An amorphous titanium peroxide sol made by a process which includes adding an alkali hydroxide to an aqueous titanium salt solution and reacting the resulting amorphous titanium hydroxide with an aqueous hydrogen peroxide solution to obtain an amorphous titanium peroxide sol. The amorphous titanium peroxide sol is afterward raised to a temperature sufficient to obtain an anatase titanium oxide sol. The resulting anatase titanium oxide sol can thereafter be heated to a temperature sufficient to obtain anatase titanium oxide. The claimed compositions are useful as binders to support the particles of a photocatalyst on a variety of substrates.