Decoupling Feature Size and Functionality in Solution-Processed, Porous Hematite Electrodes for Solar Water Splitting

• Published in: Nano letters Vol. 10; no. 10; pp. 4155 - 4160
• Main Authors: Brillet, Jeremie, Grätzel, Michael, Sivula, Kevin
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 13-10-2010
• Subjects: Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Low-dimensional structures (superlattices, quantum well structures, multilayers): structure, and nonelectronic properties; Physics; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); nanostructured electrodes; mesoporous silica; Iron oxide; sintering; confinement; photoelectrochemical energy storage; Encapsulation; Hematite; Confinement; Particle size; Annealing; Porous electrode; Porous materials; Photocurrents; Nanostructures; Quantum yield; Heat treatments; Calcium nitride; Silicon oxides; Beryllium; Illumination; Electrolytes; Oxidation; Photoconductivity
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/nl102708c

We introduce a simple solution-based strategy to decouple morphological and functional effects of annealing nanostructured, porous electrodes by encapsulation with a SiO2 confinement scaffold before high temperature treatment. We demonstrate the effectiveness of this approach using porous hematite (α-Fe2O3) photoanodes applied for the storage of solar energy via water splitting and show that the feature size and electrode functionality due to dopant activation can be independently controlled. This allows a significant increase in water oxidation photocurrent from 1.57 mA cm−2 (in the control case) to 2.34 mA cm−2 under standard illumination conditions in 1 M NaOH electrolytethe highest reported for a solution-processed hematite photoanode. This increase is attributed to the improved quantum efficiency, especially with longer wavelength photons, due to a smaller particle size, which is afforded by our encapsulation strategy.