Evaluation of Photoelectrocatalysis with Electrode Based on Ti/RuO₂-TiO₂ Modified with Tin and Tantalum Oxides for the Degradation of Indigo Blue Dye

Indigo Blue (IB) is a dye widely used by the textile sector for dyeing cellulose cotton fibers and jeans, being considered a recalcitrant substance, and therefore resistant to traditional treatments. Several methodologies are reported in the literature for the removal or degradation of dyes from the aqueous medium, among which photoelectrocatalysis stands out, which presents promising results in the degradation of dyes when a dimensionally stable anode (DSA) is used as a photoanode. In the present work, we sought to investigate the efficiency of a Ti/RuO₂-TiO₂ DSA modified with tin and tantalum for the degradation of Indigo Blue dye by photoelectrocatalysis. For this, electrodes were prepared by the thermal decomposition method and then a physical-chemical and electrochemical analysis of the material was carried out. The composition Ti/RuO₂-TiO₂-SnO₂Ta₂O₅ (30:40:10:20) was compared to Ti/RuO₂-TiO₂ (30:70) in the photocatalysis, electrocatalysis, and photoelectrocatalysis tests. The photocatalysis was able to degrade only 63% of the IB at a concentration of 100 mg L^-1 in 3 h, whereas the electrocatalysis and photoelectrocatalysis were able to degrade 100% of the IB at the same initial concentration in 65 and 60 min, respectively.