) as capacitive deionized electrode materials. The prepared carbon membrane possesses a large specific surface area (488.6 m2 g−1) due to the interconnected and hierarchical multi-layer pores, which can provide more adsorption sites and good electronic/ion conductivity. In addition, benefiting from the high N-doping (10.9%) and the loading of Zn, the prepared ZnO@N-PCNM electrode shows a specific capacitance of 253.62 F g-1 in 3 M KOH electrolyte at a scanning rate of 5 mV s−1. As electrode materials for CDI, the ZnO@N-PCNM delivers an outstanding electrosorption capacities of 32.87 mg g−1, 23.81 mg g−1 and 20.85 mg g−1 at a low pressure of 1.8 V for heavy metal ions Pb2+, Cu2+, and Cd2+, respectively. These results mean that the prepared ZnO@N-PCNM membrane has great potential for Hybrid capacitive deionization practical applications.