Bismuth oxychloride hollow microspheres with high visible light photocatalytic activity

Hollow microspheres of two bismuth oxychlorides, BiOCl and Bi₂₄O₃₁Cl₁₀, were successfully synthesized using carbonaceous microsphere sacrificial templates. The phase evolution from BiOCl to Bi₂₄O₃₁Cl₁₀ was easily realized by heating the former at 600 ℃. With a uniform diameter of about 200 nm, an average shell thickness of 40 nm, and basic nanosheets of < 20 nm, the hollow microspheres of both BiOCl and Bi₂₄O₃₁Cl₁₀ showed high visible light photocatalytic activity towards the degradation of Rhodamine B (RhB). Besides the effective photosensitization process and efficient photointroduced carrier separation, the high photocatalytic activity was believed to result from their hollow-structure-dependent large visible light absorption. Moreover, as a chlorine-deficient analogue, the Bi₂₄O₃₁Cl₁₀ hollow spheres possessed a narrower band gap, more dispersive band structure, and higher photocarrier conversion efficiency, which further helped them to exhibit better photocatalytic activity.