WO₃−Fe₂O₃Photoanodes for Water Splitting: A Host Scaffold, Guest Absorber Approach

Abstract

Solar hydrogen production via watersplitting with hematite (Fe 2 O 3 ) has been limited by poor light absorption and a small hole diffusion length. These drawbacks can be overcome by using a high-surface-area host to support a thin layer of hematite—allowing photogenerated holes to be produced in high proximity to the semiconductor-liquid junction. Here we demonstrate the effectiveness of this concept using a nanostructured host scaffold (WO 3 ) prepared by atmospheric pressure CVD to support a thin layer of Fe 2 O 3 nanoparticles deposited by a similar method. A 20% increase in the photocurrent was observed in host−guest electrodes as compared to control films with the same amount of hematite (equivalent to a 60 nm film) deposited without the host scaffold. The improvement is attributed to an increase in the absorbed photon conversion efficiency (APCE), especially for longer wavelengths where the photon penetration depth is large in hematite. For light with a wavelength of 565 nm, the APCE improves to 8.0%, as compared to 5.7% with the control films because of the host/guest architecture.