https://phys.org/news/2018-07-solar-hydrogen-efficient-microgravity.html

The researchers explain that the current process involves using an electrode made of a semiconductor that is light absorbing: Typically, a p-type indium phosphide. The electrode is then coated with a thin layer of a rhodium catalyst. As has been noted in the past, the inefficiency lies in the problem of hydrogen bubbles adhering to the surface of the electrodes, rather than bobbling up off them (due to buoyancy) as occurs on Earth. To get them to bobble up in a microgravity environment, the researchers changed the texture of the electrode. Rather than the normal flat surface, the team forced the rhodium into peaks and valleys, with the distance between them too far for the hydrogen bubbles to sit in. That meant they had to sit on the peaks, which left less contact between the bubbles and the surface.

To test their idea, the researchers created capsules containing their apparatus and dropped them 120 meters down the Bremen Drop Tower in Germany. They note that each drop occurred over approximately 9.3 seconds—enough time for their device to produce hydrogen gas.