Jordan Cole

The thermal and moisture stability of halide perovskites is significantly improved by combining imidazolium ionic liquid additives (BMIMBF ₄ and BMIMCl) with a SnO ₂ electron transport layer.

Superbasic ionic liquids (SBILs) are being investigated as potential carbon dioxide (CO₂) gas capture agents, however, the presence of H₂O in the flue stream can inhibit the uptake of CO₂. In this study a thin film of the SBIL trihexyltetradecylphosphonium 1,2,4-triazolide ([P₆₆₆₁₄][124Triz]) was deposited onto rutile TiO₂ (110) using in situ electrospray deposition and studied upon exposure to CO₂ and H₂O using in situ near-ambient pressure x-ray photoelectron spectroscopy (NAP-XPS). The molar uptake ratio of gas in the electrosprayed SBIL (n _gas :n _IL) was calculated to be 0.3:1 for CO₂, 0.7:1 for H₂O, and 0.9:1 for a CO₂/H₂O mixture. NAP-XPS taken at two different depths reveals that the competitive absorption of CO₂ and H₂O in [P₆₆₆₁₄][124Triz] varies with sampling depth. A greater concentration of CO₂ absorbs in the bulk layers, while more H₂O adsorbs/absorbs at the surface. The presence of H₂O in the gas mixture does not inhibit the absorption of CO₂. Measurements taken during exposure and after the removal of gas indicate that CO₂ absorbed in the bulk does so reversibly, whilst CO₂ adsorbed/absorbed at the surface does so irreversibly. This is contrary to the fully reversible CO₂ reaction shown for bulk ionic liquids (ILs) in literature and suggests that irreversible absorption of CO₂ in our highly-structured thin films is largely attributed to reactions at the surface. This has potential implications on IL gas capture and thin film IL catalysis applications.

The adsorption of 4-mercaptobenzoic acid (4-MBA) on anatase (101) and rutile (110) TiO₂ surfaces has been studied using synchrotron radiation photoelectron spectroscopy and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy techniques. Photoelectron spectroscopy results suggest that the 4-MBA molecule bonds to both TiO₂ surfaces through the carboxyl group, following deprotonation in a bidentate geometry. Carbon K-edge NEXAFS spectra show that the phenyl ring of the 4-MBA molecule is oriented at 70° ± 5° from the surface on both the rutile (110) and anatase (101) surfaces, although there are subtle differences in the electronic structure of the molecule following adsorption between the two surfaces.

Ionic liquids (ILs) supported on oxide surfaces are being investigated for numerous applications including catalysis, batteries, capacitors, transistors, lubricants, solar cells, corrosion inhibitors, nanoparticle synthesis and biomedical applications. The study of ILs with oxide surfaces presents challenges both experimentally and computationally. The interaction between ILs and oxide surfaces can be rather complex, with defects in the oxide surface playing a key role in the adsorption behaviour and resulting electronic properties. The choice of the cation/anion pair is also important and can influence molecular ordering and electronic properties at the interface. These controllable interfacial behaviours make ionic liquid/oxide systems desirable for a number of different technological applications as well as being utilised for nanoparticle synthesis. This topical review aims to bring together recent experimental and theoretical work on the interaction of ILs with oxide surfaces, including TiO₂, ZnO, Al₂O₃, SnO₂ and transition metal oxides. It focusses on the behaviour of ILs at model single crystal surfaces, the interaction between ILs and nanoparticulate oxides, and their performance in prototype devices.