Effect of hydrophobicity on the hydrophobic-modified polytetrafluoroethylene/PbO2 electrode towards oxygen evolution

The effects of hydrophobicity toward oxygen evolution in 1 M H2SO4 on the PbO2 and polytetrafluoroethylene (PTFE)/PbO2 electrode were elucidated in this study via an analysis of d.c. polarization and the a.c. impedance response together with the technique of atomic force microscopy (AFM). A marked decrease in overvoltage for the oxygen evolution reaction was observed on the hydrophobic-modified PTFE/PbO2 anode when compared with a PbO2 anode. The smaller electrochemically active area was indicated by the smaller value of both the electrochemically active surface area (charge Q*) and the capacitance Cdl of the working electrode present on the hydrophobic PTFE/PbO2 than on the PbO2 electrode. Additionally, a smoother topology was also observed from the AFM to be present on the hydrophobic PTFE/PbO2 than on the PbO2 electrode. A higher relative rate for the oxygen evolution in 1 M H2SO4 on hydrophobic PTFE/PbO2 than on PbO2 was ascribed to both the bubble-removing effect caused by the hydrophobic centers and the fact that lower electrochemically active surface area for the anodic composite electrodeposition of PTFE/PbO2 is compensated by the higher electrocatalytic activity of active sites under a high applied overvoltage. The electrochemical stability of the hydrophobic PTFE/PbO2 anode was inferred to be substantially enhanced when compared with the unmodified PbO2 anode. PbO2 modified with the hydrophobic PTFE center via anodic composite electrodeposition resulted in a marked improvement in the electrocatalytic activity of the electrochemically active sites. An alteration of the surface structure of hydrophobic-modified PTFE/PbO2 was also inferred from the observation of AFM image to be exhibited when compared with PbO2.