Enhanced photocatalytic removal of NOx gases by β-Fe2O3/CuO and β-Fe2O3/WO3 nanoheterostructures

The increasing release and accumulation of harmful nitrogen oxides (NOx with x = 1,2) in industrial and urban environments renders the efficient removal of these atmospheric pollutants an urgent and obligatory issue. In this regard, the advantages yielded by photocatalytic oxidation processes have triggered the search for eco-friendly catalysts featuring an improved efficiency. In this work, we propose the use of heterostructures based on beta-Fe2O3, a scarcely investigated iron(III) oxide polymorph, as viable De-NOx photocatalysts with appealing functional performances. The present materials were fabricated in supported form by chemical vapor deposition (CVD) of Fe2O3. A proof-of-principle investigation on the modulation of material performances by heterostructure formation is explored through Fe2O3 functionalization with CuO or WO3 by radio frequency (RF)-sputtering. The obtained results reveal a controllable dispersion of CuO or WO3 in close contact with beta-Fe2O3, a crucial issue to profitably exploit their mutual interplay for De-NOx applications. A preliminary analysis in this regard evidenced very encouraging conversion efficiency and selectivity towards nitrate formation, outstanding among non-titania oxide-based De-NOx photocatalysts. The improved photoactivity with respect to bare Fe2O3, CuO and WO3 was related to a higher oxygen defectivity and an enhanced separation of photogenerated charge carriers, enabled by the matched band edges in the target heterostructures.