Chemical etching fabrication of uniform mesoporous Bi@Bi2O3 nanospheres with enhanced visible light-induced photocatalytic oxidation performance for NOx

Abstract Bulk materials with a microporous structure are adverse to light adsorption, photoelectron and reactant transport in a photocatalytic reaction. Mesoporous photocatalysts have shown many marked advantages in photocatalytic fields. Herein, uniform mesoporous Bi@Bi2O3 nanospheres were fabricated by HCl–ethanol chemical etching at low temperature (60 °C). The obtained mesoporous photocatalysis increased the NO removal efficiency (16%) and inhibited toxic NO2 generation (3%) under visible light irradiation. Further oxidation of Bi and calcination at high temperatures were avoided during template removal. Moreover, the as-prepared sample possessed a remarkably narrower pore size distribution (3.2–3.9 nm) and stronger light and NO adsorption ability than the bulk microporous Bi@Bi2O3. Work function and the electron spin resonance test results also indicated that the position of the entire energy bands on Bi2O3 was lowered. The amount of reactive oxygen species generated over the uniform mesoporous structure was higher than that over bulk Bi@Bi2O3. However, photoelectrochemical measurements indicated that the separation efficiencies of the photo-generated carriers were not improved over the uniform mesoporous Bi@Bi2O3. Comprehensive studies have shown that the oxidation ability rather than the enhanced separation efficiency of charge carriers accounted for the enhanced photocatalytic activity. This work elucidates the roles of a uniform mesoporous structure in NOx photocatalytic oxidation and provides an efficient strategy for structural engineering in preparing highly reactive and practical photocatalysts.