In situ probe of photocarrier dynamics in water-splitting hematite (α-Fe2O3) electrodes

Zhuangqun Huang; Yongjing Lin; Xu Xiang; William Rodríguez-Córdoba; Kenneth J. McDonald; Karl S. Hagen; Kyoung-Shin Choi; Bruce S. Brunschwig; Djamaladdin G. Musaev; Craig L. Hill; Dunwei Wang; Tianquan Lian

doi:10.1039/C2EE22681B

In situ probe of photocarrier dynamics in water-splitting hematite (α-Fe₂O₃) electrodes†

Zhuangqun Huang,‡^a Yongjing Lin,^b Xu Xiang,^c William Rodríguez-Córdoba,^a Kenneth J. McDonald,^d Karl S. Hagen,^a Kyoung-Shin Choi,^d Bruce S. Brunschwig,^e Djamaladdin G. Musaev,^f Craig L. Hill,^a Dunwei Wang^b and Tianquan Lian*^a

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* Corresponding authors

^a Department of Chemistry, Emory University, Atlanta, Georgia 30322, USA
E-mail: tlian@emory.edu
Fax: +1 404 727 6586
Tel: +1 404 727 6649

^b Department of Chemistry, Merkert Chemistry Center, Boston College, 2609 Beacon Street, Chestnut Hill, Massachusetts 02467, USA

^c State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, PR China

^d Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, USA

^e Beckman Institute, California Institute of Technology, Pasadena, California, USA

^f Cherry L. Emerson Center for Scientific Computation, Emory University, Atlanta, Georgia 30322, USA

Abstract

The spectra and dynamics of photogenerated electrons and holes in excited hematite (α-Fe₂O₃) electrodes are investigated by transient absorption (from visible to infrared and from femto- to micro-seconds), bias-dependent differential absorption and Stark spectroscopy. Comparison of results from these techniques enables the assignment of the spectral signatures of photogenerated electrons and holes. Under the pulse illumination conditions of transient absorption (TA) measurement, the absorbed photon to electron conversion efficiency (APCE) of the films at 1.43 V (vs. reversible hydrogen electrode, RHE) is 0.69%, significantly lower than that at AM 1.5. TA kinetics shows that under these conditions, >98% of the photogenerated electrons and holes have recombined by 6 μs. Although APCE increases with more positive bias (from 0.90 to 1.43 V vs. RHE), the kinetics of holes up to 6 μs show negligible change, suggesting that the catalytic activity of the films is determined by holes with longer lifetimes.

Energy & Environmental Science

In situ probe of photocarrier dynamics in water-splitting hematite (α-Fe₂O₃) electrodes†

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In situ probe of photocarrier dynamics in water-splitting hematite (α-Fe₂O₃) electrodes

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