The simultaneous H-2 and O-2 evolutions can be achieved by just stirring a powder of a p-type semiconductor, such as Cu2O, NiO, Co3O4 or Fe3O4 in distilled water at room temperature. Frictional rubbing of the stirring rod onto the bottom of the glass vessel is an important condition. The friction between the stirring rod and the glass surface generates an electrostatic field to make a field emission of positive holes from the semiconductor-powder. which is fixed in the micro crack spaces on the glass surface. The emitted positive holes react with water molecules to evolve O-2 and protons, which go to the glass surface and combine with the electrons there to evolve H-2. The energy conversion mechanism, the generation of frictional electricity, the effect of the water, the carrier-tunnelling emission probability, the hopping conduction in the semiconductor, and the effects of fluid dynamics, are discussed.