Detachment characteristics of hydrogen bubbles in water electrolysis

Hydrogen production from renewable energy through water electrolysis is a key technology for the energy transition. One present bottleneck is a lack of understanding of the dynamics of the electrolytic bubbles near the electrode surfaces as their presence can significantly impact electrolyzer efficiency, e.g. by blocking active sites. In this work, we experimentally investigate the detachment characteristics of the hydrogen bubbles formed in water electrolysis on a Pt electrode. We observe that for acid concentrations of 0.1 M and beyond, contact line spreading plays a dominant role in bubble behaviour. The buoyancy driven departure of the spreading bubble is not well described by the widely used Fritz model, which assumes a static contact angle. Instead, our data shows that the initial spreading is followed by contact line pinning, which can be understood when accounting for dynamic wetting effects. In addition to buoyancy driven bubble detachment, we also observe coalescence-triggered bubble departure and analyse the contact line dynamics for this case. Our results suggest that the radius ratio is an important, but not the only parameter determining the detachment of coalescing bubbles.