Nanoscale PAPER Cite this: Nanoscale, 2019, 11, 109 Received 13th October 2018, Accepted 2nd December 2018 DOI: 10.1039/c8nr08292h rsc.li/nanoscale Direct Z scheme-fashioned photoanode systems consisting of Fe 2 O 3 nanorod arrays and underlying thin Sb 2 Se 3 layers toward enhanced photoelectro- chemical water splitting performance† Aizhen Liao, a,b Yong Zhou, * a,b,c Leixin Xiao, d Chunfeng Zhang, b Congping Wu, a,b,c Adullah M. Asiri, e Min Xiao b and Zhigang Zou a,b,d,c An elegant Z-scheme-fashioned photoanode consisting of Fe 2 O 3 nanorod arrays and underlying thin Sb 2 Se 3 layers was rationally constructed. The photocurrent density of the Sb 2 Se 3 –Fe 2 O 3 Z-scheme photoanode reached 3.07 mA cm -2 at 1.23 V vs. RHE, three times higher than that of pristine Fe 2 O 3 at 1.03 mA cm -2 . An obvious cathodic shift of the photocurrent onset potential of about 200 mV was also observed. The transient photovoltage response demonstrates that the suitable band edges (E CB ∼-0.4 eV and E VB ∼ 0.8 eV) of Sb 2 Se 3 , match well with Fe 2 O 3 (E CB ∼ 0.29 eV and E VB ∼ 2.65 eV), permitting the photoexcited electrons on the conduction band of the Fe 2 O 3 to transfer to the valence band of Sb 2 Se 3 , and recombine with the holes therein, thus allowing a high concentration of holes to collect in the Fe 2 O 3 for water oxidation. The transient absorption spectra further corroborate that the built-in electric field in the p–n heterojunction leads to a more effective separation and a longer lifetime of the charge carriers. Introduction Solar water splitting in photoelectrochemical (PEC) cells has drawn much attention for sustainable hydrogen production, owing to the limited reserve of fossil fuels and the increasing concern of environmental pollution. 1–3 Photoanodes for water oxidation are the rate-limiting step for the PEC overall water splitting efficiency. Hematite (α-Fe 2 O 3 ), an n-type semi- conductor with a suitable narrow band gap (2.2 eV), has emerged as one of the most attractive photoanode candidates because of its low cost, (photo)-electrochemical stability, non- toxicity, and earth-abundance. 4–7 However, α-Fe 2 O 3 suffers from sluggish water oxidation kinetics, severe surface recombi- nation, poor lifetimes of carriers, and short hole migration distance. 8–10 Great efforts such as surface passivation, nano- structure engineering, selective doping, and oxygen evolution cocatalysts have been made to improve its PEC performance. 11–15 However, the α-Fe 2 O 3 photoanode developed so far still shows a lower photocurrent density relative to its theoretical maximum of 12.6 mA cm -2 at 1.23 V versus the reversible hydrogen electrode (vs. RHE) under AM 1.5G illumi- nation (100 mW cm -2 ). 9,16 Obviously, a single Fe 2 O 3 com- ponent cannot satisfy the requirement of efficiently steering the spatial separation/transfer of electron–hole pairs for high PEC performance. The conjugation of coupling with other semiconductors has been proven an efficient method for solving the weaknesses above by providing a built-in electric field and optimal transportation path. 17 Type II hetero- structures have been commonly built, allowing photogenerated electrons (holes) to be transferred from one semiconductor with a higher conduction (lower valence) band (CB) to that with a lower conduction (higher valence) band (VB). 18 However, the redox ability of this type of heterojunction is dynamically lowered after charge flowing, compared to individ- ual components. Z-scheme photocatalyst systems by mimicking natural photosynthesis in green plants are designed to employ two semiconductors with one H 2 production photocatalyst and one O 2 production photocatalyst. 19 The Z-scheme semiconductor heterojunction possesses a vectorial charge transfer feature, † Electronic supplementary information (ESI) available. See DOI: 10.1039/ c8nr08292h a Eco-Materials and Renewable Energy Research Center (ERERC), Jiangsu Key Laboratory for Nano Technology, Nanjing University, Nanjing 210093, China. E-mail: zhouyong1999@nju.edu.cn b National Laboratory of Solid State Microstructures, Collaborative Innovation Center of Advanced Microstructures, School of Physics, Nanjing University, Nanjing 210093, P. R. China c Sunlite Ltc, Kunshan Innovation Institute of Nanjing University, Kunshan, Jiangsu 215347, P. R. China d School of Engineering and Applied Science, Nanjing University, Nanjing 210093, P. R. China e King Abdulaziz University, Chemistry Department, Faculty of Science, Jeddah 21589, Saudi Arabia This journal is © The Royal Society of Chemistry 2019 Nanoscale, 2019, 11, 109–114 | 109 Published on 03 December 2018. Downloaded on 1/21/2019 12:29:20 AM. View Article Online View Journal | View Issue