Rules for selecting metal additives based on electron structure and HCHO oxidation efficiency between modified-TiO2(B) photocatalyst and metal cocatalyst Pd/Cu/Na

Abstract

Metal additives can greatly improve the catalytic oxidation of photocatalysts for degrading volatile organic compounds (VOCs) including formaldehyde. Different type metal, including Pd, Cu and Na, were doped in TiO2(B) nanosheets with oxygen vacancy, and the degradation rate of HCHO were evaluated using the above catalysts. A series of theoretical and experimental studies on these modified TiO2(B) photocatalysts were carried out. The presence of Ov leads to the appearance of impurity levels under the conduction band of TiO2(B), which could enhance the absorption in the visible spectral range by reducing the band gap and inhibiting the recombination of photo-induced charges. TiO2(B) with oxygen vacancies and doped with Na is used as a photocatalyst for degrading HCHO, and the removal rate up to 80% within 50 min. It is quite important to match the bandgap structure of photocatalysts and redox potential of O2/•O2−. Doping of excessive metals is detrimental to the separation and transfer of photogenerated charges. The intermediates and mechanism of photocatalytic oxidation of HCHO were investigated by in situ DRIFTS.