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A facile approach to prepare silicon-based Pt-Ag tubular dendritic nano-forests (tDNFs) for solar-light-enhanced methanol oxidation reaction.

Lin CT, Shiao MH, Chang MN, Chu N, Chen YW, Peng YH, Liao BH, Huang HJ, Hsiao CN, Tseng FG - Nanoscale Res Lett (2015)

Bottom Line: In the first GRR, a homogeneous layer of silver dendritic nano-forests (DNFs) with 10 μm in thickness was grown on Si wafer in 5 min in silver nitride (AgNO3) and buffer oxide etchant (BOE) solution.In the second GRR, we utilized chloroplatinic acid (H2PtCl6) as the precursor for platinum (Pt) deposition to further transform the prepared Ag DNFs into Pt-Ag tDNFs.Current results provide a cost-effective and facile approach to prepare solar-driven metallic electrodes potentially applicable to photo-electro-chemical fuel cells.

View Article: PubMed Central - PubMed

Affiliation: Instrument Technology Research Center, National Applied Research Laboratories, Hsinchu, 300 Taiwan ; Department of Engineering and System Science, National Tsing Hua University, Hsinchu, 300 Taiwan.

ABSTRACT
In this paper, a facile two-step Galvanic replacement reaction (GRR) is proposed to prepare Pt-Ag tubular dendritic nano-forests (tDNFs) in ambient condition for enhancing methanol oxidation reaction (MOR) under solar illumination. In the first GRR, a homogeneous layer of silver dendritic nano-forests (DNFs) with 10 μm in thickness was grown on Si wafer in 5 min in silver nitride (AgNO3) and buffer oxide etchant (BOE) solution. In the second GRR, we utilized chloroplatinic acid (H2PtCl6) as the precursor for platinum (Pt) deposition to further transform the prepared Ag DNFs into Pt-Ag tDNFs. The catalytic performance and solar response of the Pt-Ag tDNFs toward methanol electro-oxidation are also studied by cyclic voltammetry (CV) and chronoamperometry (CA). The methanol oxidation current was boosted by 6.4% under solar illumination on the Pt-Ag tDNFs due to the induced localized surface plasmon resonance (LSPR) on the dendritic structure. Current results provide a cost-effective and facile approach to prepare solar-driven metallic electrodes potentially applicable to photo-electro-chemical fuel cells.

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STEM bright-field image, high-angle annular dark-field STEM image, TEM images, and EDS result. (a) The STEM bright-field image of typical Pt-Ag tDNFs. (b) The high-angle annular dark-field (HAADF) STEM image of the same sample. (c-e) The TEM images in different magnifications of the same sample. (f) The corresponding EDS linear result.
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Fig5: STEM bright-field image, high-angle annular dark-field STEM image, TEM images, and EDS result. (a) The STEM bright-field image of typical Pt-Ag tDNFs. (b) The high-angle annular dark-field (HAADF) STEM image of the same sample. (c-e) The TEM images in different magnifications of the same sample. (f) The corresponding EDS linear result.

Mentions: Figure 4 shows the SEM investigations of typical Pt-Ag tDNFs and the corresponding EDS analysis result. The morphology of the Pt-Ag DNFs basically follows that of the Ag DNFs while the branches were broadened. The composition of Pt was verified by the EDS analysis (Figure 4d). Figure 5 shows the TEM and scanning transmission electron microscope (STEM) images of the Pt-Ag tDNFs. Dark nano-shells (approximately 20 nm in thickness) were found growing along with the fringe of Ag branches in the bright field images (Figure 5a,c,d,e). The nano-shells were found bright in the high-angle annular dark-field (HAADF) images in Figure 5b. Since HAADF images are highly sensitive to atomic-number contrast [35], we hence verified that a thin layer of Pt nano-shell was grown over the whole surface of Ag branches. The tubular nature of Pt-Ag tDNFs was verified by the EDS linear scan in Figure 5f. The main reason of the formation of the hollow structures could be attributed to the difference in diffusion rate between Ag in Pt and Pt in Ag during the GRR process, which is known as the Kirkendell effect [10]. Since the diffusion rate of Ag in Pt is faster than that of Pt in Ag, the voids in Ag domain accumulated to form pores beneath the outer shell and finally occupied the cores of the dendrites [10,21,36]. Besides, several parallel dark lines were observed growing along with the long axis of the composite dendrite in the Ag core region in Figure 5d,e. That provides an evidence to the Kirkendall growth of Pt, which is the main mechanism of the formation of multi-layered metallic nanostructures in GRR [36]. Similarly, hollow Pt-Ag hybrid structures prepared via GRR were also reported by other groups [19-21]. Zhang et al. used GRR to fabricate Pt/Ag hollow nanoboxes for methanol oxidation [19]. Bansal et al. replaced Ag nanocubes with Pt by GRR for H2 evolution reaction [20]. Also, Kim et al. prepared hollow Pt/Ag nanospheres by GRR for the degradation of rhodamine B [21].Figure 4


A facile approach to prepare silicon-based Pt-Ag tubular dendritic nano-forests (tDNFs) for solar-light-enhanced methanol oxidation reaction.

Lin CT, Shiao MH, Chang MN, Chu N, Chen YW, Peng YH, Liao BH, Huang HJ, Hsiao CN, Tseng FG - Nanoscale Res Lett (2015)

STEM bright-field image, high-angle annular dark-field STEM image, TEM images, and EDS result. (a) The STEM bright-field image of typical Pt-Ag tDNFs. (b) The high-angle annular dark-field (HAADF) STEM image of the same sample. (c-e) The TEM images in different magnifications of the same sample. (f) The corresponding EDS linear result.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4385142&req=5

Fig5: STEM bright-field image, high-angle annular dark-field STEM image, TEM images, and EDS result. (a) The STEM bright-field image of typical Pt-Ag tDNFs. (b) The high-angle annular dark-field (HAADF) STEM image of the same sample. (c-e) The TEM images in different magnifications of the same sample. (f) The corresponding EDS linear result.
Mentions: Figure 4 shows the SEM investigations of typical Pt-Ag tDNFs and the corresponding EDS analysis result. The morphology of the Pt-Ag DNFs basically follows that of the Ag DNFs while the branches were broadened. The composition of Pt was verified by the EDS analysis (Figure 4d). Figure 5 shows the TEM and scanning transmission electron microscope (STEM) images of the Pt-Ag tDNFs. Dark nano-shells (approximately 20 nm in thickness) were found growing along with the fringe of Ag branches in the bright field images (Figure 5a,c,d,e). The nano-shells were found bright in the high-angle annular dark-field (HAADF) images in Figure 5b. Since HAADF images are highly sensitive to atomic-number contrast [35], we hence verified that a thin layer of Pt nano-shell was grown over the whole surface of Ag branches. The tubular nature of Pt-Ag tDNFs was verified by the EDS linear scan in Figure 5f. The main reason of the formation of the hollow structures could be attributed to the difference in diffusion rate between Ag in Pt and Pt in Ag during the GRR process, which is known as the Kirkendell effect [10]. Since the diffusion rate of Ag in Pt is faster than that of Pt in Ag, the voids in Ag domain accumulated to form pores beneath the outer shell and finally occupied the cores of the dendrites [10,21,36]. Besides, several parallel dark lines were observed growing along with the long axis of the composite dendrite in the Ag core region in Figure 5d,e. That provides an evidence to the Kirkendall growth of Pt, which is the main mechanism of the formation of multi-layered metallic nanostructures in GRR [36]. Similarly, hollow Pt-Ag hybrid structures prepared via GRR were also reported by other groups [19-21]. Zhang et al. used GRR to fabricate Pt/Ag hollow nanoboxes for methanol oxidation [19]. Bansal et al. replaced Ag nanocubes with Pt by GRR for H2 evolution reaction [20]. Also, Kim et al. prepared hollow Pt/Ag nanospheres by GRR for the degradation of rhodamine B [21].Figure 4

Bottom Line: In the first GRR, a homogeneous layer of silver dendritic nano-forests (DNFs) with 10 μm in thickness was grown on Si wafer in 5 min in silver nitride (AgNO3) and buffer oxide etchant (BOE) solution.In the second GRR, we utilized chloroplatinic acid (H2PtCl6) as the precursor for platinum (Pt) deposition to further transform the prepared Ag DNFs into Pt-Ag tDNFs.Current results provide a cost-effective and facile approach to prepare solar-driven metallic electrodes potentially applicable to photo-electro-chemical fuel cells.

View Article: PubMed Central - PubMed

Affiliation: Instrument Technology Research Center, National Applied Research Laboratories, Hsinchu, 300 Taiwan ; Department of Engineering and System Science, National Tsing Hua University, Hsinchu, 300 Taiwan.

ABSTRACT
In this paper, a facile two-step Galvanic replacement reaction (GRR) is proposed to prepare Pt-Ag tubular dendritic nano-forests (tDNFs) in ambient condition for enhancing methanol oxidation reaction (MOR) under solar illumination. In the first GRR, a homogeneous layer of silver dendritic nano-forests (DNFs) with 10 μm in thickness was grown on Si wafer in 5 min in silver nitride (AgNO3) and buffer oxide etchant (BOE) solution. In the second GRR, we utilized chloroplatinic acid (H2PtCl6) as the precursor for platinum (Pt) deposition to further transform the prepared Ag DNFs into Pt-Ag tDNFs. The catalytic performance and solar response of the Pt-Ag tDNFs toward methanol electro-oxidation are also studied by cyclic voltammetry (CV) and chronoamperometry (CA). The methanol oxidation current was boosted by 6.4% under solar illumination on the Pt-Ag tDNFs due to the induced localized surface plasmon resonance (LSPR) on the dendritic structure. Current results provide a cost-effective and facile approach to prepare solar-driven metallic electrodes potentially applicable to photo-electro-chemical fuel cells.

No MeSH data available.


Related in: MedlinePlus