A nanocrystalline oxygen-deficient bismuth oxide as an efficient adsorbent for effective visible-light-driven photocatalytic performance toward organic pollutant degradation

In this work, a simple binary oxygen-deficient Bi2O4-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 Bi2O4-x is a typical indirect-gap semiconductor with the bandgap of 1.1 eV. Bi2O4-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, Bi2O4-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 Bi2O4-x with further Pd loading. The photocatalytic mechanism of the oxygen-deficient Bi2O4-x were explored. The scavenging test results showed that direct h. oxidation contributes to the high photocatalytic activity of the oxygen-deficient Bi2O4-x,. This study highlights the potential of developing Bi2O4-x-based materials as a new class with both excellent adsorption capacity and highly efficient photocatalytic activity toward versatile pollutants. (C) 2018 Elsevier Inc. All rights reserved.