Wed October 25th 2017
16:00 – 17:00
ZH286
Seminar The nucleation rate of single O2 nanobubbles at conditioned nanoelectrodes
Álvaro Moreno Soto

Details:

Nanobubble nucleation is a problem that affects efficiency in electrolytic/catalytic reactions, since those bubbles can block the surface of the electrodes/reacting catalysts and prevent the reaction to continue or highly reduce its efficiency. In this presentation, we focus on the nucleation rate of O2 nanobubbles by electro-oxidation of H2O2. By applying different currents below the peak current, ipnb, at which nanobubbles are formed, we can measure different times required for nanobubble nucleation. The O2 nanobubble then blocks the surface of the reacting electrode on which the reaction occurs. We study in detail the different conditions in which a nanobubble appears and how they affect the electrode surface, concluding that for achieving reproducible results, the electrode surface needs to be pre-conditioned. Nucleation rate experiments show a similar trend to other nucleation experiments for other gases, such as H2: bubble nucleation is a stochastic process in which nucleation time, tind, drastically decreases as the applied current is closer to ipnb. Finally, we calculate the activation energy Ea, which varies in the range from 6 to 30 kT, and the geometry of the nanobubble nucleus regarding its contact angle to the electrode surface (achieving results in the interval from 135˚ to 155˚) and the number of O2 molecules contained in such a nucleus (which fluctuates from 50 to 900 molecules).
Go back to the agenda.

Rayleigh Benard convection conference 2018 rbc2018
Max Planck Gesellschaft
MCEC
Twente
Centre for Scientific Computing
Facebook
YouTube