PEDOT:PSS for capacitive deionization

Capacitive deionization (CDI) is an energy efficient brackish water desalination technique allows low voltage operation (~ 1.2V) under room temperature and pressure. Carbon material is the most studied material for CDI electrodes. However, the maximum salt adsorption capacity (MSAC) of carbon CDI have reached a limit (~20 mg/g). We have developed an in-situ CDI performance measurement system and tested the desalination performance of CDI cell with activated carbon electrodes and PEDOT:PSS electrodes. Conductivity change of solution inside our CDI cell was monitored during the desalination process. The dependence of salt adsorption on potential difference between CDI electrodes and feed water concentration have been investigated. We compared the desalination behavior of our all-polymer CDI cell with activated carbon and demonstrated that the two materials work in different physical principles. Most notably, the PEDOT:PSS cell has an MSAC that increases with salinity, suggesting its use in applications beyond the desalination of brackish water. An MSAC of over 55 mg/g have been obtained for our PEDOT:PSS CDI system in desalination of 10 g/L salt solution.