Direct Z-Scheme Cs₂O-Bi₂O₃-ZnO Heterostructures as Efficient Sunlight-Driven Photocatalysts

Limited light absorption, inefficient electron-hole separation, and unsuitable positions of conduction band bottom and/or valence band top are three major critical issues associated with high-efficiency photocatalytic water treatment. An attempt has been carried out here to address these issues through the synthesis of direct Z-scheme Cs₂O-Bi₂O₃-ZnO heterostructures via a facile, fast, and economic method: solution combustions synthesis. The photocatalytic performances are examined by the 4-chlorophenol degradation test under simulated sunlight irradiation. UV-vis diffuse reflectance spectroscopy analysis, electrochemical impedance test, and the observed transient photocurrent responses prove not only the significant role of Cs₂O in extending light absorption to visible and near-infrared regions but also its involvement in charge carrier separation. Radical-trapping experiments verify the direct Z-scheme approach followed by the charge carriers in heterostructured Cs₂O-Bi₂O₃-ZnO photocatalysts. The Z-scheme charge carrier pathway induced by the presence of Cs₂O has emerged as the reason behind the efficient charge carrier separation and high photocatalytic activity.