Tuning the morphology and structure of disordered hematite photoanodes for improved water oxidation: a physical and chemical synergistic approach

Guanyu Liu, Siva Krishna Karuturi, Hongjun Chen, Leone Spiccia, Hark Hoe Tan, Chennupati Jagadish, Dunwei Wang, Alexandr N. Simonov, Antonio Tricoli

Research output: Contribution to journalArticleResearchpeer-review

6 Citations (Scopus)

Abstract

Design of efficient photoelectrodes for water oxidation requires careful optimization of the morphology and structure of a photoactive material to maximize electrical conductivity and balance carrier diffusion length with light penetration depth. Hematite-based photoanodes can theoretically oxidize water at very high rates, as provided by the optimal band-gap, but their performance is limited by the poor charge transport and low charge separation efficiency. Herein, we have developed physically- and chemically-induced morphological and structural tuning procedures, viz. capillary-force-induced self-assembly and corrosion followed by regrowth, which enable significant improvements in the performance of the hematite photoanodes. Specifically, a 24-fold enhancement in the photocurrent density for water oxidation (1 M NaOH) at 1.23 V vs. reversible hydrogen electrode under simulated 1 sun (100 mW cm–2, AM1.5G solar spectrum) irradiation has been achieved. The capillary-force-induced self-assembly improves the crystallinity, promotes preferential orientation of the hematite along the [110] direction, and thereby enhances the electrical conductivity of the material. Subsequent dissolution and regrowth of the hematite nanostructures provide higher light absorption, improve photo-generated charge separation and facilitate photoelectrocatalytic kinetics resulting in the significantly higher photoelectrocatalytic activity. These broadly applicable insights provide a robust set of guidelines for the engineering of efficient photoelectrodes initially made of disordered structures for conversion of solar energy into renewable fuels.

Original languageEnglish
Pages (from-to)745-752
Number of pages8
JournalNano Energy
Volume53
DOIs
Publication statusPublished - 1 Nov 2018

Keywords

  • Capillary force
  • Hematite
  • Morphological and structural tuning
  • Nanostructures
  • Photoelectrochemical water oxidation
  • Self-assembly

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