HgI₂: A novel photocatalyst with high performance in degradation of rhodamine B dyes under visible-light irradiation

A new photocatalyst, HgI₂, was successfully developed. The HgI₂ sample was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), ultraviolet–visible diffuse reflectance spectrum (UV–vis DRS) and photoluminescence (PL) techniques. Its activity is as high as that of the highly efficient photocatalyst Ag₃PO₄ in degradation of rhodamine B (RhB) dyes under irradiation of visible light. It can be reused for at least three cycles without obvious loss of its activity in the degradation experiments. The main active species of HgI₂ for the RhB degradation are superoxide anion radicals. The high photocatalytic activity of HgI₂ may be attributed to its low recombination rate of the photogenerated carriers. - Highlights: • A new photocatalyst, HgI₂, was successfully developed. • Photocatalytic activity of HgI₂ is as high as that of Ag₃PO₄. • HgI₂ can be reused for at least three cycles without obvious loss of its activity. • The high activity may be due to low recombination rate of photogenerated carriers.