Photocatalytic Hydrogen Evolution over Tantalate Photocatalysts
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0974-CC09-06
Photocatalytic Hydrogen Evolution over Tantalate Photocatalysts Jaturong Jitputti, Sorapong Pavasupree, Yoshikazu Suzuki, and Susumu Yoshikawa Molecular Assemblies Design Research Section, Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto, 611-0011, Japan
ABSTRACT Strontium tantalate-strontium titanate composite photocatalysts were prepared by solidstate reaction at 1273 K using SrCO3, Ta2O5, and TiO2 as starting materials. The prepared solid photocatalysts were characterized using XRD and UV-vis spectroscopy analyses. These prepared tantalate and titanate photocatalysts showed high photocatalytic H2 evolution activity by water splitting without co-catalyst loading. The highest H2 evolution rate of prepared photocatalysts was found to be 138 µmolh-1 with the starting materials ratio of 2/0.5/1.5 (Sr/Ta/Ti; mol). Furthermore, this photocatalyst showed photocatalytic activity for H2 evolution from distilled water. INTRODUCTION Much attention has been paid to the photocatalytic decomposition of water into H2 and O2 over semiconductor materials since the first invention of photochemical water splitting proposed by Fujishima and Honda [1]. Hydrogen is recognized as an environmental friendly and a highefficiency fuel, since water and sunlight are renewable and cheap resources, the utilization of conversion capability from solar energy to chemical energy of the photocatalyst to produce H2 is quite promising way for clean energy development. There has been a remarkable progress in past decades for photocatalysts working under ultra-violet light (UV) and visible light irradiation [212]. A variety of photocatalysts, mainly Ti-, Sr-, Ta-based oxides have been reported to be effective for the photocatalytic decomposition of water [4-12]. Many types of photocatalyst based on these materials have been studies extensively. Among them, La-doped NiO/NaTaO3 [8,9] shows the highest photocatalytic decomposition of distilled water under UV irradiation, where as in case of visible light, Rh-doped SrTiO3 [11] shows very high activity for aqueous methanol solution. These has led us to test the photocatalytic activity of tantalate and titanate photocatalysts prepared from Sr-, Ta-,Ti- based oxides materials. In the present work, the effect of starting materials ratio (SrCO3, TiO2, and Ta2O5) of strontium tantalate-strontium titanate composite photocatalysts prepared by conventional solidstate reactions (SSR) was investigated in order to develop new active photocatalysts for H2 evolution under UV and visible light irradiation. Moreover, the effect of NiO doping was also investigated using Sr2Ta2O7, Sr5Ta4O15-SrTiO3 composite photocatalyst, which showed the highest among the prepared photocatalysts tested in this study.
EXPERIMENTAL PROCEDURE Tantalate photocatalysts were prepared by SSR method. The starting materials (TiO2 (Ishihara ST-01; 99.9%), SrCO3 (Wako pure chemical; 95%), Ta2O5 (Aldrich; 99.9%) were mixed at once according to the ratio of 2/x/ 2-x (Sr/Ta/Ti; mol) using the ball-milling method. The m
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