In order to further enhance photoeletrocatalytic reactivity, it is desirable to develop a facile and effective technique to obtain high quality Pd@TNTAs with homogeneous dispersion and small enough particle size down to few of nm Pd quantum dots (QDs) on the geometrically-ordered TiO2 nanotube arraysIn this paper we report an investigation on the Pd QDs sensitized TiO2 nanotube arrays (Pd/TiO2NTs) and their excellent performance in hydrogen production by photoelectrocatalytic water splitting. The Pd QDs are found uniformly distributed on both inside and outside TiO2 nanotubes with average size from ~2.5 to ~4nm with a very narrow size distribution. Uniform coverage of Pd QDs from the pore bottom to top has been achieved. The obtained nanocomposites showed an incident photon-to-current conversion efficiency (IPCE) value of nearly 100% and a significantly enhanced photocatalytic hydrogen generation rate of about 592 mmol•h-1•cm-2 under 320 mW/cm2 irradiation. These results clearly demonstrate that Pd QDs sensitized TiO2 nanotube arrays can remarkably improve the photocatalytic efficiency.