Page 82 - Multifunctional Photocatalytic Materials for Energy

Energy band engineering of metal oxide for enhanced visible light absorption 71

e –
O 2
e –
e –
e –
H
H
E + \H 2 2
h +
E O 2\ H 2 O h +
h +
Pt
Photoanode PV I PV II
(A) e –

p-type n-type
e –
e –
H
E + \H 2 E F
h + Photocathode (a-Si)
E O 2\ H 2 O Photoanode (Fe 2 O 3 )

h +

(B) Ohmic contact
Potential II
(V vs. NHE) –
pH7 hv > E g e –
I C.B. e
+
(H /H ) hv > E H
–0.41 2 g e – e – E g 2
C.B. Red H +
(Ox/Red) H O V.B.
2
+0.82 E g Ox e – h +
(O /H O) O 2 e – V.B. H 2 evolution
2
2
photocatalyst
h +
O evolution
2
(C) photocatalyst
Fig. 4.13 Configurations, electronic band alignment, and each function in a multifunctional
system for overall water splitting to chemical fuels. (A) PV/PEC tandem configuration, (B)
Photoanode/Photocathode tandem PEC cell, and (C) Z-scheme systems.
Reproduced with permissions from K. Zhang, M. Ma, P. Li, D.H. Wang, J.H. Park, Water
splitting in tandem devices: moving photolysis beyond electrolysis, Adv. Energy Mater. 6
(2016) 1600602; J. Jang, C. Du, Y. Ye, Y. Lin, X. Yao, J. Thorne, E. Liu, G. McMahon, J.
Zhu, A. Javey, J. Guo, D. Wang, Enabling unassisted solar water splitting by iron oxide and
silicon. Nat. Commun. 6 (2015) 8447; J. Brillet, J. Yum, M. Cornuz, T. Hisatomi, R. Solarska,
J. Augustynski, M. Graetzel, K. Sivula, Highly efficient water splitting by a dual-absorber
tandem cell, Nat. Photonics 6 (2012) 824–828; K. Maeda, K. Domen, Photocatalytic water
splitting: recent progress and future challenges, J. Phys. Chem. Lett. 1 (2010) 2655–2661.
Copyright © Wiley & Sons, Nature Publishing group and the American Chemical Society.