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TU Berlin

Inhalt des Dokuments

2012
Koteswara R. Vuyyuru, Peter Strasser

Oxidation of biomass derived 5-hydroxymethylfurfural using heterogeneous and electrochemical catalysis

Catalysis Today 195 (1), 144 - 154

DOI: 10.1016/j.cattod.2012.05.008

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The concept of biorefineries involves multiple catalytic processes to convert biomass feedstock into valuable chemical products. While conventional catalytic biomass-related processes are thermally activated, the catalytic activation of biomass conversion reactions using an electrical interfacial potential (electrocatalysis) is new and poorly explored to date. Here, we report a comparative study of biomass catalysis using thermal heterogeneous and electrocatalysis in liquid-phase. First, the oxidation of the biomass-derived model molecule 5-hydroxymethyl-2-furfural (HMF) was studied using aqueous-phase heterogeneous catalysis under mild temperature (50 °C) and pressure (10 bar O2) conditions. Oxidation reactions were carried out in a semi-batch reactor to test catalytic activity of Pt/C catalyst and compared with Au/TiO2, Ru/C, Rh/C and Pd/C. The important reaction parameters such as influence of pH, effect of pressure and type of catalytic metal surface were explored. HMF degradation at higher pH in the absence of metal catalyst was discussed using in situ NMR study. At lower pH (≤7), the alcoholic group of HMF oxidizes faster than aldehyde on Pt surface, whereas at higher pH (≤13), oxidation of alcoholic group appears as the rate-limiting step. At given reaction conditions, Au shows better catalytic activity than Pt, Pd, Ru and Rh at pH 13. The heterogeneously catalyzed oxidation of HMF was then compared to the corresponding electrochemical oxidation catalysis. Electrochemical catalysis offers an added advantage by providing the electrode potential and the faradaic current as two additional external control parameters. These are helpful to tune the thermodynamic driving force, activation energy and thus the reaction rate and selectivity of complex reaction processes. The electrochemical activation of water at anodic electrode potentials results in the in situ generation of reactive oxygenated surface species from the aqueous solvent and thus eliminates the use of molecular oxygen. The electrocatalytic oxidation of HMF was found very selective for the formation of 2,5-furandicarbaldehyde.
A.R. Zeradjanin, N. Menzel, P. Strasser, W. Schuhmann

Role of Water in the Chlorine Evolution at RuO2-Based Electrodes - Understanding Electrocatalysis as a Resonance Phenomenon

ChemSusChem 5 (10), 1897 - 1904

DOI: 10.1002/cssc.201200193

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The reaction path of the Cl2 evolution reaction (CER) was investigated by combining electrochemical and spectroscopic methods. It is shown that oxidation and reconstruction of the catalyst surface during CER is a consequence of the interaction between RuO2 and water. The state of the RuO2 surface during the electrochemical reaction was analyzed in situ by using Raman spectroscopy to monitor vibrations of the crystal lattice of RuO2 and changes in the surface concentration of the adsorbed species as a function of the electrode potential. The role of the solvent was recognized as being crucial in the formation of an oxygen-containing hydrophilic layer, which is a key prerequisite for electrocatalytic Cl2 formation. Water (more precisely the OH adlayer) is understood not just as a medium that allows adsorption of intermediates, but also as an integral part of the intermediate formed during the electrochemical reaction. New insights into the general understanding of electrocatalysis were obtained by utilizing the vibration frequencies of the crystal lattice as a dynamic catalytic descriptor instead of thermodynamic descriptors, such as the adsorption energy of intermediates. Interpretation of the derived "volcano" curve suggests that electrocatalysis is governed by a resonance phenomenon.
M. Heggen, M. Özaslan, L. Houben, P. Strasser

Formation and Analysis of Core-Shell Fine Structures in Pt Bimetallic Nanoparticle Fuel Cell Electrocatalysts

J. Phys. Chem. C 116 (36), 19073 - 19083

DOI: 10.1021/jp306426a

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An Ångstrom-scale structural and compositional investigation of a dealloyed Pt−Co core−shell nanoparticle fuel cell catalyst with characteristic diameter of 10−15 nm in an early stage of its life cycle reveals unusual selforganized compositional subsurface fine structure, that is, subsequent shells of Co depletion and enrichment. The origin of the unusual structure is rationalized by interplay of Co dissolution, Pt surface diffusion, and an inverse Kirkendall effect. A detailed picture about the chemical composition of the surface and subsurface provides a fundamental insight into the catalytically active structure of bimetallic electrocatalysts.
T. Reier, M. Özaslan, P. Strasser

Electrocatalytic Oxygen Evolution Reaction (OER) on Ru, Ir, and Pt catalysts: A Comparative Study of Nanoparticles and Bulk Materials

ACS Catalysis 2 (8), 1765 - 1772

DOI: 10.1021/cs3003098

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A comparative investigation was performed to examine the intrinsic catalytic activity and durability of carbon supported Ru, Ir, and Pt nanoparticles and corresponding bulk materials for the electrocatalytic oxygen evolution reaction (OER). The electrochemical surface characteristics of nanoparticles and bulk materials were studied by surface-sensitive cyclic voltammetry. Although basically similar voltammetric features were observed for nanoparticles and bulk materials of each metal, some differences were uncovered highlighting the changes in oxidation chemistry. On the basis of the electrochemical results, we demonstrated that Ru nanoparticles show lower passivation potentials compared to bulk Ru material. Ir nanoparticles completely lost their voltammetric metallic features during the voltage cycling, in contrast to the corresponding bulk material. Finally, Pt nanoparticles show an increased oxophilic nature compared to bulk Pt. With regard to the OER performance, the most pronounced effects of nanoscaling were identified for Ru and Pt catalysts. In particular, the Ru nanoparticles suffered from strong corrosion at applied OER potentials and were therefore unable to sustain the OER. The Pt nanoparticles exhibited a lower OER activity from the beginning on and were completely deactivated during the applied OER stability protocol, in contrast to the corresponding bulk Pt catalyst. We highlight that the OER activity and durability were comparable for Ir nanoparticles and bulk materials. Thus, Ir nanoparticles provide a high potential as nanoscaled OER catalyst.
J. Rossmeisl, P. Ferrin, G.A. Tritsaris, A.U. Nilekar, S. Koh, S.E. Bae, S.R. Brankovic, P. Strasser, M. Mavrikakis

Bifunctional anode catalysts for direct methanol fuel cells

Energy & Environmental Science 5 (8), 8335 - 8342 

DOI: 10.1039/c2ee21455e

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Using the binding energy of OH* and CO* on close-packed surfaces as reactivity descriptors, we screen bulk and surface alloy catalysts for methanol electro-oxidation activity. Using these two descriptors, we illustrate that a good methanol electro-oxidation catalyst must have three key properties: (1) the ability to activate methanol, (2) the ability to activate water, and (3) the ability to react off surface intermediates (such as CO* and OH*). Based on this analysis, an alloy catalyst made up of Cu and Pt should have a synergistic effect facilitating the activity towards methanol electro-oxidation. Using these two reactivity descriptors, a surface PtCu3 alloy is proposed to have the best catalytic properties of the Pt–Cu model catalysts tested, similar to those of a Pt–Ru bulk alloy. To validate the model, experiments on a Pt(111) surface modified with different amounts of Cu adatoms are performed. Adding Cu to a Pt(111) surface increases the methanol oxidation current by more than a factor of three, supporting our theoretical predictions for improved electrocatalysts.
C. Yu, E.F. Holby, R. Yang, M.F. Toney, D. Morgan, P. Strasser

Growth Trajectories and Coarsening Mechanisms of Metal Nanoparticle Electrocatalysts

ChemCatChem 4 (6), 766 - 770

DOI: 10.1002/cctc.201200090

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In situ small angle X-ray scattering (SAXS) combined with an electrochemical rate model yield insight in the evolution of the particle size distributions (PSDs) of carbon-supported Pt nanoparticle ensembles. A critical 3–5 nm size region where particles remained structurally stable was identified. A dominant role for a surface energy-driven Ostwald growth mechanism was deduced.
K. Mette, A. Bergmann, J.-P. Tessonnier, M. Havecker, L. Yao, T. Ressler, R. Schlögl, P. Strasser, M. Behrens

Nanostructured Manganese Oxide Supported on Carbon Nanotubes for Electrocatalytic Water Splitting

ChemCatChem 4 (6), 851 - 862

DOI: 101002/cctc.201100434

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Incipient wetness impregnation and a novel deposition symproportionation precipitation were used for the preparation of MnOx/CNT electrocatalysts for efficient water splitting. Nanostructured manganese oxides have been dispersed on commercial carbon nanotubes as a result of both preparation methods. A strong influence of the preparation history on the electrocatalytic performance was observed. The as-prepared state of a 6.5 wt. % MnOx/CNT sample could be comprehensively characterized by comparison to an unsupported MnOx reference sample. Various characterization techniques revealed distinct differences in the oxidation state of the Mn centers in the as-prepared samples as a result of the two different preparation methods. As expected, the oxidation state is higher and near +4 for the symproportionated MnOx compared to the impregnated sample, where +2 was found. In both cases an easy adjustability of the oxidation state of Mn by post-treatment of the catalysts was observed as a function of oxygen partial pressure and temperature. Similar adjustments of the oxidation state are also expected to happen under water splitting conditions. In particular, the 5 wt. % MnO/CNT sample obtained by conventional impregnation was identified as a promising catalytic anode material for water electrolysis at neutral pH showing high activity and stability. Importantly, this catalytic material is comparable to state-of-art MnOx catalyst operating in strongly alkaline solutions and, therefore, offers advantages for hydrogen production from waste and sea water under neutral, hence, environmentally benign conditions.
B. Eckhardt, E. Ortel, J. Polte, D. Bernsmeier, O. Görke, P. Strasser, R. Kraehnert

Micelle-templated Mesoporous Films of Magnesium Carbonate and Magnesium Oxide

Advanced Materials 24 (23), 3115 – 3119

DOI: 10.1002/adma.201104984

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Ordered mesoporous MgO films are synthesized via micelle-templating for the first time. The problems of low melting points, insolubility and excessive crystallization of the metal oxide precursors are overcome by synthesizing in-situ a magnesium nitrate-citric acid complex. The stepwise thermal transformation into magnesium carbonate and then MgO was studied as well as the evolution of the mesopore structure.
L. Gan, M. Heggen, S. Rudi, P. Strasser

Core−Shell Compositional Fine Structures of Dealloyed PtxNi1−x Nanoparticles and Their Impact on Oxygen Reduction Catalysis

Nano Lett. 12 (10), 5423 - 5430

DOI: 10.1021/nl302995z

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Using aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy line profiles with Ångstrom resolution, we uncover novel core–shell fine structures in a series of catalytically active dealloyed PtxNi1–x core–shell nanoparticles, showing the formation of unusual near-surface Ni-enriched inner shells. The radial location and the composition of the Ni-enriched inner shells were sensitively dependent on the initial alloy compositions. We further discuss how these self-organized Ni-enriched inner shells play a key role in maintaining surface lattice strain and thus control the surface catalytic activity for oxygen reduction.
C. Cui, L. Gan, H.-H. Li, S.-H. Yu, M. Heggen, P. Strasser

Octahedral PtNi Nanoparticle Catalysts: Exceptional Oxygen Reduction Activity by Tuning the Alloy Particle Surface Composition

Nano Lett. 12 (11), 5885 - 5889

DOI: 10.1021/nl3032795

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We demonstrate how shape selectivity and optimized surface composition result in exceptional oxygen reduction activity of octahedral PtNi nanoparticles (NPs). The alloy octahedra were obtained by utilizing a facile, completely surfactant-free solvothermal synthesis. We show that the choice of precursor ligands controls the shape, while the reaction time tunes the surface Pt:Ni composition. The 9.5 nm sized PtNi octahedra reached a 10-fold surface area-specific (∼3.14 mA/cmPt2) as well as an unprecedented 10-fold Pt mass based (∼1.45 A/mgPt) activity gain over the state-of-art Pt electrocatalyst, approaching the theoretically predicted limits.
A. Marcu, G. Toth, R. Srivastava, P. Strasser

Preparation, characterization and degradation mechanisms of PtCu alloy nanoparticles for automotive fuel cells

Journal Power Sources 208, 288 - 295

DOI: 10.1016/j.jpowsour.2012.02.065

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Electrochemically dealloyed PtCu alloy nanoparticles successfully meet the automotive technology target of having four times higher Pt mass activity for the electroreduction of molecular oxygen compared to current state-of-the-art platinum catalysts. However, the catalysts must also maintain their activity throughout the aggressive automotive drive-cycles in order to be implemented in fuel cells cars. Here, the durability of dealloyed PtCu catalysts was systematically evaluated under various voltage-cycles using a rotating ring disk electrode. The stability of the non-noble metal alloy component was proven at electrode potentials below 0.6 V. The platinum stability was evaluated at potentials up to 1.1 V to avoid carbon corrosion and then up to 1.2 V to be closer to the more aggressive cycles developed in startup/shutdown events of the fuel cells. The major known failure modes such as non-noble metal dissolution, platinum dissolution, and particle growth/agglomeration were monitored in order to understand closely the PtCu nanoparticles behavior under different potential cycles and to provide a degradation fingerprint.
F. Hasché, T.-P. Fellinger, M. Oezaslan, J.P. Paraknowitsch, M. Antonietti, P. Strasser

Mesoporous Nitrogen Doped Carbon Supported Platinum PEM Fuel Cell Electrocatalyst Made From Ionic Liquids

ChemCatChem 4 (4), 479 - 483 

DOI: 10.1002/cctc.201100408

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An ionic liquid based mesoporous nitrogen doped carbon supported Pt nanoparticle fuel cell electrocatalyst (Pt/meso-BMP) as a new material class was synthesized and examined for the oxygen reduction reaction (ORR). The structural and electrochemical characterization of this new material class shows a high electrochemical active surface area (ECSA) and the suitability for the ORR.
N. Menzel, E. Ortel, R. Kraehnert, P. Strasser

Electrocatalysis Using Porous Nanostructured Materials

ChemPhysChem 13 (6), 1385  -1394

DOI: 10.1002/cphc.201100984

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The performance of electrochemical reactions depends strongly on the morphology and structure of the employed catalytic electrodes. Nanostructuring of the electrode surface represents a powerful tool to increase the electrochemically active surface area of the electrodes. Moreover, it can also facilitate faster diffusive mass transport inside three-dimensional electrodes. This minireview describes recent trends in the development of synthesis routes for porous nanostructured electrode materials and discusses the respective important electrocatalytic applications. The use of structure-directing agents will play a decisive role in the design and synthesis of improved catalysts.
F. Hasché, M. Oezaslan, P. Strasser

In Situ Observation of the Thermally Induced Growth of Platinum-Nanoparticle Catalysts Using High-Temperature X-ray Diffraction

ChemPhysChem 13 (3), 828 - 834

DOI: 10.1002/cphc.201100857

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Fundamental understanding about the thermal stability of nanoparticles and deliberate control of structural and morphological changes under reactive conditions is of general importance for a wide range of reaction processes in heterogeneous and electrochemical catalysis. Herein, we present a parametric study of the thermal stability of carbon-supported Pt nanoparticles at 80 °C and 160 °C, with an initial particle size below 3 nm, using in situ high-temperature X-ray diffraction (HT-XRD). The effects on the thermal stability of carbon-supported Pt nanoparticles are investigated with control parameters such as Brunauer–Emmet–Teller (BET) surface area, metal loading, temperature, and gas environment. We demonstrate that the growth rate exhibits a complex, nonlinear behavior and is largely controlled by the temperature, the initial particle size, and the interparticle distance. In addition, an ex situ transmission electron microscopy study was performed to verify our results obtained from the in situ HT-XRD study.
T.-P. Fellinger, F. Hasché, P. Strasser, M. Antonietti

Mesoporous Nitrogen-Doped Carbon for the Electrocatalytic Synthesis of Hydrogen Peroxide

J. Am. Chem. Soc. 134 (9), 4072  - 4075

DOI: 10.1021/ja300038p

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Mesoporous nitrogen-doped carbon derived from the ionic liquid N-butyl-3-methylpyridinium dicyanamide is a highly active, cheap, and selective metal-free catalyst for the electrochemical synthesis of hydrogen peroxide that has the potential for use in a safe, sustainable, and cheap flow-reactor-based method for H2O2 production.
P. Mathew, J.P. Meyers, R. Srivastava, P. Strasser

Analysis of Surface Oxidation on Pt and Pt Core-Shell Electrocatalysts for PEFCs

J. Electrochem. Soc. 159 (5), B1 - B10

doi: 10.1149/2.066205jes

Studies on the formation and reduction of surface oxide on Pt-Cu/C core-shell electrocatalysts have been carried out with reference to the nature and type of the adsorbed intermediates formed on the surface as a function of applied potential. In-situ measurements were made using EQCM coupled with cyclic voltammetry to monitor the surface changes. Comparisons between the novel “core-shell” electrocatalysts, conventional Pt/C electrocatalysts and unsupported Pt black electrocatalysts have been made. We find that interfacial mass of the adsorbed species increases in a continuous linear manner as the potential is increased during the anodic oxidation. We also find evidence to suggest that the oxide formation on the core-shell electrocatalyst occurs via the formation of adsorbed hydroxyl species involving one electron per surface site and that on pure Pt proceeds via adsorbed oxide involving two electrons per site. A different mechanism for oxide growth on these catalysts was confirmed by the change in the Tafel slopes for anodic oxidation of the surface. The results showed that the core-shell catalyst surface is less oxidized and that the surface strain imposes a barrier to surface oxidation. This also explains the shift in the oxide stripping peak that has been observed for the Pt binary alloy catalysts.
M. Oezaslan, M. Heggen, P. Strasser

Size-dependent morphology of dealloyed bimetallic catalysts: Linking the nano to the macro scale

J. Am. Chem. Soc. 134, 514 - 524

DOI: 10.1021/ja2088162

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Chemical dealloying of Pt binary alloy precursors has emerged as a novel and important preparation process for highly active fuel cell catalysts. Dealloying is a selective (electro)chemical leaching of a less noble metal M from a M rich Pt alloy precursor material and has been a familiar subject of macroscale corrosion technology for decades. The atomic processes occurring during the dealloying of nanoscale materials, however, are virtually unexplored and hence poorly understood. Here, we have investigated how the morphology and intraparticle composition depend on the particle size of dealloyed Pt–Co and Pt–Cu alloy nanoparticle precursor catalysts. To examine the size–morphology–composition relation, we used a combination of high-resolutionscanning transmission electron microscopy (STEM), transmission electron microscopy (TEM), electron energy loss (EEL) spectroscopy, energy-dispersive X-ray spectroscopy (EDS), and surface-sensitive cycling voltammetry. Our results indicate the existence of three distinctly different size-dependent morphology regimes in dealloyed Pt–Co and Pt–Cu particle ensembles: (i) The arrangement of Pt shell surrounding a single alloy core (“single core–shell nanoparticles”) is exclusively formed by dealloying of particles below a characteristic diameter dmultiple cores of 10–15 nm. (ii) Above dmultiple cores, nonporous bimetallic core–shell particles dominate and show structures with irregular shaped multiple Co/Cu rich cores (“multiple cores–shell nanoparticles”). (iii) Above the second characteristic diameter dpores of about 30 nm, the dealloyed Pt–Co and Pt–Cu particles start to show surface pits and nanoscale pores next to multiple Co/Cu rich cores. This structure prevails up to macroscopic bulklike dealloyed particles with diameter of more than 100 nm. The size–morphology–composition relationships link the nano to the macro scale and provide an insight into the existing material gap of dealloyed nanoparticles and highly porous bulklike bimetallic particles in corrosion science.
X. Tuaev, J. P. Paraknowitsch, R. Illgen, A. Thomas, P. Strasser

Nitrogen-doped coatings on carbon nanotubes and their stabilizing effect on Pt nanoparticles

Phys. Chem. Chem. Phys. 14 (18), 6444 - 6447

DOI: 10.1039/c2cp40760d

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A homogeneous coating of nitrogen-doped carbon on carbon nanotubes is performed using ionic liquids. The N-doped material is employed as a support for nanoparticles. Electrochemical degradation behavior is monitored in situ and compared to an unmodified material. The strongly enhanced stability is explained on the basis of a Pt–nitrogen interaction.
F. Hasché, M. Oezaslan, P. Strasser

Activity, Structure, and Degradation of Dealloyed PtNi3 Nanoparticle Electrocatalyst for the Oxygen Reduction Reaction in PEMFC

J. Electrochem. Soc. 159 (1), B25 - B29

DOI: 10.1149/2.030201jes

We report a synthesis, activity and stability study of a dealloyed, highly active PtNi3 alloy nanoparticle catalyst for the oxygen reduction reaction (ORR) in acidic media. After activation by electrochemical dealloying of a PtNi3 precursor, the Pt-Ni nanoparticle catalyst (referred to as “dealloyed PtNi3”) exhibits a 7–8 times higher Pt mass based activity and a 6–7 times higher Pt surface area specific based activity for ORR than pure Pt at comparable mean particle size. In addition, the long-term stability of the dealloyed PtNi3 was tested for typical fuel cell operating as well as more corrosive fuel cell start-up conditions. After 10000 voltage cycles between 0.5–1.0 V vs. RHE at 50 mV s−1 the dealloyed PtNi3 catalyst still shows 4–5 fold increase in Pt surface area specific based activity compared with that for pure Pt.
M. Oezaslan, F. Hasché, P. Strasser

Oxygen Electroreduction on PtCo3, PtCo and Pt3Co Alloy Nanoparticles for Alkaline and Acidic PEM Fuel Cells

J. Electrochem. Soc. 159 (4), B394 - B405

DOI: 10.1149/2.075204jes

Pt-Co alloy nanoparticles have emerged as one of the most promising electrocatalysts for the oxygen reduction reaction (ORR) in hydrogen fuel cells. Our study presents a comprehensive structural, compositional and electrochemical characterization linked with ORR activity for carbon supported PtCo3, PtCo, and Pt3Co alloy nanoparticle catalysts in 0.1 M HClO4 and 0.1 M KOH. Surface-sensitive cyclic voltammetry was used to investigate the changes of composition of outermost atomic layers of Pt-Co alloys. Our electrochemical results in alkaline media clearly show the stability and voltage-induced accumulation of Co on the particle surface, whereas in 0.1 M HClO4 the voltage cycling initiates the rapid dissolution of Co to form a Pt-enriched surface surrounding by alloy core. We correlated the ECSA and ORR activity with the as-synthesized chemical composition of Pt-Co alloys. In results, after electrochemical treatment in 0.1 M HClO4 the Pt mass based activities (jmass) increase according: Pt(HT) < PtCo < Pt3Co < PtCo3 at comparable particle size. Unlike to acid, after voltage cycling in 0.1 M KOH jmass increase according: PtCo3 < Pt(HT) < PtCo < Pt3Co. However, in 0.1 M KOH activated PtCo3 core-shell catalyst shows 4–5 fold higher mass activity compared to pure Pt and Pt(HT).
M. Oezaslan, F. Hasché, P. Strasser

PtCu3, PtCu and Pt3Cu Alloy Nanoparticle Electrocatalysts for Oxygen Reduction Reaction in Alkaline and Acidic Media

J. Electrochem. Soc. 159 (4), B444 - B454

DOI: 10.1149/2.106204jes

Dealloying of Pt bimetallic nanoparticles is a promising synthesis method to prepare highly active electrocatalysts for oxygen reduction reaction (ORR) in alkaline and acidic PEM fuel cells. We present here a structural, compositional and electrochemical characterization linked with ORR activity for carbon supported PtCu3, PtCu, and Pt3Cu alloy nanoparticles in different electrolytes and pH values. The effects of electrolyte and pH are systematically examined on the ECSA and Pt mass based activity (jmass) for various Pt-Cu alloys. We observed the formation of Cu oxide species and redissolution/redeposition of Cu species during the voltage cycling up to 1.0 V/RHE in 0.1 M KOH. In contrast, the voltage cycling in 0.1 M HClO4 immediately causes the dissolution of Cu and results in Pt-enriched particle surface. We have correlated the ECSA and mass activity with the as-synthesized composition in dependence on both electrolytes. In summary, after voltage cycling in 0.1 M HClO4 the values of jmass increase according: Pt3Cu < PtCu < PtCu3. However, after voltage cycling in 0.1 M KOH the values of jmass increase in the following trend: PtCu3 < PtCu < Pt3Cu. Only after activation process, PtCu3 core-shell catalyst shows significantly enhanced ORR activity in 0.1 M KOH compared to pure Pt.
L. Borchardt, F. Hasché, M. Oschatz, F. Schmidt, E. Kockrick, Ch. Ziegler, T. Lescouet, A. Bachmatiuk, B. Buechner, D. Farrusseng, P. Strasser, S. Kaskel

Transition metal loaded silicon carbide-derived carbons with enhanced catalytic properties

Carbon 50 (5), 1861 - 1870

DOI: 10.1016/j.carbon.2011.12.036

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Carbide-derived carbons (CDC) with incorporated transition metal nanoparticles (∼2.5 nm) were prepared using a microemulsion approach. Time-consuming post synthesis functionalization of the carbon support material can thus be avoided and nanoparticle sizes can be controlled by changing the microemulsion composition. This synthesis strategy is a technique for the preparation of highly porous carbon materials with a catalytically active component. In particular we investigated the integration of ruthenium, palladium, and platinum in a concentration ranging from 4.45 to 12 wt.%. It was found that the transition metal has a considerable influence on sorption properties of resulting nanoparticle-CDC composite materials. Depending on the used metal salt additive the surface area and the pore volume ranges from 1480 m2/g and 1.25 cm3/g for Pt to 2480 m2/g and 2.0 cm3/g for Ru doped carbons. Moreover, members of this material class show impressive properties as heterogeneous catalysts. The liquid phase oxidation of tetralin and the partial oxidation of methane were studied, and electrochemical applications were also investigated. Primarily Pt doped CDCs are highly active in the oxygen reduction reaction, which is of great importance in present day fuel cell research.

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