A porous film semiconductor photoemitter with visible light response formed by a porous structure complex metal oxide semiconductor is used in photoelectric chemical cell reacted in the energy storage. The said photoemitter is composed of more than two kinds of elements: an is one of Bi, Ag, Cu, Sn, Pb, V, In, Pr Cr and Ni, B is selected from Ti, Nb, Ta, Zr, Hf, Mo, W, Zn, Ga, In, Ge and Sn. This invented simple device alters the visible light such as the sunlight to hydrogen chemical energy effectively, even if the photoemitter has very low quantum absorptivity yet it will approach to 100% so long as the filming method is perfect.