Salt-assisted Synthesis of Hollow Bi₂WO₆Microspheres with Superior Photocatalytic Activity for NO Removal

Hollow Bi2WO6microspheres are successfully synthesized by a facile ultrasonic spray pyrolysis (USP) method using NaCl as a salt template. The as-prepared hollow microspheres assembled as nanoplates with dimensions of approximately 41-148 nm and are dispersed with non-uniform pores on the template surface. By swapping the salt template with KCl or Na2SO4, different morphologies of Bi2WO6are obtained. The experimental results demonstrate that NaCl plays a key role on the formation of Bi2WO6with hollow structures. The specific growth mechanism of hollow microspheres was studied in detail. The Bi2WO6hollow microspheres exhibit an excellent photocatalytic efficiency for NO removal under solar light irradiation, which is 1.73 times higher than for the Bi2WO6obtained in the absence of any salt template. This enhancement can be ascribed to the simultaneous improvement on the surface area and visible light-harvesting ability from the hollow structures. Electron spin resonance (ESR) results suggest that both radicals of •OH and •O2-are involved in the photocatalytic process over the BWO-NaCl sample. The production of •O2-radicals offers better durability for NO removal.