Photocatalytic hydrogen production on chemically etched strontium titanate surfaces
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Photocatalytic hydrogen production on chemically etched strontium titanate surfaces Burcu Oral1 · Dilara Saadetnejad1 · Ramazan Yıldırım1 Received: 23 July 2020 / Accepted: 16 September 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract This work aims to investigate the photocatalytic hydrogen evolution over acid (citric acid and hydrochloric acid) etched strontium titanate (SrTiO3), which is promoted by 1 wt% platinum (Pt) as co-catalyst. Scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and ultraviolet–visible spectroscopy (UV–Vis) analyses of the un-etched and etched SrTiO3 are presented; the results indicate that etching affects the surface structure while it does not change the bulk properties of semiconductor. The results of the photocatalytic activity tests performed in a methanol solution using a semi-batch reaction system equipped with argon flow to collect hydrogen, 300 W xenon lamp as light source and gas chromatograph for the analysis, are also reported. The etching with 4 mol L −1 citric acid increases the hydrogen evolution rate about 20% while the highest rate of hydrogen production over etched Pt-SrTiO3 is about 550 µmol/gcat.h at the 6 h of the reaction test. Keywords Water splitting · Hydrogen evolution · Perovskites · SrTiO3 · Wet chemical etching · Citric acid
Introduction The demand for renewable and sustainable energy has been increased in recent years due to the increasing world population, depletion of fossil fuels and growing concerns for environment; the conversion of solar radiation into another energy forms like electricity (through photovoltaic panels) or chemical energy through the production of solar fuels (like hydrogen from water) may be among the potential solutions for meeting the energy needs of the future [1, 2]. The research for solar driven water splitting for hydrogen production reached a turning point by the work of Fujishima and Honda reporting the hydrogen production in a photo-electrochemical cell in * Ramazan Yıldırım [email protected] 1
Department of Chemical Engineering, Boğaziçi University, İstanbul, Turkey
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Reaction Kinetics, Mechanisms and Catalysis
1972 [3]. Later, the photocatalytic water splitting over the particulate photocatalysts was also achieved by Lehn et al., Sato and White, and Domen et al. in 1980 [4]. Since then, both the photoelectrochemical cells and the particulate photocatalysts have been investigated extensively using various photocatalytic materials. A photocatalyst usually consists of a light absorber semiconductor and co-catalyst for oxidation and/or a reduction [5]. To be effective in solar water splitting, the band gap energy of the semiconductor should be suitable for the absorption of visible light; the conduction band edge should be also above the redox potential of hydrogen while the valence band edge should be lower than oxidation potential of water [6]. Metal oxide semiconductors such as TiO2, ZnO, CeO2, SnO2 and ZrO2 have been empl
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