Role of Mesopore Structure of Hierarchical Porous Carbons on the Electrosorption Performance of Capacitive Deionization Electrodes

Capacitive deionization (CDI) is a promising alternative approach for water desalination and treatment. Hierarchical porous carbons, HPCs, have been viewed as a promising porous structure material for electrosorption purposes. However, limitations associated with the synthesis and porosity control of HPCs limit their utilization as model systems in correlating the textural characteristics and the CDI performance. Here we report for the first time a systematic investigation using a wide range of tightly control primary mesopore size, mesopore surface area, mesopore volume, and high mesopore fraction synthesized by the ice templation approach and correlate to their CDI performance. Larger mesopores are preferable for faster ion removal as they can provide easier pathways for the ions to diffuse and establish the electric double layer. However, smaller mesopores are more preferable in order to achieve higher salt capacity. While for meso-macro HPCs the salt capacity scales up with the mesopore surface area, HPCs that contain all levels of porosity (i.e. micro-meso-macro) do not show such correlation. Besides the excellent CDI performance reported, the model systems allow us to delineate of the role of several materials design parameters and correlate with their electrosorption behavior.