Durability of Ag‐TiO2 Photocatalysts Assessed for the Degradation of Dichloroacetic Acid

The stability of Ag‐TiO2 photocatalysts was examined for the photocatalytic degradation of dichloroacetic acid (DCA) as a function of the recycling times. The photocatalytic activity was investigated by measuring the rate of H+ ions released during the photodegradation of DCA and confirmed by measuring the total organic carbon removal. The photodegradation reactions were studied at pH 3 and pH 10 for a series of Ag‐TiO2 photocatalysts as different with Ag loadings . All the Ag‐TiO2 and bare TiO2 photocatalysts showed a decrease in photocatalytic activity on recycling for the DCA photodegradation reaction. The decrease in activity can be attributed to poisoning of active sites by Cl− anions formed during the photocatalytic DCA degradation. The photocatalytic activity was, however, easily recovered by a simple washing technique. The reversibility of the poisoning is taken as evidence to support the idea that the recycling of Ag‐P25 TiO2 photocatalysts does not have a permanent negative effect on their photocatalytic performance for the degradation of DCA. The choice of the preparation procedure for the Ag‐TiO2 photocatalysts is shown to be of significant importance for the observed changes in the photocatalytic activity of the Ag‐TiO2 particles.