Self-cleaning electrode for stable synthesis of alkaline-earth metal peroxides

Abstract

Alkaline-earth metal peroxides (MO₂, M = Ca, Sr, Ba) represent a category of versatile and clean solid oxidizers, while the synthesis process usually consumes excessive hydrogen peroxide (H₂O₂). Here we discover that H₂O₂ synthesized via two-electron electrochemical oxygen reduction (2e⁻ ORR) on the electrode surface can be efficiently and durably consumed to produce high-purity MO₂ in an alkaline environment. The crucial factor lies in the in-time detachment of in situ-generated MO₂ from the self-cleaning electrode, where the solid products spontaneously detach from the electrode to solve the block issue. The self-cleaning electrode is achieved by constructing micro-/nanostructure of a highly active catalyst with appropriate surface modification. In experiments, an unprecedented accumulated selectivity (~99%) and durability (>1,000 h, 50 mA cm⁻²) are achieved for electrochemical synthesis of MO₂. Moreover, the comparability of CaO₂ and H₂O₂ for tetracycline degradation with hydrodynamic cavitation is validated in terms of their close efficacies (degradation efficiency of 87.9% and 93.6% for H₂O₂ and CaO₂, respectively).