Porous peanut-like Bi ₂O ₃-BiVO ₄ composites with heterojunctions: One-step synthesis and their photocatalytic properties

For the first time, porous peanut-like Bi ₂O ₃- BiVO ₄ composites with heterojunctions have been synthesized by a one-step mixed solvothermal method with the assistance of a l-lysine template. A mixture of ethylene glycol (EG) and H ₂O (volume ratio of EG-H ₂O = 3:1) is used as the solvent. Unlike the traditional methods, no concentrated HNO ₃ and/or NaOH are involved in diluting Bi and V sources in the adopted approach. The as-synthesized peanut-like samples are rough and porous on the surface and to some extent are interior-hollow. The degradation of methylene blue (MB) is employed to evaluate the photocatalytic activity of the Bi ₂O ₃-BiVO ₄ composite. It is observed that the composite performs much better than Bi ₂O ₃ and BiVO ₄, plausibly due to heterojunctions formed between Bi ₂O ₃ and BiVO ₄. To investigate the relationship between structure and performance, the as-synthesized samples are characterized by XRD, XPS, SEM, TEM (HRTEM), UV-vis DRS, PL and nitrogen adsorption-desorption methods. Additionally, a possible growth mechanism of this hollow peanut-like structure and the separation process of photogenerated electron-hole pairs on the heterojunctions have been discussed.