Reductive energy generated by using photocatalysts under UV light can be stored in coupled energy storage materials, and the stored energy can be used in dark. TiO₂ and SrTiO₃ are used as photocatalysts and WO₃ and MoO₃ as energy storage materials. The energy storage is possible not only in electrolytes but also in non-electrolytic media including pure water and humid air. The mechanism of the energy storage by photocatalysts and charge-discharge behavior are discussed as well as their applications. Energy storage photocatalysts retain their anti-corrosion effect and anti-bacterial effect even after the UV light is turned off.