Use of steam to prepare super active carbon with large pore volume for efficient capacitive deionization

Abstract

Active carbons simultaneously possessing large surface area (>2000 m2/g) and high pore volume (>2.0 cm3/g) are pretty promising electrode materials for capacitive desalination. However, it is challenging to find a simple, cheap, and scalable method for preparing such materials. In this research, H3PO4-loaded coconut shell was fast heated in steam flow to yield active carbon for capacitive desalination. The as-yielded active carbon simultaneously displayed large specific surface area (2869 m2/g), high pore volume (2.26 cm3/g), and big micropore volume (0.83 cm3/g). Because of these characteristics, the carbon showed an electrosorption capacity of 64.1 mg/g in a membrane capacitive deionization (MCDI) configuration at 1.2 V in 500 mg/L NaCl solution. The capacity ranked among the highest values ever reported for C-based materials. The capacity retention exceeded 86 % after 20 adsorption/desorption cycles. Besides, the carbon showed high charge efficiency (92.4 %) and desalination rate. This research was beneficial for scalable synthesis of carbon materials for CDI.