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 O 2 nanobubbles generated by electrooxidation of hydrogen peroxide (H 2 O 2 ). A single bubble reproducibly nucleates when the dissolved O 2 concentration reaches ∼0.17 M at the Pt electrode surface. This nucleation concentration is ∼130 times higher than the equilibrium saturation concentration of O 2 and is independent of electrode size. Moreover, in acidic H 2 O 2 solutions (1 M HClO 4 ), in addition to producing an O 2 nanobubble through H 2 O 2 oxidation at positive potentials, individual H 2 nanobubbles can also be generated at negative potentials. Alternating generation of single O 2 and H 2 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.