Nanowire for Solar-to-Fuel Conversion

Direct solar energy conversion to storable fuels such as hydrogen offers a promising route toward less reliance on fossil fuels. For example, photoelectrolysis of water to generate H2 on a semiconductor/electrolyte interface has the attractive advantages of clean processing and energy savings over steam reforming of natural gas. One of the most critical issues in solar water splitting is the development of a photoanode with high efficiency and long-term durability in an aqueous environment. TiO2 has been extensively studied as a photoanode due to its high resistance to photocorrosion. However, its conversion efficiency of solar energy to hydrogen is still low due to its large bandgap. Semiconductor heterojunctions can absorb a different region of the solar spectrum. The advantage of composite structures is that each semiconductor needs to satisfy one energetic requirement: matching the conduction band minimum (CBM) or VBM with either the H2 reduction or O2 oxidation potential. Single semiconductor materials typically cannot satisfy the requirements of suitable bandgap energies for efficient solar absorption and meantime with band-edges aligned with both the H2 and O2 redox potential of water. We are currently exploring semiconductor nanowire heterojunctions for the direct solar-to-fuel conversion.

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