The invention pertains to a device for generating aqueous chlorine dioxide solutions when the device is contacted with liquid water. The device comprises an alkali metal or alkaline earth metal chlorite, e.g., sodium chlorite, and a chemical reagent comprising an acid or a material capable of releasing an acid upon exposure to liquid water, e.g., sodium bisulfate. The chlorite and the reagent are either combined as a mixture or are disposed as separate components adhered to the surface of one or more substrates. Upon exposure to liquid water, the chlorite and the reagent produce boundary layers. The chlorite and the reagent are disposed upon, and adhered to, the surface(s) of the substrates in a manner such that upon exposure to liquid water, the chlorite boundary layer comes into contact with the reagent boundary layer to thereby produce an aqueous chlorine dioxide solution.