**Plasmonic Ag Nanoparticle-Loaded n-p Bi2O2CO3/**α**-Bi2O3 Heterojunction Microtubes with Enhanced Visible-Light-Driven Photocatalytic Activity**

**Haibin Li 1,2, Xiang Luo 1, Ziwen Long 1, Guoyou Huang 1 and Ligang Zhu 2,\***


**Abstract:** In this study, n-p Bi2O2CO3/α-Bi2O3 heterojunction microtubes were prepared via a onestep solvothermal route in an H2O-ethylenediamine mixed solvent for the first time. Then, Ag nanoparticles were loaded onto the microtubes using a photo-deposition process. It was found that a Bi2O2CO3/α-Bi2O3 heterostructure was formed as a result of the in situ carbonatization of α-Bi2O3microtubes on the surface. The photocatalytic activities of α-Bi2O3 microtubes, Bi2O2CO3/<sup>α</sup>-Bi2O3 microtubes, and Ag nanoparticle-loaded Bi2O2CO3/α-Bi2O3 microtubes were evaluated based on their degradation of methyl orange under visible-light irradiation (λ > 420 nm). The results indicated that Bi2O2CO3/α-Bi2O3 with a Bi2O2CO3 mass fraction of 6.1% exhibited higher photocatalytic activity than α-Bi2O3. Loading the microtubes with Ag nanoparticles significantly improved the photocatalytic activity of Bi2O2CO3/α-Bi2O3. This should be ascribed to the internal static electric field built at the heterojunction interface of Bi2O2CO3 and α-Bi2O3 resulting in superior electron conductivity due to the Ag nanoparticles; additionally, the heterojunction at the interfaces between two semiconductors and Ag nanoparticles and the local electromagnetic field induced by the surface plasmon resonance effect of Ag nanoparticles effectively facilitate the photoinduced charge carrier transfer and separation of α-Bi2O3. Furthermore, loading of Ag nanoparticles leads to the formation of new reactive sites, and a new reactive species ·O2<sup>−</sup> for photocatalysis, compared with Bi2O2CO3/α-Bi2O3.

**Keywords:** α-Bi2O3; Bi2O2CO3; silver; heterojunction; microtube; photocatalysis
