Poly-p-phenylene as a novel pseudocapacitive anode or cathode material for hybrid capacitive deionization
Weiqing Kong, Xu Ge, Mengqi Yang, Qingao Zhang, Jingyi Lu, Haokun Wen, Hanyu Wen, Desheng Kong, Meng Zhang, Xiao Zhu, Yuanyuan Feng
Abstract
Hybrid capacitive deionization (HCDI), which consists of one Faradaic and one carbon electrode, has recently developed as a high-efficiency and environmentally friendly water desalination technique. The advancement of HCDI, however, is hampered by a scarcity of high quality Faradaic materials. Here we demonstrated that conducting poly- p -phenylene (PPP) with a coplanar molecular structure of the extended Π-conjugated skeleton can be used as a reversible electrode material to capture either cations (Na + , K + , Ca 2+ ) or anions (Cl − , F − , NO 3 − , and SO 4 2− ) from various salt solutions. This is benefited from its broad potential window and n−/p-doping characteristics. The desalination performance of PPP was evaluated systematically with the constructed HCDI cells in different electrolytes, which can deliver excellent salt adsorption capacity, charge efficiency, and long-term cycling stability. Further, based on complex capacitance analysis, the kinetic features and mechanism for the ion insertion-adsorption processes were further elucidated, which offers both a new perspective for understanding the salt removal performance of PPP and a practical method for investigating other pseudocapacitive intercalation materials.