Gram-scale batch production of novel CdS hollow hexagonal prisms by a molten salt method and the improved photocatalytic stability

• CdS hollow hexagonal prisms are prepared firstly. • Molten KSCN could act as sulfur source, reaction medium and morphology control agent. • The novel hollow hexagonal prisms morphology can be attributing to Pearson's Hard-Soft-Acid-Base theory. • CdS hollow hexagonal prisms shows an outstanding cycle stability. Molten salt method can be applied to produce CdS with desirable stability on a massive scale. It remains a significant challenge to obtain CdS photocatalysts with high stability on a large scale. In this work, CdS are prepared using a simple KSCN molten salt method (CdS-MS) and conventional hydrothermal method (CdS-HT), respectively. CdS-MS consists of novel hollow hexagonal prisms, which is not reported so far. Under visible light irradiation (λ > 400 nm), CdS-MS shows a higher photocatalytic activity for the degradation of phenol, norfloxacin and RhB, which are 2.27, 2.11 and 1.05 times higher than CdS-HT. The higher photocatalytic activity of CdS-MS is mainly attributed to the novel hollow hexagonal prism microstructure and more sulfur defects, leading to the greater oxidation potential and higher charge separation efficiency. Furthermore, CdS-MS shows outstanding cycle stability. After four cycles, 90.6% of the degradation efficiency is retained for CdS-MS, while only 68.3% of the degradation efficiency is retained for CdS-HT. The higher stability of CdS-MS is mainly attributed to its unique morphology and surface valence of sulfur, which make it more difficult to agglomerate and occur photocorrosion, respectively. The reported method is simple and high-yielding, which is easy to extend to mass production.