Binder free hierarchical mixed capacitive deionization electrode based on polyoxometalate and polypyrrole for brackish water desalination
Capacitive deionization technology is an efficient method for brackish water desalination, in which the electrode plays a vital role and determines its performance directly. Compared with traditional double-layer capacitance deionization electrode, mixed capacitive deionization electrode possesses obvious advantages, because it integrates pseudocapacitance and double-layer capacitance together. A brand-new mixed capacitive deionization electrode is fabricated by co-deposition P2Mo18O626- and polypyrrole on 3D exfoliated graphite matrix with electrochemical technique. In this electrode, composite particles composed by P2Mo18O626- and polypyrrole distribute evenly on 3D exfoliated graphite matrix. Under 1 A•g-1 current, the specific capacitance of this electrode achieves 156.2 mAh•g-1. Its rate capability is also promising with more than 76.5 % capacitance left when current increases to 20 A•g-1. Under 1.2 V voltage, its desalination capacity and rate reach 17.8 mg•g-1 and 1.12 mg•g-1•min-1 in 600 mg•L-1 NaCl. The satisfactory desalination performance is credited to the unique electrochemical properties of P2Mo18O623- and polypyrrole, as well as the binder free character of this electrode. After 100 cycle experiment, its desalination ability does not decay, which confirms its excellent stability. This work confirms the prospect of polyoxometalate based electrode in brackish water desalination.