Liquid–liquid interfacial processes at hydrophobic silica carbon composite electrodes: ion transfer at water–nitrobenzene, water–o-nitrophenyloctylether, and at water–o-nitrophenylphenylether interfaces

Ion transfer processes across liquid–liquid phase boundaries of the type aqueous solution–polar organic solvent supported on a hydrophobic silica carbon composite are studied by cyclic voltammetry and differential pulse voltammetry. The organic phase consists of a redox probe (ferrocene, t-butylferrocene, or decamethylferrocene) dissolved in a polar hydrophobic solvent (nitrobenzene, o-nitrophenyloctylether, or o-nitrophenylphenylether). The organic phase was immobilised in a ceramic carbon material composed of a hydrophobic silicate prepared via a sol–gel process from a methyltrimethoxysilane based sol and carbon particles. When immersed into aqueous electrolyte, ion transfer processes can be monitored as a function of potential. The contributions of solvent, electrolyte, and redox probe to the transition from anion transfer to cation transfer are discussed. Effects due to the presence of a high surface area microporous solid matrix are considered.