Photoanodes made of metal oxides are considered to be a viable solution for the production of hydrogen with sunlight. Alpha-SnWO4 has optimal electronic properties for photoelectrochemical water splitting with sunlight, but corrodes easily. Protective layers of nickel oxide prevent corrosion, but reduce the photovoltage and limit the efficiency. Now a team has investigated at BESSY II what happens at the interface between the photoanode and the protective layer.