Visible-light-driven photocatalytic properties of layered double hydroxide supported-Bi2O3 modified by Pd(II) for methylene blue

• A new efficient visible light response photocatalyst was prepared by Bi2O3, LDHs and reduction cocatalysts Pd(II).
• Addition of LDHs promotes the Bi2O3 phase transformation from α-Bi2O3 to β-Bi2O3.
• Mechanism for photodegradation was proposed.

Bi2O3 on the Mg/Al layered double hydroxide (Bi2O3/LDH) was prepared by impregnation technique, its calcined product was reconstructed and modified with Pd(II) (Pd(II)-Bi2O3/RLDH), which was demonstrated as an efficient visible-light photocatalyst. XRD confirmed that the phase of loaded Bi2O3 transformed from α-Bi2O3 to β-Bi2O3 at 773 K calcination temperature. N2-adsorption/desorption, SEM and TEM displayed that the resulting Pd(II)-Bi2O3/RLDH composite possess high crystallinity, hierarchical structure as well as large specific surface area. EDX and ICP-AES were used to investigate the type and content of the elements in Pd(II)-Bi2O3/RLDH. UV–vis DRS confirmed that Pd(II)-Bi2O3/RLDH, with a low band gap of ∼2.19 eV, has a broad absorption in visible light region. The as-prepared Pd(II)-Bi2O3/RLDH displayed significant photocatalytic activity for the degradation of methylene blue (MB) under visible-light irradiation. Factors such as calcination temperature, LDH content and Pd (II) content were studied, which may affect the photodegradation of MB. The stability of the photocatalysts was comfirmed using reclaimed Pd(II)-Bi2O3/RLDH in four successive runs, demonstrating its great potential application in the field of photocatalysis. With the supports of the characterization analysis and experimental results, a reasonable mechanism of photocatalytic degradation of MB by Pd(II)-Bi2O3/RLDH was proposed.

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