Pt-Mo Catalysts Research Articles

Awakening (220) as One More Active Facet of PtMo Alloy via Single‐Atom Doping to Boost Ammonia Electrooxidation in Direct Ammonia Fuel Cell

AbstractAs the core of low‐temperature direct ammonia fuel cell (DAFC) technology, electrocatalytic ammonia oxidation reaction (AOR) has proven to be most active on platinum‐based catalysts. However, the AOR is extremely surface sensitive that only the Pt (200) facet exhibits high reaction activity, whereas other facets usually do not make contributions. Herein, the inert (220) surface of PtMo nano‐alloy is successfully awakened as one more active facet in addition to (200) via directional single‐atom Ni‐doping. The introduction of Ni triggers a targeted electron accumulation around Pt sites at the (220) facet that significantly reduces the AOR energy barrier while maintaining the activity of the (200) surface. With a greatly enlarged active surface, the Ni‐decorated PtMo catalyst exhibits a significantly facilitated AOR kinetics with a low onset potential of 0.49 V versus reversible hydrogen electrode and a superior peak current density of 94.96 A g−1 at 5 mV s−1. Notably, the DAFC equipped with such an electrocatalyst reaches a remarkable peak power density of 16.70 mW cm−2 at low temperatures. It is believed that this strategy sheds light on exploiting the intrinsic activity of Pt‐based electrocatalysts, and drives the low‐temperature DAFC technology to a more practical level.

EIS and relaxation times study for CO adsorbed on bimetallic Pt-Mo catalysts during the methanol oxidation reaction

Both Pt/C and PtMo/C catalysts were synthesized by Platinum and Molybdenum phases with Vulcan Carbon as support. The behavior of Pt-based catalysts in electrolytic media was analyzed and its Electrochemical Impedance Spectroscopy (EIS) was fitted as electric circuits to elucidate mechanisms such as adsorption, desorption and oxidation that developed during the methanol oxidation reaction through Direct Methanol Fuel Cells (DMFC). Special attention was paid to the carbon monoxide oxidation reaction on the catalyst surfaces to detect the CO poisoning effect. EIS data were used to propose the modified Randles electric circuits, which consisted of a Constant Phase Element (CPE) connected in parallel with the series of Charge Transfer Resistance (RCT) and a Finite Diffusion Warburg Element (ZW), aimed at identifying the mass transfer process. Distribution of Relaxation Times analysis (DRT) was estimated to identify other characteristics of the individual processes for both catalysts and to detect the poisoning effect of the species adsorbed on the catalyst surface.

Ruling Factors in Cinnamaldehyde Hydrogenation: Activity and Selectivity of Pt-Mo Catalysts.

To obtain selective hydrogenation catalysts with low noble metal content, two carbon-supported Mo-Pt bimetallic catalysts have been synthesized from two different molybdenum precursors, i.e., Na2MoO4 and (NH4)6Mo7O24. The results obtained by X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) combined with the presence and strength of acid sites clarified the different catalytic behavior toward cinnamaldehyde hydrogenation. After impregnating the carbon support with Mo precursors, each sample was used either as is or treated at 400 °C in N2 flow, as support for Pt nanoparticles (NPs). The heating treatment before Pt deposition had a positive effect on the catalytic performance. Indeed, TEM analyses showed very homogeneously dispersed Pt NPs only when they were deposited on the heat-treated Mo/C supports, and XPS analyses revealed an increase in both the exposure and reduction of Pt, which was probably tuned by different MoO3/MoO2 ratios. Moreover, the different acid properties of the catalysts resulted in different selectivity.

Selective Catalytic Reduction of NOx by CO over Doubly Promoted MeMo/Nb2O5 Catalysts (Me = Pt, Ni, or Co)

Doubly promoted MeMo/Nb2O5 catalysts, in which Me = Pt, Ni, or Co oxides were prepared for the selective catalytic reduction of NOx by CO reaction (CO-SCR). Comparable chemical, textural, and structural analyses revealed similarities between NiMo and CoMo impregnated on Nb2O5, in contrast to PtMo sites, which were not homogeneously dispersed on the support surface. Both the acid function and metal dispersion gave a synergistic effect for CO-SCR at moderate temperatures. The reactivity of PtMo catalysts towards NOx and CO chemisorption was at low reaction temperatures, whereas the NOx conversion over CoMo was greatly improved at relatively high temperatures. Careful XPS, NH3-TPD, and HRTEM analyses confirmed that the large amounts of strong and moderate acid sites from PtOx entrapped on MoO3 sites induced high NOx conversions. NiMo/Nb2O5 showed poor performance in all conditions. Poisoning of the MeMo sites with water vapor or SO2 (or both) provoked the decline of the NOx conversions over NiMo and PtMo sites, whereas the structure of CoMo ones remained very active with a maximum NOx conversion of 70% at 350 °C for 24 h of reaction. This was due to the interaction of the Co3+/Co2+ and Mo6+ actives sites and the weak strength Lewis acid Nb5+ ones, as well.

Catalytic Platinum Nanoparticles Decorated with Subnanometer Molybdenum Clusters for Biomass Processing.

The development of improved technologies for biomass processing into transportation fuels and industrial chemicals is hindered due to a lack of efficient catalysts for selective oxygen removal. Here we report that platinum nanoparticles decorated with subnanometer molybdenum clusters can efficiently catalyze hydrodeoxygenation of acetic acid, which serves as a model biomass compound. In contrast with monometallic Mo catalysts that are inactive and monometallic Pt catalysts that have low activities and selectivities, bimetallic Pt-Mo catalysts exhibit synergistic effects with high activities and selectivities. The maximum activity occurs at a Pt to Mo molar ratio of three. Although Mo atoms themselves are catalytically inactive, they serve as preferential binding anchors for oxygen atoms while a catalytic transformation proceeds on neighboring surface Pt atoms. Beyond biomass processing, Pt-Mo nanoparticles are promising catalysts for a wide variety of reactions that require a transformation of molecules with an oxygen atom and, more broadly, in other fields of science and technology that require tuning of surface-oxygen interactions.

Intrinsic activity of interfacial sites for Pt-Fe and Pt-Mo catalysts in the hydrogenation of carbonyl groups

Bimetallic PtFe/SiO2 and PtMo/SiO2 catalysts were prepared using controlled surface reactions (CSR) of (cyclohexadiene)iron tricarbonyl and (cycloheptatriene)molybdenum tricarbonyl on a Pt/SiO2 parent material. These catalysts were studied for the hydrogenation of ketone and aldehyde groups. Selective deposition of Fe onto Pt nanoparticles via the CSR method was confirmed by UV–vis absorption spectroscopy, scanning transmission electron microscopy, and inductively coupled plasma absorption emission spectroscopy. The oxidation states of the Pt and Fe species for PtFe catalysts were determined following treatment in H2 at 573 K using X-ray photoelectron spectroscopy, showing that the dominant Pt phase is metallic Pt, while Fe is present in the metallic and +2 oxidation states, and Mo is present as a mixture of metallic, +4, and +6 oxidation states. The turnover frequency (TOF) of a Pt site for acetone (ketone) hydrogenation at 353 K and atmospheric pressure is 0.9 min−1, whereas the TOF values of Pt-FexOy and Pt-MoOx sites are 93 and 76 min−1, respectively. For the hydrogenation of 2-hydroxytetrahydropyran (2-HY-THP, aldehyde) at 393 K and 30 bar pressure, the TOF of a Pt site is 7.8 min−1, while the TOF values of Pt-FexOy and Pt-MoOx sites are 480 and 830 min−1, respectively. The order of magnitude enhancement of the TOF on the Pt-FexOy and Pt-MoOx interfacial sites compared to that of the Pt site suggests that the Pt-metal oxide interface created on Pt catalysts by selective addition of Fe and Mo are active sites for both acetone and 2-HY-THP hydrogenation reactions. The presence of interfacial sites may enhance the catalytic activity over PtFe/SiO2 and PtMo/SiO2 catalysts by stabilization of adsorbed reactive intermediates through bonding with CO groups.

Surface Chemistry of Aromatic Reactants on Pt- and Mo-Modified Pt Catalysts

Supported catalysts containing an oxophilic metal such as Mo and a noble metal such as Pt have shown promising activity and selectivity for deoxygenation of biomass-derived compounds. Here, we report that PtMo catalysts also promote hydrogenolysis of the model compound benzyl alcohol, while decarbonylation is most prevalent over unmodified Pt. A combination of single crystal surface science studies, density functional theory (DFT) calculations, and vapor phase upgrading experiments using supported catalysts was carried out to better understand the mechanism by which Mo promotes deoxygenation. Molybdenum was deposited in submonolayer quantities on a Pt(111) surface and reduced at high temperature. Temperature-programmed desorption (TPD) experiments using benzyl alcohol as a reactant showed greatly enhanced yields of the deoxygenation product toluene at moderate Mo coverages. To understand how the interaction of the aromatic group with the surface influenced this reactivity, we investigated the adsorption o...

Measurement of intrinsic catalytic activity of Pt monometallic and Pt-MoOx interfacial sites over visible light enhanced PtMoOx/SiO2 catalyst in reverse water gas shift reaction

Supported Pt-Mo catalysts were prepared with different Mo contents by a controlled surface reaction (CSR) method and studied for the reverse water gas shift (RWGS) reaction under dark and visible light irradiation conditions. Characterization results from Raman spectroscopy, scanning transmission electron microscopy (STEM), CO chemisorption, and inductively coupled plasma-absorption emission spectroscopy (ICP-AES) indicate that selective Mo deposition onto Pt was achieved at low Mo loading (Mo/Pt ratio<0.3). Mo deposition changed the apparent activation energy and CO2 and CO reaction orders. Visible light irradiation changed the apparent activation energy and reaction orders of CO2, CO, and H2, ascribed to direct photoexcitation. The intrinsic activity of a Pt site is 0.4 and 4.1min−1 under dark and light conditions at 473K, respectively, whereas the intrinsic activity of a Pt-MoOx site is increased to 22.7 and 160min−1 under dark and light conditions at 473K, respectively.

Enhanced Hydrodeoxygenation of m-Cresol over Bimetallic Pt–Mo Catalysts through an Oxophilic Metal-Induced Tautomerization Pathway

Supported bimetallic catalysts consisting of a noble metal (e.g., Pt) and an oxophilic metal (e.g., Mo) have received considerable attention for the hydrodeoxygenation of oxygenated aromatic compounds produced from biomass fast pyrolysis. Here, we report that PtMo can catalyze m-cresol deoxygenation via a pathway involving an initial tautomerization step. In contrast, the dominant mechanism on monometallic Pt/Al2O3 was found to be sequential Pt-catalyzed ring hydrogenation followed by dehydration on the support. Bimetallic Pt10Mo1 and Pt1Mo1 catalysts were found to produce the completely hydrogenated and deoxygenated product, methylcyclohexane (MCH), with much higher yields than monometallic Pt catalysts with comparable metal loadings and surface areas. Over an inert carbon support, MCH formation was found to be slow over monometallic Pt catalysts, while deoxygenation was significant for PtMo catalysts even in the absence of an acidic support material. Experimental studies of m-cresol deoxygenation togeth...

Dehydrogenation of methylcyclohexane to toluene over partially reduced silica-supported Pt-Mo catalysts

A series of bifunctional Pt/Mo(x)-SiO2 catalysts were investigated in the context of the hydrogen storage using the methylcyclohexane (MCH)-toluene-hydrogen cycle. The performance of partially reduced catalysts for hydrogen production was evaluated in the MCH dehydrogenation reaction carried out in a fixed-bed flow reactor at 673K and total hydrogen pressure of 2.2MPa. The catalysts with different acidity and Mo loading (4.1–12.7wt.%) were prepared by impregnation of the calcined Mo(x)-SiO2 samples with Pt precursor. The oxide catalyst precursors were characterized by chemical analysis (ICP-AES), N2 physisorption at 77K, X-ray diffraction (XRD), Raman spectroscopy and temperature-programmed reduction (H2-TPR) techniques whereas the partially reduced samples were characterized by temperature-programmed adsorption of ammonia (TPD-NH3), high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). The catalyst having optimized Mo loading (8.0wt.%) was the most active and its best catalytic performance was attributed to the high dispersion of MoO2 and Pt° phases and its lowest deactivation by coke formation. The activity drop of the catalysts having larger Mo loading (10.6 and 12.7wt.%) was linked with formation of MoOx-Pt core-shell nanoparticles, as confirmed by HRTEM.

Pt Surfaces Modified with Mo Species as an Improved Electrocatalyst for Efficient Water Splitting

Increasing energy demand along with the environmental concerns associated with our absolute dependence on fossil fuels has attracted huge research efforts to utilize renewable energy. Using solar energy, the photocatalytic water splitting reaction represents one of the most efficient systems to produce stoichiometric amounts of hydrogen (and oxygen) without any carbon footprint.[1] The cocatalyst role in the water splitting reaction is of paramount importance. Noble metals (Pt, Rh, Pd, Ru, etc.) are efficient electrocatalysts to reduce protons/water and form hydrogen gas (hydrogen evolution reaction, HER). Pt is also the most common used cocatalyst in the photocatalytic field.[2] However, it is well known that Pt is highly active on the oxygen reduction reaction (ORR), which can be described in a photocatalytic system as the reaction of water formation (back reaction of the water electrolysis).[3] If Rh cocatalyst was loaded in the surface of an advanced photocatalytic systems such as (Ga1−x Zn x )(N1−x O x ) stable production of hydrogen and oxygen gases were not detected. Only when a thin layer of Cr oxide was present around the hydrogen evolution site overall water splitting was achieved.[4] Based on electrochemical studies of model electrodes, it was suggested that the oxide layer selectively permeates protons and hydrogen molecules but not oxygen molecules, thus suppressing the back reaction catalyzed by noble metals (selective HER without introducing ORR).[5] To understand the redox chemistry at the cocatalyst interface, electrochemical methods were utilized to model the electrocatalytic reactions present at the surface of photocatalysts. Particularly, a model platinum-disk electrode and homogeneously dispersed Pt nanoparticles on carbon black (Pt/C) were electrochemically coated with Mo materials. A systematic investigation by varying the loading of Mo was performed on the electrocatalytic activity for HER as well as for ORR. The Mo species were characterized by XPS, FT-IR, in-situ UV-Vis electrochemical spectroscopy and Raman spectroscopy. Electro-kinetic studies, cyclic voltammetry analysis and hydrodynamic techniques were used. When Mo species were electrodeposited in the Pt surfaces with a Mo:Pt ratio of 400:1 (estimated from electrodeposition charges), the Mo-modified Pt exhibited HER activity but inhibited ORR activity. Interestingly, the presence of Mo produces an almost insensitive surface towards ORR. The results indicate that the O2 adsorption step may be the rate-determining step estimated via the Koutecky-Levich equation and Tafel analysis. Moreover, hydrogen oxidation reaction (HOR) was hindered under the explored conditions and no diffusion effects were observed for the Pt-Mo catalysts. It appears to exist an optimum value of electrodeposited Mo species in which the creation of a selective catalyst was achieved. When the Mo/Pt ratio is less than 400 the active sites follow the Pt electrode behaviour with high activity for HER and ORR; yet when the ratio was larger than 400 both HER and ORR were completely inhibited. The possible mechanisms responsible of the selectivity towards HER and ORR are discussed based on the nature of the active sites associated with the Pt-Mo synergetic effect. The stability of the Mo materials was improved in the order alkaline < neutral < acidic conditions. This study provides an insight into the design of future cocatalysts required to drive overall water splitting in a single photocatalyst surface and the challenges ahead for future water splitting systems [1] K. Takanabe, K. Domen, Green, 2011, 1, 313. [2] K. Takanabe, K. Domen, ChemCatChem 2012, 4, 1485. [3] A. T. Garcia-Esparza, D. Cha, Y. Ou, J. Kubota, K. Domen, K. Takanabe, ChemSusChem 2013, 6, 168. [4] K. Maeda, K. Teramura, D. Lu, T. Takata, N. Saito, Y. Inoue and K. Domen, Nature 2006, 440, 295. [5] M. Yoshida, K. Takanabe, K. Maeda, A. Ishikawa, J. Kubota, Y. Sakata, Y. Ikezawa, K. Domen, J. Phys. Chem. C, 2009, 113 10151.

Structural and catalytic differences in the effect of Co and Mo as promoters for Pt-based aqueous phase reforming catalysts

Reaction rates (site time yields, normalized to CO chemisorption sites) and product selectivity were determined for PtCo, PtMo, and Pt supported on multi-walled carbon nanotubes for aqueous phase reforming of glycerol. The bimetallic PtCo and PtMo catalysts had 4.6× and 5.4× higher glycerol consumption rates than Pt, and 3.9× and 0.6× rates in H2 formation compared to Pt. Hydrogen generation selectivity was similar on Pt and PtCo, but PtMo had an increase in selectivity to CO cleavage products, which reduced H2 yield at conversions over 60% (85–90% hydrogen yield for Pt and PtCo, 65% for PtMo). X-ray absorption spectroscopy and scanning transmission electron microscopy results indicate that PtCo adopts multiple mono- and bimetallic structures (Pt shell/Co core, well-mixed alloy, Pt only), which maintain surface Pt sites that are selective to hydrogen generation while adding a promotional metal that increases reaction rates. This is in contrast to a previously characterized PtMo catalyst which introduced surface sites capable of deoxygenation reactions (in the form of PtMo metallic or PtMoO/OH acid pairs) which result in the observed decrease in selectivity.

Effect of support composition on the activity of Pt and PtMo catalysts in the conversion of n-hexadecane

The SiO2Al2O3 material and mesoporous molecular sieves of AlSBA-15 type described in this work were applied as the supports for the Pt and PtMo catalysts. Catalysts were synthesized by one step impregnation, i.e. Pt catalysts with 1wt.% of Pt as well as by two step impregnation, i.e. PtMo catalysts with 4–8wt.% of Mo followed by 1wt.% of Pt. The activity of the catalysts was investigated in n-C16 conversion (5MPa; 320–370°C; WSHV, 3.5h−1; H2:CH, 350:1Nm3/m3) and in n-C7 conversion (0.1MPa; 350–370°C; WHSV, 1h−1; H2:CH, 10:1mol/mol). The results have shown that at comparable reaction temperatures, i.e. 340–360°C the catalysts containing AlSBA-15 are more active than the catalysts supported on SiO2Al2O3. Among the PtMo/AlSBA-15 catalysts, the catalyst containing 8wt.% of Mo provides the highest selectivity towards i-C16 and the highest iso/n proportion within C10–C15 fraction together with the maintenance of a high conversion. SEM examinations of PtMo catalysts have shown that type of support influences Mo distribution; agglomerates of Mo phases are observed on the AlSBA-15 containing catalysts. It was postulated that the weaker Mo–support interactions and higher acidity in AlSBA-15 supported catalysts resulted in a more active and selective catalyst for hydroconversion of n-hexadecane.

Catalysis in Energy Generation and Conversion: How Insight Into Nanostructure, Composition, and Electronic Structure Leads to Better Catalysts (Perspective)

Catalysts are essential for the generation of energy carriers like hydrocarbon fuels, hydrogen, and electrical current. The performance of catalysts can be related to their nanostructure (i.e., size and shape) and composition. To rationally design catalysts by tuning these properties, they should be measured in a meaningful way using surface-sensitive spectroscopic tools under reaction conditions. In this perspective, we provide case histories of recently published research aimed at understanding these properties using a spectroscopic strategy under reaction conditions. We limit this perspective to studies whose main focus was to understand how the nanostructure and composition impact the active phase and/or efficiency of catalysts for the generation and conversion of energy carriers. We discuss studies of a Pd/Ga2O3 catalyst for the generation of hydrogen fuel from methanol and water, a PtMo catalyst for the generation of hydrogen fuel from biomass and water, Pt/Rh catalysts for the conversion of hydrogen into electrical current, a CeOx catalyst for the conversion of hydrogen into electrical current, and Fe and Co/CoPt catalysts for the generation of hydrocarbon fuel from carbon monoxide and hydrogen. Each study emphasizes how the use of spectroscopic tools under reactive conditions is beneficial for making rational decisions for improving catalysts. The studies demonstrate how different synthesis methods dictate the nanostructure and distribution of alloy components in the catalyst, certain pretreatment conditions create the active surface phase, while reactions and post-treatments can destroy it, and the nanostructure and composition change the electronic structure and alter the selectivity and activity.

A Comparative Study of Carbon-Supported Pt-Mo and Pt-Ru Catalysts for the Anodic Oxidation of Methanol

Different carbon-supported Pt-Mo and Pt-Ru materials were synthesized and a systematic study was carried out in order to evaluate their catalytic activity towards methanol oxidation. Direct current methods were applied in sulfuric acid and methanol - containing electrolytes, in order to evaluate the electrochemical response of the studied electrodes. Pt-Mo catalysts reveal similar performances and, in some cases, higher than Pt-Ru materials. For both catalysts series, it was found that low loadings of the promoting metal (Ru or Mo) improve the methanol oxidation activity. Characterizations by means of transmission electron microscopy and X-Ray Diffraction allowed to measure mean particle sizes below 10 nm for all phases. The Pt-Ru catalysts consist of metallic Pt and metallic ruthenium, while in the The Pt-Mo materials platinum is present in its metallic state and MoO3 is the predominant molybdenum species.

Thermal characterisation of molybdenum and platinum-molybdenum catalysts

Alumina supported Mo and Pt-Mo catalysts was subject to temperature programmed reduction (TPR) using H2 and CO. After earlier oxidation step TPR–H2 profiles shows different surface species, which depends on the composition of the catalysts and reduction temperature. Change in reducing gas from H2 into CO results in significant changes in catalyst system. Hydrogen causes a decrease in oxidation number of metals, while carbon monoxide reacts with chemisorbed chemicals.

Hydrogenation of tetralin over mixed PtMo supported on zirconium doped mesoporous silica: Use of polynuclear organometallic precursors

New mixed PtMo catalysts supported on Zr-doped mesoporous silica have been prepared by using a polynuclear organometallic complex as precursor of the active phase, and tested in the catalytic hydrogenation of tetralin at high hydrogen pressure. The PtMo catalysts have been characterized by XRD, TEM, XPS, N2 sorption at 77K, H2-TPR and NH3-TPD. In order to evaluate the influence of the precursor, a PtMo catalyst has been also prepared from inorganic monometallic salts.The PtMo catalysts were very active in the hydrogenation of tetralin, showing conversion values close to 100%, and high selectivity toward the hydrogenation products (trans- and cis-decalins). The trans- to cis-decalin ratio varies depending on the type of precursor used. The formation of hydrogenolysis, isomerization and cracking products depends on the acidity of the catalysts, although the selectivity towards these products is always lower than 8.5%. On the other hand, all the studied catalysts showed a poor thiotolerance against the presence of dibenzothiophene in the feed.

Role of Pt in high performance Pt-Mo catalysts for hydrotreatment reactions

The effect of Pt/(Pt + Mo) atomic ratio, metal content and the characteristics of the alumina support on activity and synergy in hydrotreatment (HDT) reactions were studied. Pt-Mo supported on different commercial gamma alumina (γ-Al 2O 3) catalysts with different metal contents were prepared and evaluated in simultaneous dibenzothiophene (DBT) hydrodesulfurization (HDS) and naphthalene hydrogenation (HYD) reactions. The characterization of the catalysts was performed using CO chemisorption, proton affinity distribution (PAD) and infrared (IR) spectroscopy of adsorbed NO. The Pt/(Pt + Mo) atomic ratio drastically influences the catalytic behavior. The formation of active sites with high activity and an important synergistic effect is enhanced at a very specific low metals composition of the catalysts. The characterization results suggest that the enhanced HDS and HYD activities are due to an improved dispersion of the active species on the support, which was reached at low metal contents and a specific atomic ratio. Moreover, this improved dispersion was influenced by the surface composition of the alumina and could be associated with a specific interaction between the Pt and the hydroxyl groups of the alumina as well as with the formation and distribution of the Mo active phase exposed on the support.

Sequential determination of platinum, ruthenium, and molybdenum in carbon-supported Pt, PtRu, and PtMo catalysts by atomic absorption spectrometry

A simple accurate and precise analytical method for the determination of platinum, ruthenium, and molybdenum in Pt, PtRu, and PtMo nanoparticles catalysts deposited on high-surface area carbon by flame atomic absorption spectrometry (FAAS) and graphite furnace atomic absorption spectrometry (GFAAS) is described. The complete digestion of samples (0.010–0.020g), which contain noble metals (NMs) in the range between 0 and 30% in combination among them or with other non-NMs, is obtained under mild conditions using both concentrated HCl and HCl+HNO3 (1+1 (v/v)) mixture to boiling for 30min in an open vessel. Carbon is separated from the solution by filtering it. Under optimized conditions of the flame, the poor sensitivity of platinum is enhanced 50-fold in presence of 1% (mV−1) ascorbic acid, whereas the analytical signal of ruthenium increased by the presence of co-existing platinum. Any kind of interference is observed on the analytical signal of molybdenum. Recovery test obtained by analyzing commercial powder catalysts ranged from 99 to 101%. The precision, expressed as relative standard deviation of five measurements, is better than 1%. Electrode catalysts, made by using the carbon-supported platinum-based powder catalysts, have been analyzed for the metal loadings onto the electrode by GFAAS after dissolution under the same conditions used for the powder catalysts. The precision, expressed as relative standard deviation of three measurements, is better than 2%.

PtMo Catalysts for Ultra High CO PEMFC Applications

PtMo Catalysts for Ultra High CO PEMFC Applications