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Efficient Solar to Hydrogen Conversion from Neutral Electrolytes using Morphology-Controlled Sb2Se3 Light Absorber Jaemin Park, Wooseok Yang, Yunjung Oh, Jeiwan Tan, Hyungsoo Lee, Ramireddy Boppella, and Jooho Moon ACS Energy Lett., Just Accepted Manuscript • DOI: 10.1021/acsenergylett.8b02323 • Publication Date (Web): 22 Jan 2019 Downloaded from http://pubs.acs.org on January 24, 2019
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ACS Energy Letters
Efficient Solar to Hydrogen Conversion from Neutral Electrolytes using Morphology-Controlled Sb2Se3 Light Absorber Jaemin Park, Wooseok Yang, Yunjung Oh, Jeiwan Tan, Hyungsoo Lee, Ramireddy Boppella and Jooho Moon* Department of Materials Science and Engineering, Yonsei University, Seoul 03722, Republic of Korea Corresponding Author *E-mail:
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ABSTRACT
We present a novel solution-based synthesis method enabling the morphology variation of Sb2Se3 light absorbers. The morphology of Sb2Se3 films varies from dense particulate planar films to 1dimensional nanowire-stacked films upon modulating the Sb and Se molar ratio in the precursor ink. The effect of morphology and crystallographic orientation on the electrical and consequently the PEC properties of Sb2Se3-based photocathodes are investigated. Sequential deposition of CdS as a buffer layer with TiO2 and Pt enables us to build a favorable band structure. An onset potential of 0.47 V versus reversible hydrogen electrode (RHE) is observed with 13.5 mA cm–2 at 0 V versus RHE under air mass 1.5 global illumination in a pH 1 electrolyte. In addition, the surface-modified photocathode stably produces hydrogen with a photocurrent of 11 mA cm–2 at 0 V versus RHE in a neutral electrolyte, thus demonstrating the promising potential of the proposed Sb2Se3 photocathodes as efficient PEC water-splitting devices.
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ACS Energy Letters
TOC GRAPHICS
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Fossil fuels can hardly meet the world’s rapidly increasing energy demands because of their limited supply and inevitable carbon dioxide emissions during their combustion. In recent times, solar power is receiving particular attention as a source of carbon-free, abundant, and clean energy.1,2 For its effective harvesting and utilization, photoelectrochemical (PEC) splitting of water into hydrogen and oxygen is considered a sustainable solution; in this technique, water splitting occurs through direct conversion over a simple photoelectrode.3-7 When the photoelectrode is immersed in an electrolyte and irradiated by sunlight, the PEC water splitting reaction occurs in the following sequential steps. 1) Charge generation by light absorption, 2) separation of the photo-generated electrons and holes, and 3) charge transfer from the semiconductor to the electrolyte. To achieve a high solar-to-hydrogen (STH) efficiency in these steps, the semiconductor used in the PEC water-splitting device should be capable of absorbing a sufficient amount of light to create charge carriers; further, they should be transported to the electrolyte where the electrochemical reaction occurs. Among these steps, charge transport through the semiconductor plays an important role because the photo-generated charge carriers (electrons for photocathode) might undergo recombination if the excited charges are not effectively separated and transported to the semiconductor/electrolyte interface.8,9 For example, high STH efficiencies approaching 20% were achieved with photoelectrodes based on high-quality group III–V semiconductors (e.g., GaAs, GaInP2, etc.),10–12 due to a high mobility of 8500 cm2 V–1 s–1.13 However, metal oxides with poor charge-trans owing to which it is port properties (i.e., mobilities of BiVO3 and Fe2O3 are in the range of 0.01–0.1 cm2 V–1 s–1)14–16 exhibit moderate STH efficiencies (
