Ion-ion correlations across and between electrified graphene layers

Abstract

When an ionic liquid adsorbs onto a porous electrode, its ionic arrangement is deeply modified due to a screening of the Coulombic interactions by the metallic surface and by the confinement imposed upon it by the electrode's morphology. In particular, ions of the same charge can approach at close contact, leading to the formation of a superionic state. The impact of an electrified surface placed between two liquid phases is much less understood. Here we simulate a full supercapacitor made of the 1-butyl-3-methylimidazolium hexafluorophosphate and nanoporous graphene electrodes, with varying distances between the graphene sheets. The electrodes are held at constant potential by allowing the carbon charges to fluctuate. Under strong confinement conditions, we show that ions of the same charge tend to adsorb in front of each other across the graphene plane. These correlations are allowed by the formation of a highly localized image charge on the carbon atoms between the ions. They are suppressed in larger pores, when the liquid adopts a bilayer structure between the graphene sheets. These effects are qualitatively similar to the recent templating effects which have been reported during the growth of nanocrystals on a graphene substrate.

Theoretical Aspects of Ionic Liquids for Soft‐Matter Sciences

“…Charge‐ordering of ionic liquids has drawn much attention in both theoretical and experimental studies . Of particular importance is the fact that the Coulombic interaction, dielectric response, and hydrogen bonding often equally organize the charge ordering .…”

Performance of Microporous Carbon Electrodes for Supercapacitors: Comparing Graphene with Disordered Materials

“…As shown in our recent study focusing on the structure of the liquid, a monolayer of ions is formed for separations ranging between 7 and 9 Å, but in the 10 Å this monolayer is split in two, leading to two subpeaks with smaller intensities. 24 Therefore the cations that still remain inside the pores are very close to the carbon surface and are therefore at the origin of the observed large negative charges in the 7 Å nanoporous graphene. In the CDC electrode, the structure is very different: There are several pore sizes within the material (ranging from 7 Å to 10 Å); this 6 allows strong reorganizations of the liquid structure.…”

Kalium Permanganat: Termodinamika Mengenai Transport Ionik dalam Air

“…Konduktivitas listrik (162)(163)(164)(165)(166) adalah ukuran kemampuan suatu larutan (167)(168)(169)(170)(171)(172)(173) untuk menghantarkan arus listrik .Arus listrik di dalam larutan dihantarkan oleh ion yang terkandung didalamnya.Ion memliki karakteristik tersendiri dalam menghantarkan arus listrik.Maka dari itu nilai konduktivitas listrik hanya menunjukan konsentrasi ion total dalam larutan.Banyaknnya ion di dalam larutan juga dipengaruhi oleh padatan terlarut didalamnya.Semakin besar jumlah padatan terlarut didalam larutan maka kemungkinan jumlah ion dalam larutan juga akan semakin besar, sehingga nilai konduktivitas listrik juga akan semakin besar.Dapat dilihat bahwa terdapat hubungan antara jumlah zat padat terlarut yang dinyatakan dengan TDS dengan nilai konduktivitas listrik.Eletrolit kuat (174)(175)(176)(177)(178)(179) adalah zat yang terionisasi sempurna dalam larutan dan meliputi padatan ion dan asam kuat.Sebagai hasil pengionan sempurna , konsentrasi ion dalam larutan sebanding dengan konsentrasi elektrolit yang ditambahkan .Berdasarkan data mengenai konduktivitas larutan KMnO 4 yang telah dilakukan yaitu :…”