Improved photocatalytic Bi₂WO₆/BiOCl heterojunctions : one-step synthesis via an ionic-liquid assisted ultrasonic method and first-principles calculations

Abstract

<div lang="en" class="abs"><p class="abs_header">Abstract</p><p>Bi₂WO₆/BiOCl heterojunctions with high photocatalytic activity and photocurrent property were synthesized via an ionic-liquid assisted ultrasonic irradiation at room temperature. The ionic liquid 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) was used as the Cl source. Modifications of heterojunction structures and properties were realized just by changing the amount of [BMIM]Cl. Photocatalytic activities of Bi₂WO₆/BiOCl heterojunctions enable fast degradations of 2,4-dinitrophenol solution (DNP), rhodamine B (RhB) and quinoline blue (QB) under visible light and sunlight irradiation. Through first-principles calculations, the Bi-O bonding was found as junction structures at the interface, leading to band intercalations between the two parts besides the interface. Efficient charge (hole) transfers to two sides of the tungstate and chloride were enabled through interface during photocatalytic processes, resulting in longer electron-hole separations, and enhanced catalytic activities under sunlight radiation. The mechanism is crosschecked with transient photocurrent results where the BiOCl-Bi₂WO₆ heterojunction possess higher photocurrent than pure Bi₂WO₆ or BiOCl, ascribed to inhibition of electron-hole recombination in the photo processes.</p></div>