  A novel 3-electrode cell type is introduced to run parametrical studies of
H$_2$ evolution in an alkaline electrolyte on porous electrodes.
Electrochemical methods combined with a high-speed optical measurement system
are applied simultaneously to characterize the electrodes and the bubble
dynamics in terms of bubble size distribution and coverage of the working
electrode. Three different cathodes made of expanded nickel are investigated at
applied current densities of |j| = 10 to 200 mA cm$^{-2}$ without forced flow
and at a flow rate of 5 ml min$^{-1}$. The applied current density is found to
significantly influence both the size of detached bubbles and the surface
coverage of the working electrode. The forced flow through the cathodes is
found to strongly reduce the bubble size up to current densities of about 100
mA cm$^{-2}$, whereas the initial transient until the cathode surface is
completely covered by bubbles is only marginally affected by the flow-through.
