Photoelectrochemical measurements of a heterosupramolecular system under visible light irradiation

Abstract

A photochemical system utilising a modular approach characterised through interpretation of photoelectrochemical measurements is discussed. A photoanode was prepared by the chemisorption of a photosensitiser, cis-bis-(2,2′-bipyridine)-(4,4′-bis-(methyl)phosphonato-2,2′-bipyridine)ruthenium(II) dichloride (RuL₂L′²⁺), to a mixed nanoporous nanocrystalline RuO₂:TiO₂ thin film, calcined on a fluorine doped SnO₂ conducting glass substrate. Similarly, an electron relay molecule, 1-ethyl-1′-(2-phosphonoethyl)-4,4′-bipyridinium dichloride (EVP), was covalently bound to a platinum electroplated nanoporous nanocrystalline TiO₂ thin film, and the electrodes connected in a photoelectrocatalytic cell (PCC). Irradiation with λ > 420 nm gave a measurable photocurrent. Interpretation of the photocurrents obtained from this assembly provides a means for understanding photochemical reactions under low light intensities. Optimised conditions of the electrolyte solution were determined to be pH = 5 and illumination yielded η = 0.0036% with an apparent quantum yield (AQY) = 1.6%.