Evaluation of surface phenomena involved in photocatalytic degradation of Acid Blue 9 by TiO2 catalysts of single and mixed phase - A theoretical and experimental study

The performance of two TiO2 catalysts, anatase powder (ALD) and Degussa P25 (DP25), was evaluated through photodegradation of Acid Blue 9 (AB9). The results were used to exhibit a sort of selectivity identified in these systems. The photodegradation was performed through a batch annular non-sleeve photoreactor. The kinetic constant values (k) and discolouration profiles exhibited a sort of catalytic selectivity. The results were explained by surface phenomena approach through experimental and theoretical means, employing UV-Vis, X-ray diffraction, Z potential, DFT-Koopman's descriptors and the catalyst total binding energy ((E-Bin,E-T)(i,j)). This contribution propose (E-Bin,E-T)(i,j) equation, which involves theoretical (binding energies (E-binding)) and experimental (relative intensity of the main crystalline catalyst planes) variables. The photocatalysis using ALD showed the highest k; but the photocatalysis with DP25 exhibited a linear discolouration profile, indicating a complete degradation of AB9 and their by-products. The k values agreed with (E-Bin,E-T)(i,j)). so the performance of TiO2 catalysts was attributed to Ebinding; these energies are product of the hydrogen bonding between the catalyst crystalline planes and AB9, in aqueous medium. Also, two different AB9 pathways were identified through DFT-Koopman's descriptors. The theoretical tools showed in this contribution are useful to understand the catalyst affinity and degradation pathways of pollutants.