Enhancement of the activity and stability of PbO₂ electrodes by modifying with polydimethylsiloxane

The β-PbO₂ of a Ti/Sn-SbO_x/PbO₂ electrode was modified with polydimethylsiloxane (PDMS) (Ti/Sn-SbO_x/PbO₂-PDMS) through a facile electrodeposition method. The results from scanning electron microscopy, energy-dispersive spectrometry and X-ray diffraction demonstrated that the PDMS was irreversibly adsorbed on the β-PbO₂ of Ti/Sn-SbO_x/PbO₂-PDMS, leading to a decrease in the crystal size, surface cracks and preferential growth trend of β-PbO₂. Compared with its PDMS-unmodified counterparts, the Ti/Sn-SbO_x/PbO₂-PDMS electrode exhibited relatively higher activity, selectivity and stability in the anodic oxidation of p-chlorophenol. Moreover, the Ti/Sn-SbO_x/PbO₂-PDMS electrode was more stable than the Ti/Sn-SbO_x/PbO₂ electrode, as evidenced by the accelerated life test. Based on the quantitative measurements of contact angle, hydroxyl radicals (HO•) and the initial surface concentration of various p-substituted phenols, including p-cresol, p-methoxyphenol, phenol, and p-chlorophenol, and with the help of electrochemical characterization of linear sweep voltammetry, it could be concluded that the improved electrochemical activity and stability of Ti/Sn-SbO_x/PbO₂-PDMS originated from the enhanced hydrophobicity of the electrode surface. Different from a traditional Ti/Sn-SbO_x/PbO₂ electrode with adsorbed HO• as the dominant active species, the Ti/Sn-SbO_x/PbO₂-PDMS with a hydrophobic surface favors the generation of more free HO•.