Phase shuttling-enhanced electrochemical ozone production

Ozone can be produced by the electrochemical oxidation of water, which provides a technical solution to on-demand ozone production for disinfection and sterilization. Lead oxides have been found to be unique in catalyzing such a process. However, the fundamental understanding of these catalysts’ mechanisms remains limited, hindering the development of high-performance catalysts for electrochemical ozone production (EOP). Herein, the effect of phase shuttling on the reactivity of Pb₃O₄ was systematically investigated during the EOP process by in situ/ex situ characterizations. It was found that Pb₃O₄ undergoes a phase shuttle towards b-PbO₂ via the lattice oxygen oxidation mechanism (LOM) pathway, and the reconstructed b-PbO₂ shows enhanced EOP activity and stability compared to commercial b-PbO₂. The ex situ characterization of materials combined with theoretical calculations reveals that the performance enhancement is mainly attributed to the stable presence of (101) and (110) surfaces in the reconstructed b-PbO₂ with undercoordinated Pb–O. Pourbaix diagrams of lead oxides calculated by DFT demonstrate that the phase shuttling to b-PbO₂ is thermodynamically favorable under EOP conditions. Surface Pourbaix diagrams of b-PbO₂(101) and Pb₃O₄(110) further reveal the adsorption behavior of O*/OH* intermediates and explain the observed change of EOP kinetics at B1.6 V vs. RHE. The catalyst is integrated and assembled in a membrane electrode assembly (MEA) electrolyzer, and the produced ozonated water successfully inactivated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This work provides a new insight into EOP catalysts and demonstrates the possibilities of further optimization of electrochemical approaches for on-demand ozone generation.