Achieving maximum photo-oxidation reactivity of Cs_0.68Ti_1.83O_4−xN_x photocatalysts through valence band fine-tuning

Does a wider absorption range of the photocatalyst always result in a higher photoreactivity? By investigating a set of Cs_0.68Ti_1.83O_4−xN_x (x = 0–0.31) photocatalysts with a continuously tuned absorption edge, we found that although the absorption edge of Cs_0.68Ti_1.83O_4−xN_x is gradually shifted to the low-energy region with the increase of the nitrogen dopant, the photoreactivity of the photocatalyst in terms of generating the ˙OH radical does not correspondingly increase under the irradiation of monochromatic light of 254 nm and continuous spectrum of >300 nm. The fundamental mechanism of the anion dopant enhanced photocatalytic activity through the interplay of three key factors—absorbance, oxidative potential and mobility of charge carriers—is proposed to explain the observed photocatalytic activity change.