Suspensible Cubic-Phase CdS Nanocrystal Photocatalyst: Facile Synthesis and Highly Efficient H2-Evolution Performance in a Sulfur-Rich System

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.