PHOTOELECTROCHEMICAL WATER-SPLITTING WITH PLASMONIC Al-BASED NANOSTRUCTURES
Youngmin Lee, Chris Bohn, Ting Xu, Heayoung Yoon, Eric Walter, Henri Lezec, Veronika Szalai and A. Alec Talin
Photoelectrochemical (PEC) water-splitting using semiconductor electrodes is currently the subject of intense research as a renewable energy alternative to fossil fuels. However, PEC electrodes fabricated from low cost, earth abundant, and chemically stable materials show low solar-to-hydrogen conversion efficiency because the electrode thickness necessary to absorb a large fraction of the incident solar radiation (100s-1000s nm) greatly exceeds the built-in field and carrier diffusion length (~10s nm). To improve efficiency, research has largely been directed toward nanosizing the active material morphology and introducing midgap electronic states to increase optical absorption. Plasmonically enhanced PEC using Au nanostructures has also been recently demonstrated, though the overall increase in efficiency has been low due to poor optical characteristics of Au in the blue and UV portion of the solar spectrum.
Our work focuses on developing low cost Al nanostructures to substantially increase the spatial overlap between the incident optical field and the active water splitting material. Nanoimprint lithography was used to produce large area Al gratings which were then coated with TiO2 by sputtering, followed by annealing at 400 °C. Light of AM 1.5G was illuminated on the nanostructured electrode for photocurrent measurement.