A novel layered activated carbon with rapid ion transport through chemical activation of chestnut inner shell for capacitive deionization

Abstract

Capacitive deionization is a very promising method for future water desalination. However, desalination capacity and rate limit its wide application. In this study, a layered activated carbon with rapid ion transport was synthesized by carbonizing and activating chestnut inner shell with KOH. The effects of carbonization temperature and the ratio of KOH have been studied through structural characterization and electrochemical tests. All biochar showed lamellar structure and high specific surface area (>1000 m2 g−1), and the one obtained at 500 °C (CS500) exhibited the highest specific surface area (1943.2 m2 g−1) and more oxygen-containing functional groups. Correspondingly, CS500 brought excellent capacitance (127.2 F g−1, 5 mV s−1) and small internal resistance. Moreover, CS500 achieved a significant average salt adsorption rate of 5.7 mg g−1 min−1, with a high salt adsorption capacity of 17.7 mg g−1 and 21.0 mg g−1 in NaCl (0.5 g L−1) and CaCl2 (0.95 g L−1), respectively. Additionally, CS500 showed a preferential adsorption for Ca2+ in a mixed solution with Na+, suggesting its potential for hard water softening. Lastly, CS500 maintained high cycle stability (87.0%, 1.2 V) within 50 adsorption/desorption cycles. Thus, this work supports CS500 as a promising candidate for rapid desalination and large-scale application.