(486c) Pathways Towards Defect-Tolerate, Electrochemically Stable Solar-Hydrogen Membranes

Defect tolerance in electrochemical corrosion protection is an important concept in chemical engineering devices.  In particular, this concept has been applied to artificial photosynthetic devices that mimics nature’s photosynthesis and use semiconductors to take sunlight and splits water into H₂ and O₂.  Previously, more than half a century of photoelectrochemical (PEC) water splitting research mainly stayed at model systems of semiconductor – non-aqueous electrolyte interfaces, because of oxidative instability of essentially all technologically important small band gap semiconductors. 

In this work, a general corrosion protection strategy for stabilizing semiconductor–electrolyte interfaces for water oxidation and hydrogen production in pH 14 base will be presented.  This has been achieved by introducing complex metal-oxide-semiconductor interfaces from opto-electronics research to photoelectrochemistry.  This not only brings back an entire class of semiconductors that were previously rejected, but also extends PEC theory by introducing new electrochemical models and band diagrams of stabilized semiconductor-electrolyte interfaces.  Furthermore, nanowire-shape semiconductors with conformal protective coatings showed unprecedented > 2200 hours of stability for continuous water oxidation.  This discrete nanowire geometry not only enables manufacture of flexible, nanowire-embedded solar-hydrogen membranes, but also confine defects within the affected region by virtue of self-passivating mechanism under the discrete nanowire geometry.  Finally, I will give an outlook of the materials challenges and opportunities towards scalably manufacturable artificial photosynthetic devices that directly store solar energy into chemical fuels.