Electrochemical Generation of Individual O₂ Nanobubbles via H₂O₂ Oxidation

Herein, we use Pt nanodisk electrodes (apparent radii from 4 to 80 nm) to investigate the nucleation of individual O₂ nanobubbles generated by electrooxidation of hydrogen peroxide (H₂O₂). A single bubble reproducibly nucleates when the dissolved O₂ concentration reaches ∼0.17 M at the Pt electrode surface. This nucleation concentration is ∼130 times higher than the equilibrium saturation concentration of O₂ and is independent of electrode size. Moreover, in acidic H₂O₂ solutions (1 M HClO₄), in addition to producing an O₂ nanobubble through H₂O₂ oxidation at positive potentials, individual H₂ nanobubbles can also be generated at negative potentials. Alternating generation of single O₂ and H₂ bubbles within the same experiment allows direct comparison of the critical concentrations for nucleation of each nanobubble without knowing the precise size/geometry of the electrode or the exact viscosity/temperature of the solution.