Hydrogen trititanate (H2Ti3O7) nanorods were synthesized by using a hydrothermal method. The transformation of the crystal structure from H2Ti3O7 to TiO2 occurred into either single crystalline TiO2 (B) [calcined at 400 or 450 °C] or bicrystalline TiO2 (B) with anatase phases [calcined at 500 or 550 °C] during a calcination process. Calcination temperature from 450 to 550 °C induced both phase transformation and formation of large size nanocavities, and the changes in the nanorods morphology were confirmed using HRTEM/TEM images. Nanocomposites of Cu2O/TiO2 nanorods with different copper loading (CuxTNR) were prepared by using the wet impregnation method with TiO2 nanorods [calcined at 500 °C] and copper nitrate as copper source. The structural, optical, surface elemental and morphological properties of the synthesized catalysts were extensively characterized. Solar photocatalytic hydrogen (H2) production experiment was carried out with aqueous-glycerol solution for 4 h. The photocatalytic activity of TiO2 nanorods that are calcined at 500 °C exhibited very high rate of H2 production, is ascribed to the improved separation of electron/hole pairs and catalytic activity at bicrystalline TiO2 surface. For the first-time, we have achieved the higher rate of H2 (50,339 µmol h−1 g−1cat) production under the set of the optimized conditions using Cu1.5TNR nanorods containing nanocavities as catalyst under solar irradiation. This enhancement in the activity can be attributed to the desirable absorption of UV–visible light in natural solar spectrum and minimization of the recombination of electron–hole pairs, multiple internal reflection of light within nanocavities, which improved the surface–interface reactions. The present study clearly demonstrated that Cu loaded on titania nanorods containing nanocavities were found to be more efficient and promising photocatalyst for H2 production under solar light irradiation.