Photoelectrochemical Characterization of a Robust TiO2/BDD Heterojunction Electrode for Sensing Application in Aqueous Solutions

Abstract

Titanium dioxide (TiO2) and boron-doped diamond (BDD) are two of the most popular functional materials in recent years. In this work, TiO2 nanoparticles were immobilized onto the BDD electrodes by a dip-coating technique. Continuous and uniform mixed-phase (anatase and rutile) and pure-anatase TiO2/BDD electrodes were obtained after calcination processes at 700 and 450 ì respectively. The particle sizes of both types of TiO2 film range from 20 to 30 nm. In comparison with a TiO2/indium tin oxide (ITO) electrode, the TiO2/BDD electrode demonstrates a higher photoelectrocatalytic activity toward the oxidation of organic compounds, such as glucose and potassium hydrogen phthalate. Among all the tested TiO2 electrodes, the mixed-phase TiO2/BDD electrode demonstrated the highest photoelectrocatalytic activity, which can be attributed to the formation of the p-n heterojunction between TiO2 and BDD. The electrode was subsequently used to detect a wide spectrum of organic compounds in aqueous solution using a steady-state current method. An excellent linear relationship between the steady-state photocurrents and equivalent organic concentrations was attained. The steady-state oxidation photocurrents of the mixed-phase TiO2/BDD electrode were insensitive to pH in the range of pH 2-10. Furthermore, the electrodes exhibited excellent robustness under strong acidic conditions that the TiO2/ITO electrodes cannot stand. These characteristics bestow the mixed-phaseTiO2/BDD electrode to be a versatile material for the sensing of organic compounds.