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

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 TiO 2 (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 TiO 2 (B) photocatalysts were carried out. The presence of O v leads to the appearance of impurity levels under the conduction band of TiO 2 (B), which could enhance the absorption in the visible spectral range by reducing the band gap and inhibiting the recombination of photo-induced charges. TiO 2 (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 O 2 /•O 2 − . 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.