A Polyoxometalate-Based Binder-Free Capacitive Deionization Electrode for Highly Efficient Sea Water Desalination

Abstract

Capacitive deionization is a promising technique in sea water desalination. Compared with common electrodes, mixed capacitive-deionization electrodes exhibit better performance in sea water desalination because they integrate pseudocapacitance and electric double-layer capacitance in one system. Herein, a 3D binder-free mixed capacitive-deionization electrode was fabricated by direct electrodeposition of SiW12O404- and polyaniline on a 3D exfoliated graphite carrier. In this electrode, SiW12O404-/polyaniline composite particles with a size of about 100-120 nm are dispersed homogenously on the 3D exfoliated graphite carrier. Its specific capacitance reaches 352 F g(-1) at 1 A g(-1). With increasing current from 1 to 20 A g(-1), the specific capacitance only decays by 32 %. When employed in sea water desalination, the performance of this mixed capacitive-deionization electrode is also excellent. At 1.2 V, the salt adsorption capacity of this mixed electrode reaches 23.1 mg g(-1) with a salt adsorption rate of 1.38 mg g(-1) min(-1) in 500 mg L-1 NaCl. The performance of this electrode is well retained after 30 cycles. The excellent sea water desalination performance originates from the synergistic effect between SiW12O404- and polyaniline. This work has developed polyoxometalate as a new material for capacitive-deionization electrodes.