NOVELTY - A photocatalytic structure (S1) comprises: substrate; first layer containing aligned array of tungsten oxide nanorods deposited on the substrate; and a second layer deposited on each of the nanorods of the array of the first layer, where the second layer contains titanium oxide.    USE - As a photocatalytic structure used to split water to produce hydrogen, and to split carbon dioxide (claimed).    ADVANTAGE - The structure allows the use of significantly less photocatalytic material (TiO2) than with traditional single layered photocatalytic materials; and shows significant photocatalytic enhancement (up to 370 times) over amorphous TiO2 thin films, and anatase TiO2 films (7 times). In the structure, by combining TiO2 with WO3, the excitation spectra is shifted out from the UV region towards the visible wavelength region, that allows a larger spectra of light to initiate the photoreactions. The structure includes WO3/TiO2 two-layer and core-shell nanorod arrays where the surface density of the separated charges is maximized by maximizing the WO3-TiO2 interfacial area, thus increases the decay rate significantly.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) making (M1) photocatalytic structure involving providing a substrate; depositing a first layer on the substrate, where the first layer comprises an aligned nanorod array, where the nanorods of the first layer are made of a material selected from tungsten oxide (WO3) and titanium oxide (TiO2); and depositing a second layer on each of the nanorods of the array of the first layer, where the nanorods of the first layer are made of a material selected from WO3 and TiO2;    (2) structure (S2) comprising a substrate having TiO2 nanorods disposed on the substrate, where the TiO2 nanorods have a length of 800-1100 nm and a width of 45-400 nm, where the density of the nanorods is 2-65x 106 mm2, and the nanorods are tilted from the substrate at an angle of 40-65 degrees from substrate normal;    (3) splitting H2O to generate H2 involving providing the photoelectrochemical structure (S2); introducing an aqueous solution to the photoelectrochemical structure so that the aqueous solution contacts the TiO2 nanorods; and exposing the photoelectrochemical structure to a light source, where the aqueous solution and the photoelectrochemical structure interact to produce H2 from the aqueous solution;    (4) making (M2) structure involving depositing TiO2 on a substrate at a rate of 0.2-0.6 nm/s with the substrate positioned at 50-89 degrees from the incident evaporation direction with an azimuthal rotation speed of 0.4-0.6 revolution per second (rev/s), the temperature is 25 degrees C, forming TiO2 nanorods, and annealing the TiO2 nanorods at 200-600 degrees C;    (5) structure (S3) comprising a nanostructured zinc oxide (ZnO) thin film disposed on a substrate, where the nanostructured ZnO thin film has a surface feature selected from thin film with grain size features of 150-250 nm; thin film with a fishscale morphology, where each fishscale feature is 900x 450 nm; and nanoporous, interconnected network of spherical nanoparticles, where each nanoparticle is 15-40 nm in diameter;    (6) making (M3) structure involving depositing zinc oxide (ZnO) on a substrate at a rate of 0.1-0.6 nm/second with the substrate positioned at 50-89 degrees from the incident evaporation direction with an azimuthal rotation speed of 0.4-0.6 rev/s, the temperature of 25 degrees C; forming ZnO nanorods; and annealing the ZnO nanorods at 100-650 degrees C;    (7) splitting H2O to generate H2 involving deposition nanostructured ZnO thin film on a substrate, where the nanostructured ZnO thin film has a surface feature selected from thin film with grain size features of 150-250 nm, a thin film with fishscale morphology, where each fishscale feature is 900x 450 nm, and nanoporous, interconnected network of spherical nanoparticles, where each nanoparticle is 15-40 nm in diameter; introducing an aqueous solution to the photoelectrochemical structure so that the aqueous solution contacts the ZnO thin film; and exposing the photoelectrochemical structure to a light source, where the aqueous solution and the photoelectrochemical structure interact to produce H2 from the aqueous solution.