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Compared with stable-phase hexagonal CdS, the metastable cubic CdS photocatalyst usually shows a lower H 2 -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 H 2 -evolution activity has seldom been concerned. In this study, a direct precipitation method in a sulfur-rich Na 2 S–Na 2 SO 3 system has been developed to prepare the suspensible cubic-phase CdS nanocrystal ( c -CdS-NC) photocatalyst with a high H 2 -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 m 2 /g) exhibits a stable and suspensible photocatalysts due to the massive and preferential adsorption of S 2– /SO 3 2– ions on the nanocrystal surface. Photocatalytic results indicated that the suspensible c -CdS-NC photocatalysts clearly exhibited an obviously higher H 2 -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 S 2– /SO 3 2– -mediated mechanism was proposed for the enhanced H 2 -evolution performance of the suspensible c -CdS-NC, namely the massive adsorbed S 2– 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 H 2 -evolution reaction. The present work may provide important insights for developing high-performance photocatalytic materials.
Yu et al. (Thu,) studied this question.