Structure and Photocatalytic Properties of Ni-, Co-, Cu-, and Fe-Doped TiO2 Aerogels

TiO2 aerogels doped with Ni, Co, Cu, and Fe were prepared, and their structure and photocatalytic activity during the decomposition of a model pollutant, acid orange (AO7), were studied. After calcination at 500 °C and 900 °C, the structure and composition of the doped aerogels were evaluated and analyzed. XRD analysis revealed the presence of anatase/brookite and rutile phases in the aerogels along with other oxide phases from the dopants. SEM and TEM microscopy showed the nanostructure of the aerogels, and BET analysis showed their mesoporosity and high specific surface area of 130 to 160 m2·g−1. SEM–EDS, STEM–EDS, XPS, EPR methods and FTIR analysis evaluated the presence of dopants and their chemical state. The concentration of doped metals in aerogels varied from 1 to 5 wt.%. The photocatalytic activity was evaluated using UV spectrophotometry and photodegradation of the AO7 pollutant. Ni–TiO2 and Cu–TiO2 aerogels calcined at 500 °C showed higher photoactivity coefficients (kaap) than aerogels calcined at 900 °C, which were ten times less active due to the transformation of anatase and brookite to the rutile phase and the loss of textural properties of the aerogels.