Enhancing Solar-Driven Water Splitting with
Surface-Engineered Nanostructures
Shaohua Shen,* Sarah A. Lindley, Chung-Li Dong, Eefei Chen, Ying-Rui Lu,
Jigang Zhou, Yongfeng Hu, Damon A. Wheeler, Penghui Guo, Jin Z. Zhang,
David S. Kliger, and Samuel S. Mao
Functional nanoscale interfaces that promote the transport of photoexcited
charge carriers are fundamental to efficient hydrogen production during
photoelectrochemical (PEC) splitting of water. Here, the realization of a
functional one-dimensional nanostructure achieved through surface engineer-
ing of hematite (α-Fe
2
O
3
) nanorods with a TiO
2
overlayer is reported. The
surface-engineered hematite nanostructure exhibits significantly improved
PEC performance as compared to untreated α-Fe
2
O
3
, with an increase in the
maximum incident photon-to-current efficiency (IPCE) of nearly 400% at
350 nm. While addition of the TiO
2
overlayer did not alter the lifetime of
photoexcited charge carriers, as evidenced from transient absorption spec-
troscopy, it is found that the presence of TiO
2
could enhance oxygen
electrocatalysis by interfacial electron enrichment, largely attributed to
enhanced O(2p)Fe(3d) hybridization. Moreover, the interfacial electronic
structure revealed from XANES measurements of the α-Fe
2
O
3
/TiO
2
nanorods
suggests that photoexcited holes in α-Fe
2
O
3
may efficiently transfer through
the TiO
2
overlayer to the electrolyte while electrons migrate to the external
circuit along the one-dimensional nanorods, thereby promoting charge
separation and enhancing PEC splitting of water.
1. Introduction
Hematite (α-Fe
2
O
3
) has been considered as a
promising photoelectrode material for solar
water splitting due to its stability, non-toxicity,
and earth-abundance.
[1–4]
Although the
bandgap of hematite (1.9–2.2 eV) is favorable
for efficient utilization of the majority of solar
photons, the solar-to-chemical energy con-
version efficiency achieved so far
[1–3]
is
significantly lower than that predicted by
theory in an ideal tandem photoelectrochem-
ical (PEC) configuration (up to 16%).
[5]
A
number of factors are responsible for the
limited PEC performance of α-Fe
2
O
3
, includ-
ing short hole diffusion length, fast charge
recombination dynamics, and sluggish oxy-
gen evolution kinetics.
[1,6]
In order to promote charge transfer and
charge separation of photogenerated car-
riers, numerous studies have focused on
improving the conductivity of α-Fe
2
O
3.
Doping has been a common approach,
using metals like Ti, Zr, Sn, Si, and Pt as
electron donors to enhance electrical
Prof. S. Shen, P. Guo
International Research Center for Renewable Energy
State Key Laboratory of Multiphase Flow in Power Engineering
Xi’an Jiaotong University
Shaanxi 710049, China
E-mail: shshen_xjtu@mail.xjtu.edu.cn
S. A. Lindley, E. Chen, Dr. D. A. Wheeler, Prof. J. Z. Zhang, Prof. D. S.
Kliger
Department of Chemistry and Biochemistry
University of California at Santa Cruz
Santa Cruz, CA 95064, United States
Prof. C.-L. Dong, Y.-R. Lu
Department of Physics
Tamkang University
151 Yingzhuan Road, New Taipei City 25137, Taiwan
Prof. J. Zhou, Prof. Y. Hu
Canadian Light Sources Inc.
44 Innovation Boulevard, Saskatoon, S7N 2V7, Canada
The ORCID identification number(s) for the author(s) of this article
can be found under https://doi.org/10.1002/solr.201800285.
DOI: 10.1002/solr.201800285
Prof. S. S. Mao
Department of Mechanical Engineering
University of California at Berkeley
Berkeley, CA 94720, United States
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