The effect of wetting properties on bubble dynamics and fuel distribution in the flow field of direct methanol fuel cells

► We investigate CO2 bubble dynamics by visualisation (side view) in a DMFC anode. ► We vary channel wettability and consider diffusion layer intrusion. ► We study the correlation between bubble and channel velocity experimentally. ► We specify a setup where bubble bypasses can only develop along the diffusion layer. ► We model average bubble bypass flow velocity quantitatively.