Growth 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.
Bibliographical noteFunding Information:
This work was supported the Pioneer Research Center Program (2013M3C1A3063602) of the National Research Foundation of Korea (NRF) grant funded by the Ministry of Science, ICT & Future Planning (MSIP), and by Basic Science Program through the National Research Foundation of Korea (NRF) funded by MEST (Nos. 2014R1A1A2059791 for MHK). This work was also financially supported by the KIST-UNIST partnership program (2V03870/2V03880) and equivalently by the 2014 Research Fund (1.140019.01) of UNIST (Ulsan National Institute of Science and Technology). We are very thankful to Prof. Suk-Bin Lee (UNIST) for great contribution in this paper.
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