Electrochemical Generation of Individual O Nanobubbles via HO Oxidation.

Herein, we use Pt nanodisk electrodes (apparent radii from 4 to 80 nm) to investigate the nucleation of individual O nanobubbles generated by electrooxidation of hydrogen peroxide (HO). A single bubble reproducibly nucleates when the dissolved O concentration reaches ∼0.17 M at the Pt electrode surface. This nucleation concentration is ∼130 times higher than the equilibrium saturation concentration of O and is independent of electrode size. Moreover, in acidic HO solutions (1 M HClO), in addition to producing an O nanobubble through HO oxidation at positive potentials, individual H nanobubbles can also be generated at negative potentials. Alternating generation of single O and H 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.