Enhancing visible light degradation of gaseous formaldehyde with CuO/OVs-TiO photocatalyst loaded wallpaper: Preparation, efficacy and mechanism.

Photocatalytic oxidation is considered to be a highly promising technology for indoor formaldehyde (HCHO) abatement. However, powdered photocatalysts encounter practical challenges due to their recycling difficulties and propensity for aggregation. In this study, we developed a CuO/OVs-TiO photocatalyst dispersion using various physical and chemical methods, which could be stabilized for an extended period. Subsequently, this catalyst was applied as a coating on nonwoven wallpaper (WP) to fabricate a novel CuO/OVs-TiO/WP composite which exhibited efficient photocatalytic performance in degrading gaseous HCHO under visible light irradiation. The physicochemical properties, photocatalytic activity and degradation mechanism of CuO/OVs-TiO/WP were systematically investigated through adsorption-photocatalytic degradation experiments, in-situ diffuse reflectance Fourier transform infrared spectroscopy (in-situ DRIFTS), and other analytical techniques. Results showed that the adsorption capacity of CuO/OVs-TiO/WP was 1.94 and 1.23 times higher than that of the individual photocatalyst or wallpaper, respectively. In addition, after 180 min of visible light irradiation, the HCHO removal rate achieved by CuO/OVs-TiO/WP reached 76.26%, representing a 52.54% enhancement compared to WP alone. Free radical quenching experiments and in-situ DRIFTS measurements were employed to elucidate the mechanism of photocatalytic oxidation of HCHO. It was found that hydroxyl radical (·OH) played a ruling role in HCHO decomposition, with HCHO initially oxidized to dioxymethylene (DOM), subsequently converted to formate species, and ultimately oxidized to carbonate or HO and CO. Furthermore, the degradation of HCHO by CuO/OVs-TiO/WP remained above 65% after five cycles, demonstrating a cycling stability of 86.88%. This study provides valuable insights for the photocatalytic treatment of indoor HCHO.