A nanocrystalline oxygen-deficient bismuth oxide as an efficient adsorbent for effective visible-light-driven...

In this work, a simple binary oxygen-deficient Bi₂O_4-x oxide was prepared, and its crystal structure, optical property, band structure and electronic structure were systematically investigated. Plane-wave-based density functional theory (DFT) calculations were also carried out to determine that Bi₂O_4-x is a typical indirect-gap semiconductor with the bandgap of 1.1 eV. Bi₂O_4-x adsorbed ca. 99% of rhodamine B and methyl orange, ca. 95% of methylene blue and ca. 80% of phenol in the dark within initial 30 min. The interaction of the oxygen-deficient structure-induced hydroxyls with pollutant molecules is responsible for the excellent adsorption capacity. Due to its excellent adsorption capacity, Bi₂O_4-x showed much higher photocatalytic degradation activity toward these pollutants (except for methylene blue) under visible light irradiation than the well-studied Bi₂O₄, Bi₂O₃ and P25, which had poor or negligible adsorption capacity toward the pollutants. Methylene blue was degraded by Bi₂O_4-x with further Pd loading. The photocatalytic mechanism of the oxygen-deficient Bi₂O_4-x were explored. The scavenging test results showed that direct h⁺ oxidation contributes to the high photocatalytic activity of the oxygen-deficient Bi₂O_4-x. This study highlights the potential of developing Bi₂O_4-x-based materials as a new class with both excellent adsorption capacity and highly efficient photocatalytic activity toward versatile pollutants.