Synergistic promotion by highly active square-shaped lead oxide and visualized electrolyzer for enhanced electrochemical ozone production

Abstract

Electrochemical ozone production (EOP) is an intrinsically safe technology compared to Corona discharge methods for ozone generation. However, EOP technology exhibits higher electrical utility demand. Herein, a square-shaped lead oxide (PbOx-CTAB-120) electrocatalyst with outstanding EOP activity has been successfully prepared by a simple method. Then the PbOx-CTAB-120 was assembled into a newly visualized EOP electrolyzer (with parallel flow field) at 1.0 A cm−2 in ultrapure water. The gaseous ozone yield reached 588 mg h−1 g−1catalyst, corresponding to a specific energy consumption (PEOP) of 56 Wh g−1gaseous ozone. In-situ18O isotope-labelled differential electrochemical mass spectrometry reveals that PbOx-CTAB-120 undergoes phase shuttling to β-PbO2via the lattice oxygen oxidation mechanism pathway. Furthermore, density functional theory calculations for multiple reaction pathways on the Pb3O4 (110) surface also demonstrated the participance of lattice oxygen in the EOP process, with the results show that the oxygen vacancy generated from lattice oxygen migration could effectively stabilize the OOH* and O2* reaction intermediate in contrast to the adsorbate evolution mechanism. Therefore, the presence of highly stabilized surfaces Pb3O4 (110) on PbOx-CTAB-120 before phase shuttling and the stabilization of β-PbO2 (101) and β-PbO2 (110) crystalline surfaces after phase shuttling allowed PbOx-CTAB-120 to maintain its excellent EOP activity and stability. Moreover, based on computational fluid dynamics simulations and experimental observations, the parallel flow field design facilitated efficient mass transfer of the gaseous product (O2+O3) and effective thermal dissipation of the system. In addition, the high activity electrocatalyst coupled with the optimized EOP electrolyzer enabled efficient in-situ degradation of organic species.