Limits...
Polyhedral Palladium-Silver Alloy Nanocrystals as Highly Active and Stable Electrocatalysts for the Formic Acid Oxidation Reaction.

Fu GT, Liu C, Zhang Q, Chen Y, Tang YW - Sci Rep (2015)

Bottom Line: Polyhedral noble-metal nanocrystals have received much attention and wide applications as electrical and optical devices as well as catalysts.In this work, a straightforward and effective hydrothermal route for the controllable synthesis of the high-quality Pd-Ag alloy polyhedrons with uniform size is presented.As a preliminary electrochemical application, the Pd-Ag alloy polyhedrons are applied in the formic acid oxidation reaction, which shows higher electrocatalytic activity and stability than commercially available Pd black due to the "synergistic effects" between Pd and Ag atoms.

View Article: PubMed Central - PubMed

Affiliation: Jiangsu Key Laboratory of New Power Batteries, Jiangsu Collaborative Innovation Center of Biomedical Functional Materials, School of Chemistry and Materials Science, Nanjing Normal University, Nanjing 210023, P. R. China.

ABSTRACT
Polyhedral noble-metal nanocrystals have received much attention and wide applications as electrical and optical devices as well as catalysts. In this work, a straightforward and effective hydrothermal route for the controllable synthesis of the high-quality Pd-Ag alloy polyhedrons with uniform size is presented. The morphology, composition and structure of the Pd-Ag alloy polyhedrons are fully characterized by the various physical techniques, demonstrating the Pd-Ag alloy polyhedrons are highly alloying. The formation/growth mechanisms of the Pd-Ag alloy polyhedrons are explored and discussed based on the experimental observations and discussions. As a preliminary electrochemical application, the Pd-Ag alloy polyhedrons are applied in the formic acid oxidation reaction, which shows higher electrocatalytic activity and stability than commercially available Pd black due to the "synergistic effects" between Pd and Ag atoms.

No MeSH data available.


(A) Cyclic voltammograms of the Pd–Ag alloy polyhedrons and commercial Pd black in N2-saturated 0.5 M H2SO4 solution at a scan rate of 50 mV s−1. (B,D) Mass-normalized and ECSA-normalized cyclic voltammograms of the Pd–Ag alloy polyhedrons and commercial Pd black in N2-saturated 0.5 M H2SO4 + 0.5 M HCOOH solution at a scan rate of 50 mV s−1, respectively. (C) Tafel plots of log I vs. potential for the FAOR on the Pd–Ag alloy polyhedrons and commercial Pd black in electrochemical control area. (E) The TOF values of the Pd–Ag alloy polyhedrons and commercial Pd black at 0.15 V potential. (F) Chronoamperometry curves of the Pd–Ag alloy polyhedrons and commercial Pd black in N2-saturated 0.5 M H2SO4 + 0.5 M HCOOH solution for 4000 s at 0.15 V potential.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4556982&req=5

f5: (A) Cyclic voltammograms of the Pd–Ag alloy polyhedrons and commercial Pd black in N2-saturated 0.5 M H2SO4 solution at a scan rate of 50 mV s−1. (B,D) Mass-normalized and ECSA-normalized cyclic voltammograms of the Pd–Ag alloy polyhedrons and commercial Pd black in N2-saturated 0.5 M H2SO4 + 0.5 M HCOOH solution at a scan rate of 50 mV s−1, respectively. (C) Tafel plots of log I vs. potential for the FAOR on the Pd–Ag alloy polyhedrons and commercial Pd black in electrochemical control area. (E) The TOF values of the Pd–Ag alloy polyhedrons and commercial Pd black at 0.15 V potential. (F) Chronoamperometry curves of the Pd–Ag alloy polyhedrons and commercial Pd black in N2-saturated 0.5 M H2SO4 + 0.5 M HCOOH solution for 4000 s at 0.15 V potential.

Mentions: The electrocatalytic activity of the Pd–Ag alloy polyhedrons for the FAOR was evaluated in an electrochemical measurement system. For comparison, the commercial state-of-the-art Pd black was also measured as reference materials under the same conditions. The electrochemical properties of the Pd–Ag alloy polyhedrons and commercial Pd black are investigated by cyclic voltammetry in N2-purged 0.5 M H2SO4 solution (Fig. 5A). No electrochemical dissolution of Ag is found, indicating that alloying with Pd can greatly enhance the electrochemical stability of Ag. In addition, after an additional 10 CV cycles, the Pd/Ag atom ratio (50.30: 49.70) in Pd–Ag alloy polyhedrons is close to their initial value (48.10 and 51.90) (Figure S6A), and the the morphology of Pd–Ag alloy polyhedrons essentially remains (Figure S6B). The results further confirm that the introduction of Pd enhances the electrochemical stability of Ag. The hydrogen adsorption peak of the Pd–Ag alloy polyhedrons is much larger than that of the commercial Pd black, indicating that the Pd–Ag alloy polyhedrons may have a bigger electrochemically active surface area (ECSA) than Pd black. Based on the charge of reduction monolayer in Pd oxide region (see Experimental section for details), the ECSA of the Pd–Ag alloy polyhedrons is calculated to be 9.62 m2g−1, which is larger than that of commercial Pd black (6.88 m2g−1). The larger ECSA for the Pd–Ag alloy polyhedrons is most likely due to the smaller size and better dispersion of the Pd–Ag alloy polyhedrons than commercial Pd black. Meanwhile, it is observed that the formation potential of oxide on the Pd–Ag alloy polyhedrons negatively shifts ca. 35 mV compared to that of Pd black, indicating the Pd–Ag alloy polyhedrons can afford –OH species at lower potential.


Polyhedral Palladium-Silver Alloy Nanocrystals as Highly Active and Stable Electrocatalysts for the Formic Acid Oxidation Reaction.

Fu GT, Liu C, Zhang Q, Chen Y, Tang YW - Sci Rep (2015)

(A) Cyclic voltammograms of the Pd–Ag alloy polyhedrons and commercial Pd black in N2-saturated 0.5 M H2SO4 solution at a scan rate of 50 mV s−1. (B,D) Mass-normalized and ECSA-normalized cyclic voltammograms of the Pd–Ag alloy polyhedrons and commercial Pd black in N2-saturated 0.5 M H2SO4 + 0.5 M HCOOH solution at a scan rate of 50 mV s−1, respectively. (C) Tafel plots of log I vs. potential for the FAOR on the Pd–Ag alloy polyhedrons and commercial Pd black in electrochemical control area. (E) The TOF values of the Pd–Ag alloy polyhedrons and commercial Pd black at 0.15 V potential. (F) Chronoamperometry curves of the Pd–Ag alloy polyhedrons and commercial Pd black in N2-saturated 0.5 M H2SO4 + 0.5 M HCOOH solution for 4000 s at 0.15 V potential.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4556982&req=5

f5: (A) Cyclic voltammograms of the Pd–Ag alloy polyhedrons and commercial Pd black in N2-saturated 0.5 M H2SO4 solution at a scan rate of 50 mV s−1. (B,D) Mass-normalized and ECSA-normalized cyclic voltammograms of the Pd–Ag alloy polyhedrons and commercial Pd black in N2-saturated 0.5 M H2SO4 + 0.5 M HCOOH solution at a scan rate of 50 mV s−1, respectively. (C) Tafel plots of log I vs. potential for the FAOR on the Pd–Ag alloy polyhedrons and commercial Pd black in electrochemical control area. (E) The TOF values of the Pd–Ag alloy polyhedrons and commercial Pd black at 0.15 V potential. (F) Chronoamperometry curves of the Pd–Ag alloy polyhedrons and commercial Pd black in N2-saturated 0.5 M H2SO4 + 0.5 M HCOOH solution for 4000 s at 0.15 V potential.
Mentions: The electrocatalytic activity of the Pd–Ag alloy polyhedrons for the FAOR was evaluated in an electrochemical measurement system. For comparison, the commercial state-of-the-art Pd black was also measured as reference materials under the same conditions. The electrochemical properties of the Pd–Ag alloy polyhedrons and commercial Pd black are investigated by cyclic voltammetry in N2-purged 0.5 M H2SO4 solution (Fig. 5A). No electrochemical dissolution of Ag is found, indicating that alloying with Pd can greatly enhance the electrochemical stability of Ag. In addition, after an additional 10 CV cycles, the Pd/Ag atom ratio (50.30: 49.70) in Pd–Ag alloy polyhedrons is close to their initial value (48.10 and 51.90) (Figure S6A), and the the morphology of Pd–Ag alloy polyhedrons essentially remains (Figure S6B). The results further confirm that the introduction of Pd enhances the electrochemical stability of Ag. The hydrogen adsorption peak of the Pd–Ag alloy polyhedrons is much larger than that of the commercial Pd black, indicating that the Pd–Ag alloy polyhedrons may have a bigger electrochemically active surface area (ECSA) than Pd black. Based on the charge of reduction monolayer in Pd oxide region (see Experimental section for details), the ECSA of the Pd–Ag alloy polyhedrons is calculated to be 9.62 m2g−1, which is larger than that of commercial Pd black (6.88 m2g−1). The larger ECSA for the Pd–Ag alloy polyhedrons is most likely due to the smaller size and better dispersion of the Pd–Ag alloy polyhedrons than commercial Pd black. Meanwhile, it is observed that the formation potential of oxide on the Pd–Ag alloy polyhedrons negatively shifts ca. 35 mV compared to that of Pd black, indicating the Pd–Ag alloy polyhedrons can afford –OH species at lower potential.

Bottom Line: Polyhedral noble-metal nanocrystals have received much attention and wide applications as electrical and optical devices as well as catalysts.In this work, a straightforward and effective hydrothermal route for the controllable synthesis of the high-quality Pd-Ag alloy polyhedrons with uniform size is presented.As a preliminary electrochemical application, the Pd-Ag alloy polyhedrons are applied in the formic acid oxidation reaction, which shows higher electrocatalytic activity and stability than commercially available Pd black due to the "synergistic effects" between Pd and Ag atoms.

View Article: PubMed Central - PubMed

Affiliation: Jiangsu Key Laboratory of New Power Batteries, Jiangsu Collaborative Innovation Center of Biomedical Functional Materials, School of Chemistry and Materials Science, Nanjing Normal University, Nanjing 210023, P. R. China.

ABSTRACT
Polyhedral noble-metal nanocrystals have received much attention and wide applications as electrical and optical devices as well as catalysts. In this work, a straightforward and effective hydrothermal route for the controllable synthesis of the high-quality Pd-Ag alloy polyhedrons with uniform size is presented. The morphology, composition and structure of the Pd-Ag alloy polyhedrons are fully characterized by the various physical techniques, demonstrating the Pd-Ag alloy polyhedrons are highly alloying. The formation/growth mechanisms of the Pd-Ag alloy polyhedrons are explored and discussed based on the experimental observations and discussions. As a preliminary electrochemical application, the Pd-Ag alloy polyhedrons are applied in the formic acid oxidation reaction, which shows higher electrocatalytic activity and stability than commercially available Pd black due to the "synergistic effects" between Pd and Ag atoms.

No MeSH data available.