Facile construction of novel Z-scheme Bi4O5I2/CuFe2O4 heterojunctions for NO2-inhibited and robust photocatalytic removal of NO under visible light

Photocatalytic oxidation has been confirmed as a promising manner to control and treat low-concentration NO, during which the generation of hazardous intermediate NO2 is unavoidable, causing more severe health concerns and environmental pollution issues than NO itself. In this research, the photocatalytic removal of NO was studied over novel Bi4O5I2/CuFe2O4 (BCF) binary composites that were constructed by a straightforward solvothermal route. CuFe2O4 nanoparticles and Bi4O5I2 nanosheets were coexisted in composites and merged into heterojunction structures with compatible morphologies. Under visible light, these resultant composites exhibited reinforced photocatalytic NO removal efficiency in comparison to bare components. Specifically, the best sample BCF3, defined as the composite with the mass percent of CuFe2O4 to Bi4O5I2 as 3%, presented the toxic intermediate NO2 as 21 ppb (part per billion) and the largest photocatalytic NO removal of 44% that referred to the ratio of removal to initial concentration of NO. NO removal and NO2 generation of BCF3 improved 1.5 times and reduced by half in only 5 min compared to that of pristine Bi4O5I2, which could be attributed to the strengthened visible light harvesting, efficient transfer and separation of charge carriers through intimate interfaces, and the availability of sufficient reactive radicals. Through entrapping experiments and band structure estimation, a Z scheme model was put forward for the photocatalysis mechanism of these robust n-p heterojunction composites.