MnO₂/TiO₂Nanotube Array-Coated Titanium Substrates as Anodes for Electrocatalytic Oxidation of As(III) in Aqueous Solution

The conversion of As(III) to As(V) in groundwater is an urgent issue, owing to the higher mobility, stronger toxicity, and weaker binding ability of As(III). In this work, the electrocatalytic oxidation of As(III) was efficiently achieved with a facile and environmentally benign method by using hierarchical MnO₂-deposited TiO₂nanotube arrays (MnO₂/TNAs) as the anode. The electrocatalytic oxidation performance of the as-fabricated MnO₂/TNA-coated anode was systematically investigated. The results exhibited that such as-fabricated MnO₂/TNAs had a high oxidation efficiency of 90% at a low concentration of As(III) (1 mg L^-1). Furthermore, the reaction mechanism was systematically studied by electron spin resonance and free radical capture experiments. The oxidation of As(III) was accomplished via both direct oxidation on the anode surface and indirect oxidation of the reactive oxygen species. The highly efficient TNA-based anode offers a potentially promising advanced material for electrochemical oxidation of trace As(III) in the practical field.