Titanium and Zinc Oxide Nanoparticles Are Proton-Coupled Electron Transfer Agents

• Published in: Science (American Association for the Advancement of Science) 2012-06, Vol.336 (6086), p.1298-1301
• Main Authors: Schrauben, Joel N., Hayoun, Rebecca, Valdez, Carolyn N., Braten, Miles, Fridley, Lila, Mayer, James M.
• Format: Article
• Language: English
• Subjects: Catalysis; Chemistry; Colloidal state and disperse state; Electron transfer; Electron transfer reactions; Electrons; Exact sciences and technology; Free Radicals - chemistry; General and physical chemistry; Hydrogen-Ion Concentration; Irradiation; Kinetics; Materials; Metal Nanoparticles - chemistry; Nanoparticles; Nitrogen Oxides - chemistry; Optimization; Oxidation-Reduction; Oxides; Phenols - chemistry; Photochemistry; Physical and chemical studies. Granulometry. Electrokinetic phenomena; Physical chemistry of induced reactions (with radiations, particles and ultrasonics); Protons; Radicals; Scientific Concepts; Solvents; Surface chemistry; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Thermodynamics; Titanium; Titanium - chemistry; Titration; Zinc; Zinc Oxide - chemistry; Zinc oxides
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.1220234

Oxidation/reduction reactions at metal oxide surfaces are important to emerging solar energy conversion processes, photocatalysis, and geochemical transformations. Here we show that the usual description of these reactions as electron transfers is incomplete. Reduced TiO₂ and ZnO nanoparticles in solution can transfer an electron and a proton to phenoxyl and nitroxyl radicals, indicating that e⁻ and H⁺ are coupled in this interfacial reaction. These proton-coupled electron transfer (PCET) reactions are rapid and quantitative. The identification of metal oxide surfaces as PCET reagents has implications for the understanding and development of chemical energy technologies, which will rely on e⁻/H⁺ coupling.