Enhanced Electrical Conductivity and Seebeck Coefficient in PEDOT:PSS via a Two-Step Ionic liquid and NaBH4 Treatment for Organic Thermoelectrics

A two-step approach of improving the thermoelectric properties of Poly(3,4-ethylenedioxythiophene)poly(4-styrenesulfonate) (PEDOT:PSS) via the addition of the ionic liquid, 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM:TFSI) and subsequent reduction with NaBH4 is presented. The addition of 2.5 v/v% of EMIM:TFSI to PEDOT:PSS increases the electrical conductivity from 3 S·cm-1 to 1439 S·cm-1 at 40 °C. An additional post treatment using the reducing agent, NaBH4, increases the Seebeck coefficient of the film from 11 µV·K-1 to 30 µV·K-1 at 40 °C. The combined treatment gives an overall improvement in power factor increase from 0.04 µW·m-1·K-2 to 33 µW·m-1·K-2 below 140 °C. Raman and XPS measurements show that the increase in PEDOT:PSS conductivity is due to PSS separation from PEDOT and a conformational change of the PEDOT chains from the benzoid to quinoid molecular orientation. The improved Seebeck coefficient is due to a reduction of charge carriers which is evidenced from the UV-VIS depicting the emergence of polarons.

Interaction of the ionic liquid [BMP][TFSA] with rutile TiO2(110) and coadsorbed lithium

The interaction of lithium, [BMP][TFSA] and their mixture with rutile TiO₂(110), the thermal stability of the adlayers and the resulting reaction products are investigated under UHV conditions by STM and XPS.

Spectroscopic study of ionic liquid adsorption from solution onto gold

HMIM NTf₂ adsorbs on gold from ethanol to form a patchy bilayer. ‘Bound’ anion (filled anion) and ‘bound’ cation (filled blue) sit underneath a layer of cation (empty blue) and anion (empty orange). The IL regions are separated by oxidised gold (darker colour).

Spectroscopic characterization of the interaction of lithium with thin films of the ionic liquid 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide

In this experimental investigation lithium and [OMIm]Tf₂N were evaporated in thin films on a copper substrate and reaction products were analyzed by XPS and UPS.

Functionalization of Oxide Surfaces through Reaction with 1,3-Dialkylimidazolium Ionic Liquids

Practical applications of ionic liquids (ILs) often involve IL/oxide interfaces, but little is known regarding their interfacial chemistry. The unusual physicochemical properties of ILs, including their exceptionally low vapor pressure, provide access to such interfaces using a surface science approach in ultrahigh vacuum (UHV). We have applied synchrotron radiation photoelectron spectroscopy (SR-PES) to the study of a thin film of the ionic liquid [C6C1Im][Tf2N] prepared in situ in UHV on ordered stoichiometric CeO2(111) and partially reduced CeO2-x. On the partially reduced surface, we mostly observe decomposition of the anion. On the stoichiometric CeO2(111) surface, however, a layer of surface-anchored organic products with high thermal stability is formed upon reaction of the cation. The suggested acid-base reaction pathway may provide well-defined functionalized IL/solid interfaces on basic oxides.

Influence of the ionic liquid/gas surface on ionic liquid chemistry

Applications such as gas storage, gas separation, NP synthesis and supported ionic liquid phase catalysis depend upon the interaction of different species with the ionic liquid/gas surface. Consequently, these applications cannot proceed to the full extent of their potential without a profound understanding of the surface structure and properties. As a whole, this perspective contains more questions than answers, which demonstrates the current state of the field. Throughout this perspective, crucial questions are posed and a roadmap is proposed to answer these questions. A critical analysis is made of the field of ionic liquid/gas surface structure and properties, and a number of design rules are mined. The effects of ionic additives on the ionic liquid/gas surface structure are presented. A possible driving force for surface formation is discussed that has, to the best of my knowledge, not been postulated in the literature to date. This driving force suggests that for systems composed solely of ions, the rules for surface formation of dilute electrolytes do not apply. The interaction of neutral additives with the ionic liquid/gas surface is discussed. Particular attention is focussed upon H(2)O and CO(2), vital additives for many applications of ionic liquids. Correlations between ionic liquid/gas surface structure and properties, ionic liquid surfaces plus additives, and ionic liquid applications are given.

Corrosion of Ni in 1-butyl-1-methyl-pyrrolidinium bis (trifluoromethylsulfonyl) amide room-temperature ionic liquid: an in situ X-ray imaging and spectromicroscopy study

This paper reports a pioneering application of soft X-ray scanning transmission microscopy (STXM), combined with micro-spot X-ray absorption spectroscopy (XAS) and X-ray fluorescence spectroscopy (XRF), for the investigation of the corrosion of metal electrodes in contact with room-temperature ionic liquids (RTIL). Using an open electrochemical cell in vacuo we explore some fundamental aspects of the aggressiveness of the 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)amide ([BMP][TFSA]) RTIL towards Ni under in situ electrochemical polarisation. The possibility of imaging electrochemically-induced morphological features in conjunction with micro-XAS and XRF spectroscopies has provided unprecedented details regarding the space distribution and chemical state of corrosion products.