Activated Carbon Derived from <i>Phoenix dactylifera</i> (Palm Tree) and Decorated with MnO <sub>2</sub> Nanoparticles for Enhanced Hybrid Capacitive Deionization Electrodes
G. Bharath, Emad Alhseinat, Ismail Darawsheh, Issam Ismail, Kyriaki Polychronopoulou, Maguy Abi Jaoudé, Abdul Fahim Arangadi, Fawzi Banat
Abstract
Abstract In this study, the electro‐sorption capacity and selectivity of activated carbon (AC) electrodes, produced from the leaf base of Phoenix dactylifera (palm tree) waste, are modified by enabling the reversible intercalation/conversion of sodium ions through the presence of nanoscale α‐MnO 2 particles acting as redox mediators. The α‐MnO 2 nanoparticles (NPs) are hydrothermally grown on the AC powder to obtain a functional composite material (α‐MnO 2 /f‐AC). The morphological, textural, and physicochemical surface properties of the pristine and modified AC materials are thoroughly examined and correlated with the electrochemical performance of the resulting electrodes that are implemented in an asymmetric capacitive deionization (CDI) cell configuration (i. e. capacitive vs Faradaic electrodes). The pristine biowaste‐derived AC presents a high specific surface area of 1224 m 2 g −1 , and high electrical capacitance of 259 F g −1 at 10 mV s −1 . The α‐MnO 2 surface modification approach of the pristine material retains its large accessible surface area, and additionally enables a 50% increase in its specific capacitance value. The incorporation of the α‐MnO 2 /f‐AC material in the anode and the pristine source in the cathode produces superior electrosorption capacity, as high as 17.8mgg −1 in batch‐mode CDI tests with 600mg L −1 NaCl feed. The enhanced electrical performance and pseudocapacitive behavior of the CDI cell can be explained by the α‐MnO 2 nanoparticles playing a critical role in enabling a synergistic redox‐based charge‐discharge pathway under conditions compatible with the voltage operation requirements of the CDI process.