A series of BiOCl/SnO ₂ heterojunctions exhibiting exceptional visible light photocatalytic performance has been successfully prepared using a two-step solution route.

This work reports on the construction of a Bi₂₄O₃₁Cl₁₀/BiOCl heterojunction via a simple thermal annealing method. The X-ray diffraction (XRD) results indicated that the phase transformation from BiOCl to Bi₂₄O₃₁Cl₁₀ could be realized during the thermal annealing process. The high-resolution transmission electron microscopy (HRTEM) images, X-ray photoelectron spectroscopy (XPS) binding energy shifts, Raman spectra and Fouier transform infrared spectroscopy (FT-IR) spectra confirmed the formation of the Bi₂₄O₃₁Cl₁₀/BiOCl heterojunction. The obtained Bi₂₄O₃₁Cl₁₀/BiOCl photocatalyst showed excellent conversion efficiency and selectivity toward photocatalytic conversion of benzyl alcohol to benzaldehyde under visible light irradiation. The radical scavengers and electron spin resonance (ESR) results suggested that the photogenerated holes were the dominant reactive species responsible for the photocatalytic oxidation of benzyl alcohol and superoxide radicals were not involved in the photocatalytic process. The in-situ generation of Bi₂₄O₃₁Cl₁₀/BiOCl heterojunction may own superior interfacial contact than the two-step synthesized heterojunctions, which promotes the transfer of photogenerated charge carriers and is favorable for excellent photocatalytic activities.

This work explores a hydrothermal route to synthesis of self-doped SiO₂/SnO₂/SnO₂:Sn²⁺ nanostructures with controlled hierarchical structures and lattice parameters for tunable optical and photocatalytic properties. The effects of Sn²⁺ self-doping in the SnO₂ lattice on the local structure, electronic structure, and photodegradation of methyl orange were systematically investigated. It is found that two layers of SnO₂ and SnO₂:Sn²⁺ nanocrystals with thicknesses of 13 and 8 nm were coated on SiO₂ spheres showing monodispersed features. By Sn²⁺ doping, a blue shift of the Sn 3d XPS binding energy was observed, which is thought to be mainly related to the difference in electronegativity of Sn⁴⁺, Sn²⁺ and variation of lattice parameters. In contradiction to the quantum size effect, the self-doped SiO₂/SnO₂/SnO₂:Sn²⁺ nanostructures showed an abnormal red shift of band gap energy, which is related to doping effects and variations of lattice parameters. With well-defined lattice structure and electronic structure, the photocatalytic performance of SiO₂/SnO₂/SnO₂:Sn²⁺ nanostructures can be well regulated and optimized.