The paper highlights less-common properties of nanosized WO 3 thin films which make it possible to achieve photolysis in CuCl films via the use of a CuCl–WO 3 double-layer structure. The WO 3 film provides first photoinduced detachment of hydrogen atoms from organic molecules adsorbed on the oxide surface; the hydrogen atoms, being transferred into WO 3 , turn into electrons and protons which migrate then to the CuCl film forming sensitizing centres on the halide surface being illuminated simultaneously with the illumination of the WO 3 surface. This in turn gives rise to photolysis in the CuCl films, which does not occur without the hydrogen sensitization. The nanosized WO 3 film makes it possible to trigger two famous surface photochemical reactions, first proton-coupled electron transfer between the hydrogen-donor molecules and the oxide surface, and then the photolysis of the halide, which radically changes the optical parameters of both the WO 3 and the CuCl films.