Photocatalytic oxidation of nitrogen oxides (NO x ) using Ag- and Pt-doped TiO 2 nanoparticles under visible light irradiation.

In this work, titanium dioxide nanoparticles (TiO ₂ NPs) and modified TiO ₂ NPs with silver (Ag) or platinum (Pt) dopant were developed through photodeposition method for the NO _x conversion into nitric acid (HNO ₃ ) under visible light irradiation. The formed photocatalysts TiO ₂ , Ag/TiO ₂ , and Pt/TiO ₂ nanocomposites were characterized by utilizing TEM, SEM, energy-dispersive X-ray analysis (EDX), XRD, UV/visible diffuse reflectance spectroscopy (UV-Vis DRS), and FT-IR. It had been investigated that an enhancement within the conversion of NO _x into HNO ₃ was increased from 34.3 to 78.3% for Ag/TiO ₂ and from 35.2 to 78.5% for Pt/TiO ₂ under visible light irradiation conditions at room temperature for less than 2 h. The photodegradation rate order of NO _x under visible light irradiation is Pt/TiO ₂ ~ Ag/TiO ₂ > TiO ₂ . A possible mechanism for the catalytic conversion of NO _x gases has been proposed, which depends on the photogeneration of electrons and holes after the excitation of nanocatalysts under visible radiation that promoted superoxide and hydroxyl ions, which can depredate NO _x gases. This approach of NO _x photocatalytic conversion is characterized by its chemical stability, low cost, high efficiency, simple operation, and strong durability than traditional methods.