AbstractGrowth mechanism of chemically-driven RuO₂ nanowires is explored and used to fabricate three-dimensional RuO₂ branched Au-TiO₂ nanowire electrodes for the photostable solar water oxidation. For the real time structural evolution during the nanowire growth, the amorphous RuO₂ precursors (Ru(OH)₃·H₂O) are heated at 180 ^°C, producing the RuO₂ nanoparticles with the tetragonal crystallographic structure and Ru enriched amorphous phases, observed through the in-situ synchrotron x-ray diffraction and the high-resolution transmission electron microscope images. Growth then proceeds by Ru diffusion to the nanoparticles, followed by the diffusion to the growing surface of the nanowire in oxygen ambient, supported by the nucleation theory. The RuO₂ branched Au-TiO₂ nanowire arrays shows a remarkable enhancement in the photocurrent density by approximately 60% and 200%, in the UV-visible and Visible region, respectively, compared with pristine TiO₂ nanowires. Furthermore, there is no significant decrease in the device’s photoconductance with UV-visible illumination during 1 day, making it possible to produce oxygen gas without the loss of the photoactvity.