Objective 3

Objective 3 — Contribution to the understanding of PEM electrolysers under two-phase flow conditions (May 2019 to May 2020):   In their work, Dedigama et al.[1] visualised the mechanism of oxygen bubble formation using a spectroscopy technique. They were able to observe:

• A single-phase regime occurring at low current densities (before the water-splitting reaction takes place), characterised by a laminar Reynolds number and a uniform presence of water in the channels.
• A two-phase regime in which the water-splitting reaction produces a mixture of oxygen bubbles and water in the channel.

In particular, the experimental campaigns carried out in London with Prof. Dan Brett during Dr Aubras’ PhD highlighted that slug-flow regimes affect the electrochemical performance of the cell. This issue is all the more important given that the next stationary applications of low-pressure electrolyser cells are moving towards operating points at which obstruction regimes appear (very high current densities). The literature review revealed that this phenomenon has received very little attention. One of the main objectives will therefore be to study the electrochemical behaviour (in collaboration with UCL London) of a PEM electrolyser cell during the onset of the slug-flow regime, by means of electrochemical impedance spectroscopy (EIS) and analytical modelling. Deliverables:

• Journal article: Aubras, F., Rhandi, M., Deseure, J., Kadjo, A. J. J., Bessafi, M., Majasan, J., … & Chabriat, J. P. (2021). Dimensionless approach of a polymer electrolyte membrane water electrolysis: Advanced analytical modelling. Journal of Power Sources, 481, 228858.
• International conference: Rhandi, M., Aubras, F., Kadjo, A. J. J., Druart, F., Grondin-Perez, B., & Deseure, J. (2019, September). Dimensionless approach of a pressurized proton exchange membrane water electrolysis. In 12th European Congress of Chemical Engineering, ECCE12 (pp. pp-1903).

[1] Dedigama, I., Angeli, P., van Dijk, N., Millichamp, J., Tsaoulidis, D., Shearing, P. R., & Brett, D. J. (2014). Current density mapping and optical flow visualisation of a polymer electrolyte membrane water electrolyser. Journal of Power Sources, 265, 97-103.