An anode active material-semiconductor hybrid electrode was prepared by combining electroplated Co and a GaP single crystal. This hybrid electrode acts not only as an active material for a cobalt-air cell but also as a photo-electrode for storing light energy. We studied the photoelectrochemical properties of the hybrid electrode, and confirmed that the electrode's oxidized Co layer was reduced by the electrons generated when the GaP side was illuminated. We assembled a GaP-ColKOHlO(2) cell with only two electrodes: the above hybrid electrode and an air electrode (oxygen catalyst). The photo-electrochemical characteristics of the Co-GaP hybrid electrode and cobalt-air cell showed that this cell can be charged by illuminating it and discharged by using the oxygen in the air. (C)., 2001 Elsevier Science B.V. All rights reserved.