Tuning the Selectivity: Evaluating Pt-Co and Pt-Ni Anchored on TiO2 for the Generation of Benign End Products in Photocatalytic Nitrate Reduction

This study addresses the urgent issue of nitrate-contaminated water by investigating Ni-Pt and Co-Pt catalysts supported on TiO2, with the aim of improving both photocatalytic efficiency and reaction selectivity. The influence of adding non-noble metal co-catalysts to TiO2, in addition to Pt, was explored. The synthesized samples were characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), hydrogen temperature-programmed reduction (H2-TPR), diffuse reflectance UV–Vis spectroscopy, photoluminescence (PL), and X-ray photoelectron spectroscopy (XPS). The assessment of catalytic performance was conducted during the catalytic hydrogenation of nitrate, followed by an evaluation of the photocatalytic performance achieved when the aqueous nitrate solution was irradiated with UV light. The focus is on assessing the synergistic effects of the catalysts supported on TiO2 in nitrate reduction, as well as their selectivity towards benign reaction products during the photocatalytic process, in contrast to the reactions occurring in the absence of light. Despite the selectivity for nitrite being preserved, the photocatalytic experiments indicated that the selectivity for N2 reached around 68%, which is about 1.5 times higher than the values observed during the dark catalytic reaction. In contrast, the selectivity for ammonium saw a notable reduction. The findings were discussed in relation to the characteristics of the synthesized materials.