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Structural Evolution of Chemically-Driven RuO2 Nanowires and 3-Dimensional Design for Photo-Catalytic Applications.

Park J, Lee JW, Ye BU, Chun SH, Joo SH, Park H, Lee H, Jeong HY, Kim MH, Baik JM - Sci Rep (2015)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: School of Materials Science and Engineering, KIST-UNIST-Ulsan Center for Convergent Materials, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Republic of Korea.

ABSTRACT
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.

No MeSH data available.


Related in: MedlinePlus

(a) Photocurrent versus potential characteristics of 0.5 M Na2SO4 (pH 7.2) electrolyte under AM 1.5 light illumination measured against the Ag/AgCl electrode with 30 mV/s scan rate. (b) Photocurrent density for chopped full spectrum (AM 1.5G) and visible illumination (λ > 420 nm long pass filter with AM 1.5G) at 1.62 V vs. RHE. (c) The quantity of evolved oxygen (red dots) measured (gas-chromatographically) as a function of time. The photocurrent simultaneously recorded with light illumination of white light (AM 1.5G) at 1.23 V vs. RHE.
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f5: (a) Photocurrent versus potential characteristics of 0.5 M Na2SO4 (pH 7.2) electrolyte under AM 1.5 light illumination measured against the Ag/AgCl electrode with 30 mV/s scan rate. (b) Photocurrent density for chopped full spectrum (AM 1.5G) and visible illumination (λ > 420 nm long pass filter with AM 1.5G) at 1.62 V vs. RHE. (c) The quantity of evolved oxygen (red dots) measured (gas-chromatographically) as a function of time. The photocurrent simultaneously recorded with light illumination of white light (AM 1.5G) at 1.23 V vs. RHE.

Mentions: The PEC performance of the TiO2-based photoelectrodes was examined in a three-electrode configuration with Ag/AgCl as the reference electrode and a Pt wire as the counter electrode. Figure 5a shows the photocurrent-potential characteristics of the TiO2 nanowires, AuNPs decorated TiO2 nanowires, and RuO2 branched AuNPs-TiO2 nanowires recorded in 0.5 M Na2SO4 electrolyte (pH = 7.2) under AM 1.5G illumination of 100 mW/cm2. The dark scans revealed a small background current of ~2 × 10−3 mA/cm2, negligible compared to the photocurrent densities of all photoelectrodes. Upon illumination with white light, the pristine TiO2 nanowires electrodes show a photocurrent density of 0.673 mA/cm2 at 1.23 V vs. RHE (0.61 V vs. Ag/AgCl). As AuNPs are decorated onto the nanowires, the photocurrent density increases to 0.909 mA/cm2 at the same potential, associated with the surface plasmonic resonance effect of the AuNPs28. It was also observed that under visible-light illumination, the photocurrent density of AuNPs-TiO2 nanowires was increased by 1.93 times, in comparison with pristine TiO2 nanowires, obtained by adding a 420 nm long-pass filter to the white source, as shown in Fig. 5b. The formation of RuO2 nanowires on AuNPs-TiO2 nanowires increases the photocurrent density to 1.052 mA/cm2, around 56% enhancement, compared with pristine TiO2 nanowires. It is believed that the RuO2 promotes the electron transfer to the AuNPs due to the high catalytic properties for the water oxidation and the efficient hole injection to RuO2 to AuNPs, catalyzing the oxygen evolution (Supplementary Fig. S2). This process is prominent seen under visible light. We also observed that the photocurrent of the branched nanowires significantly increased over approximately 0.7 V vs. RHE, compared to that of the AuNPs-TiO2 nanowires, with a slight shift in the onset voltage. This may be related to the flat band voltage as 0.41 eV of the work function difference between Au and RuO2. The slight shift in the onset voltage may also be ascribed to the low overpotential on the Au-TiO2 nanowires associated with the oxygen reduction2930.


Structural Evolution of Chemically-Driven RuO2 Nanowires and 3-Dimensional Design for Photo-Catalytic Applications.

Park J, Lee JW, Ye BU, Chun SH, Joo SH, Park H, Lee H, Jeong HY, Kim MH, Baik JM - Sci Rep (2015)

(a) Photocurrent versus potential characteristics of 0.5 M Na2SO4 (pH 7.2) electrolyte under AM 1.5 light illumination measured against the Ag/AgCl electrode with 30 mV/s scan rate. (b) Photocurrent density for chopped full spectrum (AM 1.5G) and visible illumination (λ > 420 nm long pass filter with AM 1.5G) at 1.62 V vs. RHE. (c) The quantity of evolved oxygen (red dots) measured (gas-chromatographically) as a function of time. The photocurrent simultaneously recorded with light illumination of white light (AM 1.5G) at 1.23 V vs. RHE.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493639&req=5

f5: (a) Photocurrent versus potential characteristics of 0.5 M Na2SO4 (pH 7.2) electrolyte under AM 1.5 light illumination measured against the Ag/AgCl electrode with 30 mV/s scan rate. (b) Photocurrent density for chopped full spectrum (AM 1.5G) and visible illumination (λ > 420 nm long pass filter with AM 1.5G) at 1.62 V vs. RHE. (c) The quantity of evolved oxygen (red dots) measured (gas-chromatographically) as a function of time. The photocurrent simultaneously recorded with light illumination of white light (AM 1.5G) at 1.23 V vs. RHE.
Mentions: The PEC performance of the TiO2-based photoelectrodes was examined in a three-electrode configuration with Ag/AgCl as the reference electrode and a Pt wire as the counter electrode. Figure 5a shows the photocurrent-potential characteristics of the TiO2 nanowires, AuNPs decorated TiO2 nanowires, and RuO2 branched AuNPs-TiO2 nanowires recorded in 0.5 M Na2SO4 electrolyte (pH = 7.2) under AM 1.5G illumination of 100 mW/cm2. The dark scans revealed a small background current of ~2 × 10−3 mA/cm2, negligible compared to the photocurrent densities of all photoelectrodes. Upon illumination with white light, the pristine TiO2 nanowires electrodes show a photocurrent density of 0.673 mA/cm2 at 1.23 V vs. RHE (0.61 V vs. Ag/AgCl). As AuNPs are decorated onto the nanowires, the photocurrent density increases to 0.909 mA/cm2 at the same potential, associated with the surface plasmonic resonance effect of the AuNPs28. It was also observed that under visible-light illumination, the photocurrent density of AuNPs-TiO2 nanowires was increased by 1.93 times, in comparison with pristine TiO2 nanowires, obtained by adding a 420 nm long-pass filter to the white source, as shown in Fig. 5b. The formation of RuO2 nanowires on AuNPs-TiO2 nanowires increases the photocurrent density to 1.052 mA/cm2, around 56% enhancement, compared with pristine TiO2 nanowires. It is believed that the RuO2 promotes the electron transfer to the AuNPs due to the high catalytic properties for the water oxidation and the efficient hole injection to RuO2 to AuNPs, catalyzing the oxygen evolution (Supplementary Fig. S2). This process is prominent seen under visible light. We also observed that the photocurrent of the branched nanowires significantly increased over approximately 0.7 V vs. RHE, compared to that of the AuNPs-TiO2 nanowires, with a slight shift in the onset voltage. This may be related to the flat band voltage as 0.41 eV of the work function difference between Au and RuO2. The slight shift in the onset voltage may also be ascribed to the low overpotential on the Au-TiO2 nanowires associated with the oxygen reduction2930.

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: School of Materials Science and Engineering, KIST-UNIST-Ulsan Center for Convergent Materials, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798, Republic of Korea.

ABSTRACT
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.

No MeSH data available.


Related in: MedlinePlus