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Pt monolayer coating on complex network substrate with high catalytic activity for the hydrogen evolution reaction.

Li M, Ma Q, Zi W, Liu X, Zhu X, Liu SF - Sci Adv (2015)

Bottom Line: A thin underlayer of Ag or Au is found to be necessary to cover a very reactive Ni substrate to ensure complete-monolayer Pt coverage; otherwise, only an incomplete monolayer is formed.Moreover, the Pt monolayer is found to work as well as a thick Pt film for catalytic reactions.This development may pave a way to fabricating a high-activity Pt catalyst with minimal Pt usage.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory for Applied Surface and Colloid Chemistry, National Ministry of Education, Institute for Advanced Energy Materials, School of Materials Science and Engineering, Shaanxi Normal University, Xi'an 710062, China.

ABSTRACT
A deposition process has been developed to fabricate a complete-monolayer Pt coating on a large-surface-area three-dimensional (3D) Ni foam substrate using a buffer layer (Ag or Au) strategy. The quartz crystal microbalance, current density analysis, cyclic voltammetry integration, and X-ray photoelectron spectroscopy results show that the monolayer deposition process accomplishes full coverage on the substrate and the deposition can be controlled to a single atomic layer thickness. To our knowledge, this is the first report on a complete-monolayer Pt coating on a 3D bulk substrate with complex fine structures; all prior literature reported on submonolayer or incomplete-monolayer coating. A thin underlayer of Ag or Au is found to be necessary to cover a very reactive Ni substrate to ensure complete-monolayer Pt coverage; otherwise, only an incomplete monolayer is formed. Moreover, the Pt monolayer is found to work as well as a thick Pt film for catalytic reactions. This development may pave a way to fabricating a high-activity Pt catalyst with minimal Pt usage.

No MeSH data available.


Sequential deposition of Pt monoatomic layers by pulsed electrodeposition in a pH 4 solution.(A) Current density and potential versus time plot for Pt monolayer deposition on 3D Ni foam substrate using the sequential technique. (B) Mass and potential change during the sequential deposition of Pt monolayers using QCM on an Au-coated quartz crystal substrate. (C) Voltammetry curve for the deposition of Pt on the Au NF/Ni foam surface by using a pulsed potential waveform in 0.5 M NaCl and 3 mM K2PtCl4 solution. Sweep rate, 50 mV s−1. (D) Illustration of self-terminating Pt deposition. Inset: Scanning electron microscopy image of Ni foam.
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Figure 2: Sequential deposition of Pt monoatomic layers by pulsed electrodeposition in a pH 4 solution.(A) Current density and potential versus time plot for Pt monolayer deposition on 3D Ni foam substrate using the sequential technique. (B) Mass and potential change during the sequential deposition of Pt monolayers using QCM on an Au-coated quartz crystal substrate. (C) Voltammetry curve for the deposition of Pt on the Au NF/Ni foam surface by using a pulsed potential waveform in 0.5 M NaCl and 3 mM K2PtCl4 solution. Sweep rate, 50 mV s−1. (D) Illustration of self-terminating Pt deposition. Inset: Scanning electron microscopy image of Ni foam.

Mentions: Figure 2 demonstrates the effectiveness of monolayer deposition. Figure 2A shows the current density and potential changes for five electroplating cycles on a complex 3D Ni foam substrate with an Au NF buffer (see the Supplementary Materials for experimental details). The solid curve is for current density (left axis) and the dashed line (right axis) is for plating voltage. When the voltage was set at −0.4 VSCE (volts versus a saturated calomel electrode), the current density increased from −4.4 to ~0 mA cm−2 in 0.2 s, signifying that the deposition cycle was completed. The current density then stabilized even though the plating voltage was maintained at −0.4 VSCE for an extended period of time, demonstrating that the deposition was completely terminated. When the voltage was set to 0 VSCE, the current density first jumped to ~4.4 mA cm−2 and then quickly dropped to 0, signifying that the adsorbed hydrogen layer was instantly desorbed to release a fresh Pt surface. Afterward, as soon as the potential was set to −0.4 VSCE, another cycle of deposition was started, and the previous cycle was repeated.


Pt monolayer coating on complex network substrate with high catalytic activity for the hydrogen evolution reaction.

Li M, Ma Q, Zi W, Liu X, Zhu X, Liu SF - Sci Adv (2015)

Sequential deposition of Pt monoatomic layers by pulsed electrodeposition in a pH 4 solution.(A) Current density and potential versus time plot for Pt monolayer deposition on 3D Ni foam substrate using the sequential technique. (B) Mass and potential change during the sequential deposition of Pt monolayers using QCM on an Au-coated quartz crystal substrate. (C) Voltammetry curve for the deposition of Pt on the Au NF/Ni foam surface by using a pulsed potential waveform in 0.5 M NaCl and 3 mM K2PtCl4 solution. Sweep rate, 50 mV s−1. (D) Illustration of self-terminating Pt deposition. Inset: Scanning electron microscopy image of Ni foam.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
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getmorefigures.php?uid=PMC4643788&req=5

Figure 2: Sequential deposition of Pt monoatomic layers by pulsed electrodeposition in a pH 4 solution.(A) Current density and potential versus time plot for Pt monolayer deposition on 3D Ni foam substrate using the sequential technique. (B) Mass and potential change during the sequential deposition of Pt monolayers using QCM on an Au-coated quartz crystal substrate. (C) Voltammetry curve for the deposition of Pt on the Au NF/Ni foam surface by using a pulsed potential waveform in 0.5 M NaCl and 3 mM K2PtCl4 solution. Sweep rate, 50 mV s−1. (D) Illustration of self-terminating Pt deposition. Inset: Scanning electron microscopy image of Ni foam.
Mentions: Figure 2 demonstrates the effectiveness of monolayer deposition. Figure 2A shows the current density and potential changes for five electroplating cycles on a complex 3D Ni foam substrate with an Au NF buffer (see the Supplementary Materials for experimental details). The solid curve is for current density (left axis) and the dashed line (right axis) is for plating voltage. When the voltage was set at −0.4 VSCE (volts versus a saturated calomel electrode), the current density increased from −4.4 to ~0 mA cm−2 in 0.2 s, signifying that the deposition cycle was completed. The current density then stabilized even though the plating voltage was maintained at −0.4 VSCE for an extended period of time, demonstrating that the deposition was completely terminated. When the voltage was set to 0 VSCE, the current density first jumped to ~4.4 mA cm−2 and then quickly dropped to 0, signifying that the adsorbed hydrogen layer was instantly desorbed to release a fresh Pt surface. Afterward, as soon as the potential was set to −0.4 VSCE, another cycle of deposition was started, and the previous cycle was repeated.

Bottom Line: A thin underlayer of Ag or Au is found to be necessary to cover a very reactive Ni substrate to ensure complete-monolayer Pt coverage; otherwise, only an incomplete monolayer is formed.Moreover, the Pt monolayer is found to work as well as a thick Pt film for catalytic reactions.This development may pave a way to fabricating a high-activity Pt catalyst with minimal Pt usage.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory for Applied Surface and Colloid Chemistry, National Ministry of Education, Institute for Advanced Energy Materials, School of Materials Science and Engineering, Shaanxi Normal University, Xi'an 710062, China.

ABSTRACT
A deposition process has been developed to fabricate a complete-monolayer Pt coating on a large-surface-area three-dimensional (3D) Ni foam substrate using a buffer layer (Ag or Au) strategy. The quartz crystal microbalance, current density analysis, cyclic voltammetry integration, and X-ray photoelectron spectroscopy results show that the monolayer deposition process accomplishes full coverage on the substrate and the deposition can be controlled to a single atomic layer thickness. To our knowledge, this is the first report on a complete-monolayer Pt coating on a 3D bulk substrate with complex fine structures; all prior literature reported on submonolayer or incomplete-monolayer coating. A thin underlayer of Ag or Au is found to be necessary to cover a very reactive Ni substrate to ensure complete-monolayer Pt coverage; otherwise, only an incomplete monolayer is formed. Moreover, the Pt monolayer is found to work as well as a thick Pt film for catalytic reactions. This development may pave a way to fabricating a high-activity Pt catalyst with minimal Pt usage.

No MeSH data available.