Preparation of porous oxide layers by oxygen bubble templated anodic deposition followed by galvanic displacement

- Porous PbO2 reacts with Mn2+, Co2+ or Sn2+ to form layers of MnO2, Co3O4 and SnO2.
- Galvanic displacement between PbO2 and cations in solutions occurs at open circuit.
- MnO2, Co3O4 and SnO2 deposit on top of porous PbO2.
- Co3O4-modified porous PbO2 electrodes are active in the oxygen evolution reaction.

Galvanic displacement reactions between porous PbO2, prepared by oxygen bubble templated anodic deposition, and the low-valent cations Mn2+, Co2+ and Sn2+, have been studied using electrochemical methods, SEM-EDS and XPS. These reactions occur at open circuit by immersion of PbO2 coated electrodes in aqueous solutions of the cations and lead to the formation of outer oxide layers onto porous PbO2, whose composition and chemical nature have been assessed by XPS. The growth of the outer oxide layers has been studied by combining Evans' diagrams with SEM-EDS and XPS results, as a function of experimental variables, such as the chemical nature of the cations, their concentration and the solution temperature. The combination of oxygen bubble templated anodic deposition and galvanic displacement provides a route for the preparation of porous low-conductivity electroactive oxides not attainable by direct electrodeposition. Deposition of Co3O4 thin layers by galvanic displacement results in a strong enhancement of the activity of porous PbO2 electrodes in the oxygen evolution reaction.

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