Au nanoslit arrays as plasmonic substrates for solar water splitting with α-Fe2O3

Bohn, Christopher; Agrawal, Amit; Lee, Youngmin; Esposito, Daniel; Kinney, Robert; Xu, Ting; Walter, Erich; Talin, Albert; Lezec, Henri; Szalai, Veronika


We investigate plasmonic enhancement of water splitting using gold nanoslit arrays coated with thin (<100 nm) layers of α‑Fe2O3. By optimizing the diameter, period and thickness of the nanoslits, we measure photocurrent enhancements of a factor of ≈2 under illumination with 532 nm light in an electrolyte of 1 M NaOH.  Two control experiments show that this enhancement is a result of surface plasmon polaritons and not due to increased surface area.  Identical nanoslit arrays fabricated from Pt, a lossy metal at 532 nm, and Au nanoslit arrays illuminated with light below the cut-off wavelength for Au surface plasmon polaritons (325 nm) both show negligible enhancement. Finally, we discuss results for the Au/α-Fe2O3 system and provide general recommendations for achieving plasmonic enhancement in wide bandgap semiconductor systems.