Preparation of TiO2 Nanorods@Ni-Foam for Photocatalytic Decomposition of Acetaldehyde—In Situ FTIR Surface Investigation

TNR@Ni-foam structures were prepared by an alkaline hydrothermal method in an autoclave in a strongly alkaline medium (10 M NaOH) at 150 °C with further acid washing (0.1 M HNO3) and a second hydrothermal treatment in an autoclave at 180 °C. Two TiO2 samples were used for preparation: anatase and P25 of mixed anatase and rutile phases. After the first step of hydrothermal treatment, a layered titanate structure was obtained (Na2Ti3O7). Acid washing caused the substitution of Na+ by H+ and launched the formation of TNR. After the second hydrothermal treatment at 180 °C, for the optimal quantity of acid used for washing (10 mL per 0.75 g of TiO2), titania was crystallized to an anatase phase with small quantities of brookite and rutile. The structures obtained from P25 exhibited more brookite and rutile than those based on the anatase precursor. The morphology of TNR@Ni-foam structures was observed by SEM. The obtained composites were tested for acetaldehyde photodegradation (240 ppm in air) during the continuous flow of gas (5 mL/min) through the reactor coupled with FTIR. The most active samples were those obtained from P25, which had a crystalline structure of TiO2 and contained the lowest quantity of residue Na species.