Facet-Dependent Kinetics and Energetics of Hematite for Solar Water Oxidation Reactions

Wei Li, Ke R. Yang, Xiahui Yao, Yumin He, Qi Dong, Gary W Brudvig, Victor S. Batista, Dunwei Wang

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

The performance of a photoelectrochemical (PEC) system is highly dependent on the charge separation, transport and transfer characteristics at the photoelectrode|electrolyte interface. Of the factors that influence the charge behaviors, the crystalline facets of the semiconductor in contact with the electrolyte play an important role but has been poorly studied previously. Here, we present a study aimed at understanding how the different facets of hematite affect the charge separation and transfer behaviors in a solar water oxidation reaction. Specifically, hematite crystallites with predominantly {012} and {001} facets exposed were synthesized. Density functional theory (DFT) calculations revealed that hematite {012} surfaces feature higher OH coverage, which was confirmed by X-ray photoelectron spectroscopy (XPS). These surface OH groups act as active sites to mediate water oxidation reactions, which plays a positive role for the PEC system. These surface OH groups also facilitate charge recombination, which compromises the charge separation capabilities of hematite. Indeed, intensity modulated photocurrent spectroscopy (IMPS) confirmed that hematite {012} surfaces exhibit higher rate constants for both charge transfer and recombination. Open circuit potential (OCP) measurements revealed that the hematite {012} surface exhibits a greater degree of Fermi level pinning effect. Our results shed light on how different surface crystal structures may change surface kinetics and energetics. The information is expected to contribute to efforts on optimizing PEC performance for practical solar fuel synthesis.

Original languageEnglish
Pages (from-to)5616-5622
Number of pages7
JournalACS Applied Materials and Interfaces
Volume11
Issue number6
DOIs
Publication statusPublished - Feb 13 2019

Keywords

  • energetics
  • facet
  • hematite
  • kinetics
  • photoelectrochemistry
  • water splitting

ASJC Scopus subject areas

  • Materials Science(all)

Fingerprint Dive into the research topics of 'Facet-Dependent Kinetics and Energetics of Hematite for Solar Water Oxidation Reactions'. Together they form a unique fingerprint.

  • Cite this