Electrocatalytic activity of metal-doped SnO₂ for the decomposition of aqueous contaminants: Ta-SnO₂ vs. Sb-SnO₂

Sb-doped SnO₂ (ATO) is one of the most widely used electrocatalyst anodes for the oxidation of water and wastewater. This study synthesizes Ta(V)-doped SnO₂ (TTO) electrocatalysts as alternatives to ATO and systematically examines their electrocatalytic activity for the decomposition of organic substrates in various electrolyte solutions. The as-synthesized TTO exhibits the highest activity for the decomposition of phenol, N,N′-dimethyl-4-nitrosoaniline, and rhodamine-B at a Ta doping level of ~1%. The optimized TTO exhibits a higher activity for the decomposition of phenol than ATO in a chloride solution and a lower activity than ATO in a sulfate solution. Electron paramagnetic resonance analysis reveals that a relatively larger production of reactive oxygen species is achieved with ATO, whereas a larger production of reactive chlorine species is obtained with TTO. In the durability tests, both electrodes favor an alkaline condition (pH 12.8) over acidic and neutral conditions (pH 1.5 and 6.2, respectively), and Ta-SnO₂ is less stable than Sb-SnO₂ over the full pH range. Additionally, solid-state and electrochemical surface characterizations are carried out.