This paper describes the design, characterization, and utilization of branched TiO2 nanoarrays sensitized with CdS quantum dots as anodes for photoelectrochemical water splitting. The remarkable photocurrent density (∼4 mA cm(-2) at a potential of 0 V versus Ag/AgCl) and high solar to hydrogen efficiency of the materials obtained were ascribed to the novel branched nanostructure and efficient electron transfer from CdS to TiO2.