Highly selective electrochemical synthesis of ClO2 from chlorite with Ti4O7 for rapid pollutants degradation and safe disinfection

Abstract

Industrial synthesis of chlorine dioxide (ClO₂) is infrastructure-demanding and presents significant safety and transportation challenges. The electrochemical method, while offering an on-site ClO₂ production alternative, suffers from risky chlorate (ClO₃⁻) generation, even when using a widely-utilized noble metal-based dimensionally stable anode (DSA). In this study, we report that a Ti₄O₇ anode can efficiently convert chlorite (ClO₂⁻, 25 mmol L⁻¹) to ClO₂ with an impressive selectivity of 99% at 10 mA cm⁻². Unlike DSA, which generates abundant free hydroxyl radicals (•OH) that over-oxidize ClO₂⁻ into ClO₃⁻ via a 2:1 stoichiometry, the Ti₄O₇ anode confines •OH onto its surface, facilitating selective ClO₂⁻ oxidation through single-electron transfer reaction. With this novel Ti₄O₇ anode, a portable ClO₂ gas generator was designed to continuously deliver high-purity and cost-effective ClO₂ at a rate of 3.30 g h⁻¹ with high stability over 5-day operational period, and thus is very promising for rapid water pollutants (sulfamethazine, ciprofloxacin, cephalexin, tetracycline, and carbamazepine) degradation and safe disinfection against pathogens (E. coli, S. aureus, and AR E. coli) in minutes with minimal chlorinated byproducts.