Facile Hydrothermal Synthesis of Z-Scheme Bi2Fe4O9/Bi2WO6 Heterojunction Photocatalyst with Enhanced Visible Light Photocatalytic Activity

An efficient binary Bi₂Fe₄O₉/Bi₂WO₆ Z-scheme heterojunction was fabricated through a facile hydrothermal route. The obtained Bi₂Fe₄O₉/Bi₂WO₆ displays high catalytic activity for rhodamine B (RhB) photodegradation, and 100% of RhB was photodegraded by Bi₂Fe₄O₉ (7%)/Bi₂WO₆ within 90 min, which is much better than that by pure Bi₂Fe₄O₉ and Bi₂WO₆. The effective photoinduced carrier separation, the broadened photoabsorption range, high oxidation capacity of hole, and the high reduction power of electron are in charge of the elevated catalytic activity because of the formed Z-scheme system. In addition, the effects such as pollutant concentration, pH, inorganic anions, and water sources exerted on photocatalytic performance were also investigated, and the results suggest that Bi₂Fe₄O₉/Bi₂WO₆ still possesses a high photocatalytic performance. The free-radical trapping experiments and electron spin resonance spin-trapping technology disclose that hole (h⁺), hydroxy radical (^•OH), and superoxide radical (^•O₂^-) are cardinal active radicals in the catalytic system. In terms of the above experimental analysis, a possible photodegradation mechanism of the as-fabricated photocatalyst is thoroughly elucidated. In addition, the possible RhB photodegradation pathway is also raised in the light of the analysis of liquid chromatography-mass/mass spectrometry. In addition, Bi₂Fe₄O₉/Bi₂WO₆ composite does not display dramatic reduction of the catalytic performance after five recycles. Thus, this study reveals that the as-obtained Bi₂Fe₄O₉/Bi₂WO₆ catalyst has a great prospect for the environmental purification.