4 years ago

Substrate Effects in Graphene-Based Electric Double-Layer Capacitors: The Pivotal Interplays between Ions and Solvents

Substrate Effects in Graphene-Based Electric Double-Layer Capacitors: The Pivotal Interplays between Ions and Solvents
Kefa Cen, Zheng Bo, Jing Kong, Huachao Yang, Jianhua Yan, Xia Chen, Jinyuan Yang
Graphene has been considered as a promising active material for electric double-layer capacitors (EDLCs), primarily owing to its extraordinary monolayer properties, whereas the interfacial behaviors are conspicuously impacted by underlying substrates. In this work, substrate effects on the interfacial wettability, EDL structure, and capacitive behavior of graphene-based EDLCs are delineated with numerical simulation. Unlike previous studies, a partial wetting transparency of topmost graphene is recognized for hydrophilic supports. In particular, a virtually identical capacitance is demonstrated for graphene with various supports, albeit the substantially different EDL structures stemmed from substrate effects. The achieved invariant capacitance is prominently attributed to the counterbalancing correlations between ions and proximal solvents, going beyond traditional views of modulating capacitance preferentially through ion structural evolutions. Specifically, the suppressed permittivity of apparently ordered water dipoles (i. e. detrimental solvent effects) attenuates the beneficial ionic influences (i. e. reinforced population and closer approach) on shielding the external electric fields. The as-obtained findings demonstrate the paramount importance of the substrate in mediating interfacial behaviors within electrified EDLC systems and highlight that exploiting the pivotal interplay between ions and solvents could be a novel avenue to further manipulate electrochemical performances. Evaluation of substrate effects: The influences of substrate on interfacial structure and capacitive behavior of graphene-based supercapacitors are demonstrated with numerical simulation. A partial wetting transparency of graphene is observed. Unusually, an analogous capacitance is recognized, albeit with strikingly different electrolyte structures. The pivotal interplays between ions and solvents in mediating the capacitance are demonstrated, going beyond traditional views.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/celc.201700733

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