Singlet-Oxygen Pathways in Electrocatalytic Ozone Evolution Promoted by Electrode/Electrolyte Synergy

Electrochemical ozone production (EOP) enables the direct generation of ozone (O3) from water oxidation to valorize anodic products, but its implementation is hampered by the competing oxygen evolution reaction (OER) and poor stabilization of oxygen species with insufficient mechanistic understanding. Herein, we report an electrode/electrolyte synergy strategy with the Ni/Mo-SnO2 catalyst and dihydrogen phosphate ion (H2PO4–) electrolyte for efficient EOP under open systems. This open-system EOP can deliver a continuous effluent of 2.5 ppm of O3 at a flow rate of 1 L/min with a much higher Faradaic efficiency than the standard PbO2 catalyst. Adsorbed singlet-oxygen (1O2) is identified as a key intermediate in the EOP mechanism. Mo sites in Ni/Mo-SnO2 strongly adsorb 1O2 on the surface, which further couples with the oxygen species on a nearby Ni site toward the O3 evolution. Meanwhile, H2PO4– anions enriched in the double layer suppress proton-coupled steps by shielding from other electrolyte species and increase the lifetime of adsorbed 1O2 species toward efficient coupling. Finally, by leveraging the synergistic effects toward 1O2 stabilization, the system enables in situ O3-driven continuous oxidative degradation of alkenes with high conversions. This work established the 1O2-mediated EOP pathway, providing mechanistic insight into an open system/continuously operating the O3 evolution system.