[en] GaN layers of n-type and p-type conductivity grown by HVPE on sapphire substrates were used as working electrodes for water electrolysis, photoelectrolysis and hydrogen gas generation. Specifically the water splitting process is discussed. Corrosion of the GaN materials is also considered. The hydrogen production rate under 365-nm UV LED irradiation of the GaN and external bias was 0.3 ml/(cm2*h) for an n-GaN photoanode (n∼8×10"1"6 cm"-"3) in 1M Na_2SO_4 electrolyte and 1.2 ml/(cm"2*h) for an n-GaN photoanode (n∼1×10"1"7 cm-3) in 1M KOH electrolyte. (paper)