Inhibit the formation of toxic methylphenolic by-products in photo-decomposition of formaldehyde–toluene/xylene mixtures by Pd cocatalyst on TiO2

Photocatalytic removal of single volatile organic compounds (VOCs) has been widely investigated; however, photodecomposition VOC mixtures rarely addressed, which may bring safety doubts in indoor air purification due to possible formation harmful compounds. Here we show that photocatalytic oxidation formaldehyde–toluene and formaldehyde–xylene mixtures, the introduction Pd cocatalyst on TiO2 photocatalyst successfully inhibits toxic methylphenols, thus promoting complete mineralization into CO2 via harmless benzaldehyde intermediates. Mechanistic analysis reveals loading effectively removes inherent surface −OH groups TiO2, significantly promotes activation O2 OH radicals. The also directs radicals attack methyl group instead aromatic ring for its further CO2, yielding a better overall performance.