Green activation of rice straw porous carbon via potassium citrate for capacitive Deionization
摘要
Capacitive deionization (CDI) is an energy-efficient and promising technology for desalination of brackish water, and the selection and preparation of electrode materials are the core of capacitive deionization. However, the exploration of green and low-cost porous carbon electrodes with optimal desalination performance remains a significant challenge. In this study, biomass-based porous carbon electrode materials were synthesized by one-step pyrolysis through the activation strategy of potassium citrate using rice straw as a carbon source and potassium citrate as an activator. The results demonstrated that the incorporation of potassium citrate into the rice straw-derived porous carbon (RK-x) material resulted in an augmentation of its specific surface area, an enhancement of its pore structure, and an increase in defect density. The pore sizes of RK-x predominantly distributed around 1.74 nm (micropores) and 3.93 nm (mesopores), supplemented by macropores, collectively forming its hierarchical pore structure. These structural modifications were found to have a substantial impact on the electrochemical properties of RK-x, leading to a significant enhancement in its capacitance and adsorption performance. RK-3 exhibited optimal specific surface area (722.18 m2·g− 1), maximum pore volume (0.5879 cm3·g− 1), superior wettability (contact angle of 48.50°), and good specific capacitance (156.25 F·g− 1, 0.5 A·g− 1). The salt adsorption capacity of RK-3 was 16.26 mg·g− 1 in a 500 mg·L− 1 NaCl solution at 1.2 V, and 93.78% (15.25 mg·g− 1) desalting capacity was maintained after 10 adsorption/desorption cycles. This study provides a new inspiration for the design of green and economical carbon-based electrodes for CDI desalination.