Stress-Induced Bandgap-Shifted Titania Photocatalyst for Hydrogen Generation

Phase II will continue developing the efficient production of hydrogen from water using sunlight and nanostructured titania thin-film semiconductor electrodes achieved in Phase I, delivering a solar hydrogen generator. Titania?s (TiO2) absorption cutoff is moved from UV (414 nm) to visible (529 nm) by shifting the energy bandgap to 2.0 eV , through stress induced by the nanostructured template. The disorder/strain distribution forms amorphous/strained titania with a high density of states localized within the energy band gap. Absorption of 29% of the solar spectrum is achieved, more than 5X improvement over single-crystal TiO2. The nanostructures enhance total absorption through multiple total internal reflections, eliminating the need to track the sun. A prototype three-electrode electrochemical cell evolves hydrogen at 2 mL/(s?W?m2) ? a solar-efficiency of 8% after light source correction; electrochemistry data shows 20% efficiency is attainable. Efficient conversion of water to hydrogen fuel with sunlight is ideal for closed environments like the International Space Station, with continuous recycling of hydrogen from contaminated water back to clean water when combined with a fuel-cell electrical generator. With possible water on the moon, Mars, and other bodies in the solar system, this technology will greatly reduce the mass of space ships for future missions.