The polymeric conformational effect on capacitive deionization performance of graphene oxide/polypyrrole composite electrode

Exploitation of novel faradic electrode materials is an alternative implementation for
solving the problem of poor specific electrosorption capacity that conventional
carbon-based electrodes are encountered in capacitive deionization. Particularly,
composite electrode is just an suitable choice because of its potentially high
ion-storage ability. Herein, a cyclic voltammetric treatment method with different low
limit of potential window were used to manipulate the polymeric conformation and
doping level of graphene oxide/polypyrrole (GO/PPy) composite electrode. Based on
it, the effect of polymeric structure on the electro-sorption performance was
systematically studied. When the low limit of potential window is shifted to a
potential negative enough, the irreversible polymeric conformational shrinks of
GO/PPy electrode are promoted, which not only hinders the insertion process of ionsin the composite matrix, but also decrease the doping level of polymer due to the intensive interchain interaction produced by more entangled polymeric chain. Thus,
the number of intercalated ions should decrease, which is expressed by EIS results
and is proportional to the electro-sorption capacity of GO/PPy composite electrode in
MCDI process. Our work suggest that the less packing density, higher doping level
and more charge delocalization on PPy backbone in composite electrode is beneficial
to enhance its capacitive deionization performance.