Understanding the energy level matching relationships between semiconductor photocatalysts and organic pollutants for effective photocatalytic degradations.

In this work, representative semiconductors CdS, VO, WO and P25 (Degussa TiO consisting of 80 wt% anatase and 20 wt% rutile) were chosen as the photocatalysts, and the common phenol along with its derivatives (p-nitrophenol, p-chlorophenol and hydroquinone) were designated as the probe pollutants. The energy levels of the frontier molecular orbitals (E and E) of organics, and the valence band (VB) and conduction band (CB) energy levels (E and E) of photocatalysts were obtained through experiments and calculations. By correlating the photocatalytic activities of photocatalysts for the degradations of the organic pollutants under the irradiation of a 300 W xenon lamp with their above-mentioned energy levels, some new findings can be acquired. To be specific, the more positive E of an organic pollutant leads to its easier photodegradation by photocatalysts. Meanwhile, the more negative VB position for a photocatalyst results in the higher photocatalytic activities for the degradations of organic pollutants. Therefore, the matching correlation between the E of an organic pollutant and the E of a photocatalyst is of great importance to the efficiency of photocatalytic degradation.