Soft carbon electrodes in capacitive energy extraction: exploring geometry and operational parameters in capacitive mixing systems†

Abstract

The global challenge of water scarcity, intensified by a growing population, climate change, and increased demand for fresh water, requires immediate investigation of innovative and sustainable technologies. Capacitive deionization (CDI) and capacitive mixing (CapMix) have emerged as promising solutions, leveraging the electric double layer (EDL) formed at the interface of charged surfaces and electrolytic solutions. The initial technique represents a promising approach to water desalination and ionic separation, as CapMix is a reciprocal technique for energy obtention from exchanging solutions with varying salinity. This study focuses on the use of carbon electrodes with polyelectrolyte (PE) coatings for capacitive energy extraction based on Donnan potential (CDP) in CapMix systems. This investigation considers the impact of applied current, volumetric charge densities of the PEs, and geometric parameters, such as electrode separation distance, on the efficiency and scalability of these systems. The findings provide valuable insights for enhancing energy extraction performance and overcoming challenges associated with electrode use in these applications.