Suspensible Cubic-Phase CdS Nanocrystal Photocatalyst: Facile Synthesis and Highly Efficient H2-Evolution Performance in a Sulfur-Rich System
2018
Compared with stable-phase hexagonal CdS, the metastable cubic CdS photocatalyst usually shows a lower H₂-evolution performance under visible-light irradiation. Thus, the widely reported high-performance CdS photocatalysts are mainly focused on the hexagonal phase, while the cubic-phase CdS with a high H₂-evolution activity has seldom been concerned. In this study, a direct precipitation method in a sulfur-rich Na₂S–Na₂SO₃ system has been developed to prepare the suspensible cubic-phase CdS nanocrystal (c-CdS-NC) photocatalyst with a high H₂-evolution activity. In this case, the resultant c-CdS-NC with a small crystal size (ca. 5 nm) and high specific surface area (>75.23 m²/g) exhibits a stable and suspensible photocatalysts due to the massive and preferential adsorption of S²–/SO₃²– ions on the nanocrystal surface. Photocatalytic results indicated that the suspensible c-CdS-NC photocatalysts clearly exhibited an obviously higher H₂-evolution performance (0.36 mmol h–¹) than the traditional hexagonal CdS (0.14 mmol h–¹) by a factor of 2.6 times. Based on the present results, a S²–/SO₃²–-mediated mechanism was proposed for the enhanced H₂-evolution performance of the suspensible c-CdS-NC, namely the massive adsorbed S²– ions on the suspensible c-CdS-NC surface not only promote the rapid capture of photogenerated holes but also can work as the effective active sites for H₂-evolution reaction. The present work may provide important insights for developing high-performance photocatalytic materials.
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