Supported PtCu alloys have been broadly applied in heterogeneous catalysis and electrocatalysis owing to their excellent catalytic performance and high CO tolerance. It is important to analyze the outermost surface c...Supported PtCu alloys have been broadly applied in heterogeneous catalysis and electrocatalysis owing to their excellent catalytic performance and high CO tolerance. It is important to analyze the outermost surface composition of the supported alloy nanoparticles to understand the nature of the catalytically active sites. In this paper, homogeneous face-centered cubic PtCu nanoparticles with a narrow particle size distribution were successfully fabricated and dispersed on a high-surface-area Ti〇2 powder support. The samples were oxidized and reduced in situ and then introduced into the ultrahigh vacuum chamber to measure the topmost surface composition by high-sensitivity low-energy ion scattering spectroscopy, and to determine the oxidation states of the elements by X-ray photoelectron spectroscopy. The surface composition and morphology, elemental distribu-tion, and oxidation states of the components were found to be significantly affected by the support and treatment conditions. The PtCu is de-alloyed upon oxidation with CuO wetting on the TiO2 sur-face and re-alloyed upon reduction. Phase diagrams of the surface composition and the bulk com-position were plotted and compared for the supported and unsupported materials.展开更多
In this work,we have performed density functional theory(DFT)calculations to investigate the methanol electro‐oxidation reaction(MOR)catalyzed by the Pt,PtCu alloy and Cu.The complex reaction networks,including the i...In this work,we have performed density functional theory(DFT)calculations to investigate the methanol electro‐oxidation reaction(MOR)catalyzed by the Pt,PtCu alloy and Cu.The complex reaction networks,including the intermediate dehydrogenation,water dissociation and anti‐poison reaction steps,are systematically investigated to explore the mechanisms.At the standard condition of pH=0 and zero potential,for Cu,most dehydrogenation steps along the favorable pathway are endergonic,making it less active in MOR.For the Pt and PtCu alloy,their dehydrogenation steps are mainly exergonic,but the formed CO intermediate binds too tightly on Pt,that can accumulate on active sites to poison the electro‐catalyst.The CO can be consumed by the thermodynamic reaction with OH*,which comes from water dissociation.DFT calculation shows alloying the Pt with Cu could not only reduce the free energy barrier for binding between CO*and OH*,but also assist the water dissociation to produce more OH*for that anti‐poison reaction.That makes the PtCu alloy more active than the pure Pt electrode in experiment.The results reveal the importance of anti‐poison reaction and water dissociation in MOR,which could be applied to the rational design of more active alloy electro‐catalysts in future.展开更多
In this paper, we reported a solvothermal method for the synthesis of octahedral Pt-Cu bimetallic alloy nanocrystals （NCs） with tunable composition. Inspired by the result from our previous exploration on octahedral...In this paper, we reported a solvothermal method for the synthesis of octahedral Pt-Cu bimetallic alloy nanocrystals （NCs） with tunable composition. Inspired by the result from our previous exploration on octahedral Pt-Cu alloy NCs that Cu contents can be tuned from 10 % to 50 %, we further tuned the Cu portion from 50 % to 75 % by simply introducing n-butylamine in the reaction system. It is believed that n-butylamine plays a key role in breaking through a thermodynamic constraint in the formation of Pt-Cu alloy nanocrystals （NCs）. The synergistic effect of underpotential deposition-like Cu reduction and the different complexion abilities of amine group of n-butylamine with two metal species effectively tuned the reduction kinetics, by which each reduced Pt atom is able to catalyze reduction of more Cu atoms and be fully covered with 12 Cu atoms in the Pt-Cu alloy crystal, while Cu precursor is not able to be reduced solely and bind solely with Cu atoms, resulting in the successful tuning of Cu composition from 50 % to 75 %. In addition, we investigated the electro-catalytic activity of Pt-Cu bimetallic alloy NCs with different composition in electro-oxidation of methanol. The as-prepared PtCu3 NCs exhibit excellent electro-catalytic performance and stability in comparison with commercial Pt black and other compositional Pt-Cu alloy NCs.展开更多
基金supported by the National Basic Research Program of China(973 Program,2013CB933102)the National Natural Science Foundation of China(21273178,21573180,91545204)Xiamen-Zhuoyue Biomass Energy Co.Ltd~~
文摘Supported PtCu alloys have been broadly applied in heterogeneous catalysis and electrocatalysis owing to their excellent catalytic performance and high CO tolerance. It is important to analyze the outermost surface composition of the supported alloy nanoparticles to understand the nature of the catalytically active sites. In this paper, homogeneous face-centered cubic PtCu nanoparticles with a narrow particle size distribution were successfully fabricated and dispersed on a high-surface-area Ti〇2 powder support. The samples were oxidized and reduced in situ and then introduced into the ultrahigh vacuum chamber to measure the topmost surface composition by high-sensitivity low-energy ion scattering spectroscopy, and to determine the oxidation states of the elements by X-ray photoelectron spectroscopy. The surface composition and morphology, elemental distribu-tion, and oxidation states of the components were found to be significantly affected by the support and treatment conditions. The PtCu is de-alloyed upon oxidation with CuO wetting on the TiO2 sur-face and re-alloyed upon reduction. Phase diagrams of the surface composition and the bulk com-position were plotted and compared for the supported and unsupported materials.
文摘In this work,we have performed density functional theory(DFT)calculations to investigate the methanol electro‐oxidation reaction(MOR)catalyzed by the Pt,PtCu alloy and Cu.The complex reaction networks,including the intermediate dehydrogenation,water dissociation and anti‐poison reaction steps,are systematically investigated to explore the mechanisms.At the standard condition of pH=0 and zero potential,for Cu,most dehydrogenation steps along the favorable pathway are endergonic,making it less active in MOR.For the Pt and PtCu alloy,their dehydrogenation steps are mainly exergonic,but the formed CO intermediate binds too tightly on Pt,that can accumulate on active sites to poison the electro‐catalyst.The CO can be consumed by the thermodynamic reaction with OH*,which comes from water dissociation.DFT calculation shows alloying the Pt with Cu could not only reduce the free energy barrier for binding between CO*and OH*,but also assist the water dissociation to produce more OH*for that anti‐poison reaction.That makes the PtCu alloy more active than the pure Pt electrode in experiment.The results reveal the importance of anti‐poison reaction and water dissociation in MOR,which could be applied to the rational design of more active alloy electro‐catalysts in future.
基金supported by the National Basic Research Program of China(2011CBA00508 and 2015CB932301)the National Natural Science Foundation of China(21131005,21333008,and J1310024)the Natural Science Foundation of Fujian Province of China(2014J01058)
文摘In this paper, we reported a solvothermal method for the synthesis of octahedral Pt-Cu bimetallic alloy nanocrystals （NCs） with tunable composition. Inspired by the result from our previous exploration on octahedral Pt-Cu alloy NCs that Cu contents can be tuned from 10 % to 50 %, we further tuned the Cu portion from 50 % to 75 % by simply introducing n-butylamine in the reaction system. It is believed that n-butylamine plays a key role in breaking through a thermodynamic constraint in the formation of Pt-Cu alloy nanocrystals （NCs）. The synergistic effect of underpotential deposition-like Cu reduction and the different complexion abilities of amine group of n-butylamine with two metal species effectively tuned the reduction kinetics, by which each reduced Pt atom is able to catalyze reduction of more Cu atoms and be fully covered with 12 Cu atoms in the Pt-Cu alloy crystal, while Cu precursor is not able to be reduced solely and bind solely with Cu atoms, resulting in the successful tuning of Cu composition from 50 % to 75 %. In addition, we investigated the electro-catalytic activity of Pt-Cu bimetallic alloy NCs with different composition in electro-oxidation of methanol. The as-prepared PtCu3 NCs exhibit excellent electro-catalytic performance and stability in comparison with commercial Pt black and other compositional Pt-Cu alloy NCs.
