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

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.