Capacitive deionization mechanism and multiple properties of low-temperature etched porous carbon fabric with abundant surface defects

A modified carbon fabric (BNPCF) co-doped with B, N and P, which is abundant in nanopores and surface defects, was prepared at low temperatures using a gentle surface modification method. The BNPCF was used directly as the electrodes for a capacitive deionization (CDI) device, which combines conductivity and ion storage, eliminating the need for a collector like a titanium plate. Among the symmetrical supercapacitors (SSCs) constructed with porous CF electrodes doped with different heteroatoms, the BNPCF showed the most favorable electrochemical performance. It is noteworthy that at a current density of 1 mA cm⁻² in a NaCl electrolyte, the area capacitance reached 1468 mF cm⁻². Furthermore, at a current density of 20 mA cm⁻², the capacitance retention of the device reached 93 % after 20,000 cycles. The enhanced performance of the porous CF was further corroborated by theoretical calculations. The BNPCF-based CDI device possessed a high volumetric adsorption capacity (VAC) of 8.44 mg cm⁻³ and a rapid volumetric adsorption rate (VAR) of 0.56 mg cm⁻³ s⁻¹. Moreover, the BNPCF-based CDI demonstrated high adsorption capacity for heavy metals, with VAC values of 4.16 and 6.98 mg cm⁻³ for Cd²⁺ and Cr³⁺ ions, respectively. This study demonstrates that it is feasible to create BNPCF electrodes, which have high-performance, low-cost and self-supporting characteristics for industrial capacitive desalination equipment.