Sodium Titanate Synthesis For The Photocatalytic Degradation of NO

Abstract

\n The synthesis and characterization of sodium titanates (ST) and its evaluation in the photocatalytic reduction of nitric oxide (NO) is described in this contribution. The materials were synthesized by an hydrothermal route using the following parameters; 5 M NaOH concentration used as TiO2 mineralizer agent, under 170 °C for 48 hours, and a dose of TiO2 of 0.06 mg/mL (expressed as the mass ratio of TiO2/mL with respect to NaOH); resulting in tri- and hexa- ST. A nanotubular morphology was observed for the ST as proved by scanning electron microscopy (SEM) and a subsequent heat-treatment at 400 °C allowed a complete transformation of tri- to hexa- sodium titanates to modify the bandgap. The obtained ST were impregnated with Ag+ and Zn+ cations, respectively (ST-Ag, ST-Zn), to tune the bandgap of the materials. XPS analysis of the ST-Ag materials showed evidence of metallic Ag pointing to the formation of silver nanoparticles, whereas for ST-Zn oxide phases were mainly spotted. The materials were evaluated for the photocatalytic reduction of NO using a reactor fed with a continuous flow rate of NO, generated in situ, at a flow rate of 280 ml/min using nitrogen and a 253 nm wavelength UV irradiation source. The photocatalytic tests showed that pristine ST (tri and hexa-titanate) was the photocatalyst that displayed the best performance in the reduction of NO with respect to the impregnated samples (ST-Ag, ST-Zn). Maximum efficiencies of 80% degradation were reached when using 1 g of photocatalyst with a flow of 280 ml/min and a lamp of 253 nm.