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Ga2O3/TiO2 semiconductors free of noble metals for the photocatalytic hydrogen production in a water/methanol mixture

Navarrete, Michelle, Cipagauta‐Díaz, Sandra, Gómez, Ricardo
Journal of chemical technology and biotechnology 2019 v.94 no.11 pp. 3457-3465
Fourier transform infrared spectroscopy, X-ray diffraction, adsorption, hydrogen, hydrogen production, irradiation, metals, methanol, nitrogen, photocatalysis, photocatalysts, photoluminescence, potential energy, reflectance, reflectance spectroscopy, scanning electron microscopy, semiconductors, sol-gel processing, titanium dioxide, ultraviolet radiation
BACKGROUND: Hydrogen gas (H₂) has been identified as a potential energy source to reduce the dependence on fossil fuels. Titanium dioxide (TiO₂) semiconductor has been widely used in photocatalysis. Doping of different semiconductor oxides into TiO₂ has been documented to enhance its photocatalytic activity. In the present work, β‐Ga₂O₃/TiO₂ (TG) photocatalysts for H₂ production by water/methanol mixture decomposition have been synthesized by the sol–gel method varying the β‐Ga₂O₃ content (3%, 5% and 10% w/w). The catalysts were characterized by X‐ray diffraction, nitrogen adsorption, ultraviolet (UV)‐visible diffuse reflectance, Fourier‐transform infrared spectroscopy, scanning electron microscopy and photoluminescence analysis. RESULTS: An excellent activity for H₂ production under UV light (I₀ = 2.0 mW cm–², λ = 254 nm) was detected in TG composites. Experimental results indicated that the maximum H₂ production rate was 1217 µmol g⁻¹ during 5 h of reaction and the TG5 photocatalyst was observed to have a higher activity for photocatalytic H₂ evolution than pure Ga₂O₃ and Pt/TiO₂ (TPt) test material. Moreover, a possible mechanism of charge separation in the composite under UV light irradiation was proposed. CONCLUSIONS: The H₂ improved activity of TG5 can be attributed to low charge recombination of the e⁻‐h⁺ pairs that improves the interfacial charge transfer, which is in agreement with the photoluminescence study. © 2019 Society of Chemical Industry