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

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 SiW12 O40 4- and polyaniline on a 3D exfoliated graphite carrier. In this electrode, SiW12 O40 4- /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 SiW12 O40 4- and polyaniline. This work has developed polyoxometalate as a new material for capacitive-deionization electrodes.