Abstract: A photocatalyst element structure includes a photocatalyst element that includes a flat photocatalyst sheet and an undulating photocatalyst sheet overlapped on the flat photocatalyst sheet. The flat photocatalyst sheet and the undulating photocatalyst sheet include a porous titanium foil having a non-periodic spongy structure impregnated with anatase titanium dioxide particles. The photocatalyst element structure can include a plurality of the photocatalyst elements so that the flat photocatalyst sheet and the undulating photocatalyst sheet alternate.

Abstract: An air purification system includes an internally hollow cylindrical casing made of a non-conducting material; an inner electrode arranged on an inner surface of the supporting member; an outer electrode arranged on an outer surface of the supporting member; a photocatalyst filter arranged on an outer surface of the outer electrode for purifying air inside a plasma generation zone; and a power source for supplying power of opposite polarities to each of the inner electrode and the outer electrode so as to generate plasma. The photocatalyst filter includes a filter element, and the filter element includes a porous titanium foil having a non-periodic spongy structure impregnated with anatase titanium dioxide particles as a photocatalyst.