Photocatalyst

A method comprising:

• placing a device including a photocatalyst adjacent a fluid stream, wherein
• the photocatalyst comprises a composite fiber,
• the composite fiber includes at least three n-type crystalline semiconductor materials,
• the n-type crystalline semiconductor materials form a heterojunction structure in the composite fiber, and
• the n-type crystalline semiconductor materials include bismuth oxide, titanium dioxide, and zinc oxide;
• and
• activating the photocatalyst, for photocatalytic reaction, with light incident on the photocatalyst for removing a contaminant from the fluid stream.

A device for removing a contaminant from a fluid stream, the device comprising a photocatalyst including a composite fiber, wherein

• the composite fiber includes at least two n-type crystalline semiconductor materials,
• the at least two n-type crystalline semiconductor materials form a heterojunction structure in the composite fiber,
• the at least two n-type crystalline semiconductor materials have band position alignments which allow vectorial displacement of electrons and holes,
• one of the at least two n-type semiconductor materials is bismuth oxide, and
• the composite fiber includes a p-type semiconductor material selected from the group consisting of copper (I) oxide, copper (II) oxide, cadmium telluride, and combinations thereof.

A method comprising:

• placing a device including a photocatalyst adjacent a fluid stream, wherein
• the photocatalyst includes a composite fiber,
• the composite fiber includes at least two n-type crystalline semiconductor materials,
• the at least two n-type crystalline semiconductor materials form a heterojunction structure in the composite fiber,
• the at least two n-type crystalline semiconductor materials have band position alignments which allow vectorial displacement of electrons and holes,
• one of the at least two n-type semiconductor materials is bismuth oxide, and
• the composite fiber includes a p-type semiconductor material selected from the group consisting of copper (I) oxide, copper (II) oxide, cadmium telluride, and combinations thereof;
• and
• activating the photocatalyst, for photocatalytic reaction, with light incident on the photocatalyst for removing a contaminant from the fluid stream.