Conductive Agent Insights for Flow-Electrodes Capacitive Deionization

Abstract

Flow-electrode capacitive deionization (FCDI) enables continuous desalination, yet its performance is fundamentally governed by charge storage and transport within the flow electrodes. Despite extensive use of conductive additives, the role of their intrinsic physicochemical properties in determining desalination behavior remains poorly understood. Here, we systematically reveal how the particle size and surface potential of conductive additives regulate inter–particle interactions and slurry viscosity, thereby controlling flow dynamics and desalination efficiency. Combined experimental measurements and numerical simulations show that, compared with Ketjen Black, carbon nanotubes possess larger particle sizes and share the same surface charge polarity as activated carbon, leading to substantially reduced slurry viscosity and improved flow stability. Coupled with their higher intrinsic capacitance, these features enable flow electrodes to deliver enhanced desalination performance. This work provides guidelines for the rational selection and optimization of conductive additives, advancing the design of high-performance FCDI systems for desalination.