Photoelectrochemical Production of Hydrogen Peroxide with TiO₂ and 1,5-Di(thien-2-yl)-9,10-anthraquinone via a Selective Two-Electron Oxygen Reduction Reaction in the Two-Compartment Cell

Abstract

The industrial process of hydrogen peroxide (H 2 O 2 ) synthesis proceeds through the hydrogenation of anthraquinone followed by successive oxidation in an organic solvent. This process is a multistep synthesis that is far away from green synthesis. An alternative photoelectrochemical (PEC) H 2 O 2 production method requires only sunlight and water. Herein, we established the direct production of H 2 O 2 by using a two-compartment PEC cell composed of TiO 2 nanorods hydrothermally grown on fluorine-doped tin oxide as a photoanode for water oxidation and 1,5-di(thien-2-yl)-9,10-anthraquinone (AQTh) anchored carbon cloth as a cathode for the selective two-electron (2e – ) reduction of oxygen. This photoanode and cathode are positioned in an anodic compartment and a cathodic compartment of a two-compartment cell, respectively. The Nafion membrane (N-117) separates these two compartments. This PEC cell continuously produces H 2 O 2 at −0.1 V RHE applied voltage, which reaches 60 μM after 3 h. The density functional theory study is carried out to better understand the H 2 O 2 production mechanism and the role of thiophene substituents on anthraquinone.