No abstract

Because of its metal-like conductivity, excellent catalytic activity, and acid resistance, lead dioxide (PbO2) is the most used electrocatalyst for the practical electrochemical ozone production (EOP) technique. Introducing fluorine (F) into PbO2 electrodes or electrolytes can significantly improve EOP activity. However, there is still lack of valid evidence on understanding the role of doping F in the PbO2 electrode. In this work, we report a comprehensive study on the effect of F on EOP activity on electrochemically prepared PbO2 electrodes. F doping suppresses the side reaction of dioxygen (O2) evolution by inhibiting the formation of an α phase impurity of PbO2 electrodes. The more hydrophobic surfaces by doping F promote O2 adsorption as evidenced by low-temperature O2-temperature-programmed desorption experiments and thus are more favorable for ozone (O3) generation. The in situ isotope labeling oxygen (18O2) experiment proves that at room temperature, O2 can adsorb and dissociate on the operando PbO2 electrode surface and participate in the formation of O3 molecules. This work provides a comprehensive understanding of doping F for enhanced EOP.

Traditional electrochemically prepared lead dioxide (e-PbO 2 ) is one of the most used electrode materials for electrochemical ozone production (EOP), because of its high catalytic activity, excellent electrical conductivity, relative stability and low cost. But the electrochemically prepared conditions are complicated and harsh. Bulk PbO 2 electrodes have the very limited surface area and are inconvenient to process into the fine film electrodes for a PEM electrolyser. In contrast, chemical synthesis is easy to prepare uniform PbO 2 catalysts with high surface area and catalytic activity. Here, a facile one-pot approach to prepare a highly active PbO 2 microsphere catalyst was established and used for the EOP reaction in a PEM ozone generator. Sodium hydroxide could be used to regulate the relative content of α/β allotropic phase and crystallite size of PbO 2 microspheres. Experiment results revealed that high β phase content and large β-PbO 2 crystallite size were beneficial to the high EOP activity. By optimizing the composition and crystal structure, chemically prepared PbO 2 could have much better EOP performance than e-PbO 2 .[a] Q.