Pd-Pt Catalysts Research Articles

Au-Pd-Pt Multilayer Catalyst for Miniature Fuel Cells

We have developed miniature fuel cells with monolithically fabricated Si electrodes. In the fuel cells, two Si electrodes with porous Pt catalyst layer, which Pt usage was 3.6mg/cm2, were hot-pressed onto either side of a PEM (polymer electrolyte membrane), and the prototype fuel cells showed promising performances of over 500mW/cm2 output at 313K with H2-O2. However, recent improvements of Li-ion battery are lowering expectation to the miniature fuel cells. The advantage of the fuel cell, i.e. clean and efficient energy source, should be strengthened. Bio-mass is an ultimate energy source. Hydrogen can be produced by gasification of the bio-mass in reducing environment, but high CO concentration in the bio-mass derived hydrogen is inevitable. Catalyst poisoning by CO is problematic. We found that our Pd-Pt catalyst obtained by using UPD-SLRR had promising feature. Though the catalyst layer used only 6μg/cm2 of Pt, high tolerance to CO was observed. But Pd and Pt are rare metals, and both amounts should be minimized. In this study, a novel Au-Pd-Pt multilayer catalyst is proposed. Though Au is also a precious metal, reserve of Au is much larger than Pd and Pt, and porous Au can be formed on a Si substrate by similar process to porous Pt. There is no clear evidence, but it is assumed that high CO tolerance of the Pd-Pt catalyst is realized with sub-monolayer Pt on Pd. Hydrogen absorption or stress near the interface between Pd and Pt are sensitive to the number of atomic layer of Pd, and fine control of Pd and Pt deposition on Au is crucial. In our previous study, sub-monolayer Pt was deposited with Cu-UPD, but hydrogen also absorbs on some metal surfaces and form atomic monolayer at slightly under the equilibrium potential. The H-UPD-SLRR can be performed just in an acidic plating bath containing Pd2+ or Pt4+. There is no need to replace the plating bath, and repetition of the atomic layer deposition process will be easy. In this study, basic fabrication strategy of the Au-Pd-Pt multilayer catalyst using H-UPD-SLRR process was examined using Au wire. Preliminary results of cyclic voltammetry suggested that Pd and Pt were successfully deposited on Au wire, and only one Pt deposition cycle on the Au wire with Pd, deposited by several UPD-SLRR cycles, showed large hysteresis loop in the CV, which related to catalytic performance.

SO2 adsorption and desorption characteristics of bimetallic Pd-Pt catalysts: Pd:Pt ratio dependency

SO2 adsorption and desorption, and species formed, on Pd/Pt bimetallic, γ-Al2O3 supported catalysts were characterized as a function of Pd/Pt ratio using DRIFTS and TPD studies. Catalysts with a high Pd content tended to form a greater amount of aluminum sulfate species, which decomposed at high temperature. In contrast, low Pd content catalysts tended to form a greater amount of low-temperature decomposing and desorbing species, such as molecular SO2 and alumina surface sulfite. The amount of SO2 adsorbed and later desorbed during TPD decreased with increasing Pt content in the bimetallic Pd-Pt/Al2O3 catalysts.

Component for Gasoline by Hydroconversion of Furfural Derivates in Presence of Methanol

Hydrotreating of furfural in order to obtain furan derivatives, components for gasoline was studied on two catalysts Ni-Co-Mo /g-Al2O3 promoted with Ba and respectively Pt-Pd/g-Al2O3. Catalysts characterization where performed by determining the acid strength and textural characteristics. For both catalysts the main reaction products identified are tetrahydrofurfuryl alcohol, methyl tetrahydrofurfuryl ether, furfuryl alcohol and furfuryl methyl ether, the most valuable component for gasoline from the resulting mixture being tetrahydrofurfuryl methyl ether. Catalyst Pt-Pd/g-Al2O3 showed higher activity than catalyst Ni-Co-Mo-Ba /g-Al2O3 on the ranges of parameters studied. The yield in ethers was higher than the yield in alcohols for both catalysts for the parameters range studied and the yield in tetrahydrofurfuryl methyl ether was higher in the case of Pd-Pt catalyst than for Ni-Co-Mo-Ba catalyst.

The effect of catalyst precursors and conditions of preparing Pt and Pd-Pt catalysts on their activity in the oxidation of hexane

AbstractThe effectiveness of under-air n-hexane oxidation over monolithic catalysts made of heat-resistant foil, containing Pt, Pd or Pt-Pd, was compared. Pt and Pd precursors, either containing chlorine or devoid of chlorine, were used to prepare the catalysts. The chlorine- containing Pt (H2PtCl6) and Pd (PdCl2) precursors were found to lower the activity of the catalysts in hexane oxidation. Studies of the effect of 0.15% Pt/Al2O3catalyst (using H2PtCl6as the precursor) calcination conditions on catalyst activity showed the catalyst calcined in static air at 500°C to be the most active. Airflow calcination of the catalyst does not change its catalytic properties. In comparison with the 0.5% Pd/Al2O3catalyst obtained from Pd(NO3)2, the use of a bimetallic 0.5% Pd/0.1% Pt/Al2O3catalyst, in which the precursors were Pd(NO3)2and Pt(NO3)4, resulted in the lowering of 10% and 50% n-hexane temperature by 15°C and 10°C.

Effects of Pd doping on N2O formation over Pt/BaO/Al2O3 during NO x storage and reduction process

N2O is a powerful greenhouse gas and plays an important role in destructing the ozone layer. This present work investigated the effects of Pd doping on N2O formation over Pt/BaO/Al2O3 catalyst. Three types of catalysts, Pt/BaO/Al2O3, Pt/Pd mechanical mixing catalyst (Pt/BaO/Al2O3 + Pd/Al2O3) and Pt-Pd co-impregnation catalyst (Pt-Pd/BaO/Al2O3) were prepared by incipient wetness impregnation method. These catalysts were first evaluated in NSR activity tests using H2/CO as reductants and then carefully characterized by BET, CO chemisorption, CO-DRIFTs and H2-TPR techniques. In addition, temperature programmed reactions of NO with H2/CO were conducted to obtain further information about N2O formation mechanism. Compared with Pt/BaO/Al2O3, (Pt/BaO/ Al2O3 + Pd/Al2O3) produced less N2O and more NH3 during NO x storage and reduction process, while an opposite trend was found over (Pt-Pd/BaO/Al2O3 + Al2O3). Temperature programmed reactions of NO with H2/CO results showed that Pd/Al2O3 component in (Pt/BaO/Al2O3 + Pd/Al2O3) played an important role in NO reduction to NH3, and the formed NH3 could reduce NO x to N2 leading to a decrease in N2O formation. Most of N2O formed over (Pt-Pd/BaO/Al2O3 + Al2O3) was originated from Pd/BaO/Al2O3 component. H2-TPR results indicated Pd-Ba interaction resulted in more difficultto- reduce PdOx species over Pd/BaO/Al2O3, which inhibits the NO dissociation and thus drives the selectivity to N2O in NO reduction.

Effect of metal deposition sequence in carbon-supported Pd–Pt catalysts on activity towards CO2 electroreduction to formate

Pd/C catalysts facilitate CO2 electroreduction to formate with high Faradaic efficiency at low overpotentials. However, they are prone to deactivation due to CO poisoning. In this work, three carbon-supported Pd-Pt catalysts with different metal deposition sequences are prepared and their efficacy towards formate production over the Pd surface is studied. X-ray photoelectron spectroscopy and X-ray absorption spectroscopy results show that the surface composition and coordination number of Pd-Pd in carbon-supported Pd-Pt catalysts are greatly influenced by the order in which Pd and Pt nanoparticles (NPs) are deposited. The deposition of Pt NPs prior to Pd NPs on the carbon support gives the best results for formate production with high Faradaic efficiency.

Platinum Inhibits Low-Temperature Dry Lean Methane Combustion through Palladium Reduction in Pd-Pt/Al2 O3 : An In Situ X-ray Absorption Study.

Palladium-platinum bimetallic catalysts supported on alumina with palladium/platinum molar ratios ranging from 0.25 to 4 are studied in dry lean methane combustion in the temperature range of 200 to 500 °C. Platinum addition decreases the catalyst activity, which cannot be explained by the decrease in dispersion or the structure sensitivity of the reaction. In situ X-ray absorption near-edge structure and extended X-ray absorption fine structure spectroscopy measurements have been conducted for monometallic Pd, Pt, and 2:1 Pd-Pt catalysts. Monometallic palladium is fully oxidized in the full temperature range, whereas platinum addition promotes palladium reduction, even in a reactive oxidizing environment. The Pd/PdO weight ratio in bimetallic Pd-Pt 2:1 catalysts decreases from 98/2 to 10/90 in the 200-500 °C temperature range under the reaction conditions. Thus, platinum promotes the formation of the reduced palladium phase with a significantly lower activity than that of oxidized palladium. The study sheds light on the effect of platinum on the state of the active palladium surface under low-temperature dry lean methane combustion conditions, which is important for methane-emission control devices.

Carbon supported PdxPty nanoparticles for oxygen reduction. The effect of Pd:Pt ratio

Studies concentrated on the development of carbon supported PdxPty/C electrocatalysts for the oxygen reduction reaction (ORR). The application of the reverse ‘water-in-oil’ microemulsion method allowed to obtain a number of electrocatalysts with metal nanoparticles of ca. 5–6nm in size. Catalysts with the constant metal loading of 10wt% and various Pd:Pt atomic ratios were investigated. The textural features of the PdPt/C catalysts (surface area, morphology) as well as the PdPt phase (metal particle size, bulk composition) were characterized by a number of techniques. A particular attention was paid to the characterization of the surface properties of the PdPt particles using cyclic voltammetry technique. For all Pt contents (5 to 70 at%) a segregation of metal components (Pt, Pd) occurred leading to the Pt enrichment in the top layers. The observed Pt enrichment manifested especially strongly for PdPt catalysts with bulk Pt content below 20 at%. The surface fraction of Pt as high as 0.8 to 0.9 was attained regardless of nominal Pt content, starting from 30 at%. Among the catalysts, those with Pt content of 50 and 70 at% exhibited the highest activity towards ORR in terms of positively shifted half-wave potential, even surpassing that of Pt/C. Moreover, the obtained specific activity and turnover frequency values also suggested similar activities of catalysts with Pt content of 50 and 70 at%. A negligible formation of hydrogen peroxide on these two catalysts, indicated almost exclusively a desired four-electron process leading to water formation. The observed effect of Pt content on ORR activity is discussed in terms of surface properties of the PdPt nanoparticles.

Miniature Fuel Cell With Monolithically Fabricated Si Electrodes - Au-Pd-Pt Multilayer Catalyst -

A novel catalyst layer structure is proposed for our miniature fuel cells. In our fuel cells, conventionally porous Pt was used as a catalyst layer. In order to reduce the Pt amount, instead of porous Pt, porous Pd was formed on a Si chip and Pt was deposited atomically on the Pd by UPD-SLRR(Under Potential Deposition - Surface Limited Redox Replacement). The Pd- Pt catalyst showed satisfying performance, besides high CO tolerance was observed. Though the Pd-Pt catalyst is quite promising, Pd is also a rare metal and reduction of Pd amount is necessary. In this study, a novel Au-Pd-Pt catalyst formation strategy is proposed by UPD-SLRR, and the layered structure is preliminary fabricated.

Dechlorination of Dichloromethane by Hydrotreatment with Bimetallic Pd-Pt/C Catalyst

A bimetallic Pd-Pt catalyst (0.5 and 0.9% w/w of Pd and Pt, respectively) supported on activated carbon has been prepared and tested for hydrodechlorination of dichloromethane (DCM). Different reduction temperatures were used during the catalyst synthesis, and the catalyst reduced at 250 °C was tested under varying reaction conditions, which included H2/DCM molar ratio, inlet DCM concentration, reaction temperature and space-time, always at 1 atm pressure. Formation of bimetallic particles was evidenced by TEM. Complete dechlorination was achieved at 250 °C, 2.5 kg h mol−1 space-time and H2/DCM = 50.

Stability of an acid activated carbon based bifunctional catalyst for the raw bio-oil hydrodeoxygenation

The performance (activity, selectivity and stability) of a Pt-Pd catalyst supported on a phosphorus-containing activated carbon (ACP) has been studied in the hydrodeoxygenation (HDO) of raw bio-oil, and compared with another bifunctional catalyst prepared with a FCC (Fluid Catalytic Cracking) catalyst as acid support. Experiments have been carried out in a fixed bed reactor under the following conditions: 400–450°C; 65bar; space time, 0.18gcat hg−1bio-oil; H2:bio-oil ratio, 20cm3H2 (STP) cm−3bio-oil; time on stream, 0–10h. The catalyst reaches a pseudo-steady state at 450°C after 6h of time on stream, preserving a constant activity as a consequence of the simultaneous formation and hydrocracking of the deposited coke. In these conditions, the yield of C5+ hydrocarbons is 20wt%. This organic liquid fraction mainly contains aromatics, and thus, it may require an additional mild hydrocracking treatment for its valorization as fuel. On the other hand, the gas fraction obtained can be used directly as fuel, and the aqueous liquid fraction (with a high concentration of methanol, 58wt%) is interesting as co-feedstock with methanol in a methanol to olefins (MTO) unit.

Miniature Fuel Cell with Monolithically Fabricated Si Electrodes -Fabrication of Pd-Pt Catalyst By H-UPD-Slrr-

Miniature fuel cells have attracted attention as an ultimate portable power source, and we have developed monolithically fabricated Si electrodes for the miniature fuel cells[1]. Recent prototypes showed satisfying power density about 500mW/cm2 at 313K though the reaction area was only 1 mm2. Besides, the prototype cells used porous Pt as a catalyst layer, and the amount of Pt was quite large. 3.6mg/cm2of Pt was used and the amount of Pt must be reduced. Then, to reduce the Pt amount, slight deposition of Pt on porous Pd was attempted using UPD-SLRR (Underpotential Deposition, and Surface Limited Redox Replacement), and obtained Pd-Pt catalyst showed quite promising results[2]. Furthermore, preliminary results suggested that the Pd-Pt catalyst had high CO tolerance. We are also interested in the use of biomass derived hydrogen for our miniature fuel cells and the high CO tolerance is strongly needed. Therefore, further study of the Pd-Pt catalyst obtained using the UPD-SLRR technique. However, Cu UPD was used for SLRR and the reproducibility was not good enough, because bath change was needed between UPD and SLRR processes, and Cu oxidation was not negligible. Recently, Nutariya et al. reported that UPD-SLRR reaction is available using hydrogen UPD[3]. If this process could be applied to our porous Pd as shown in figure 1, no bath change is needed and repetitive deposition of Pt or other noble metal would be realized, and optimization of the Pd-Pt catalyst would be possible. In this study, Pt deposition on the porous Pd was attempted by H-UPD-SLRR process, and the power generation by the obtained fuel cells was demonstrated. Experimental The Si substrate used in this study was N-type (Resistivity 0.004-0.006 Ohm-cm), (100) oriented, double side mirror polished and 100 um thick wafer. The porous Pd was formed on a Si substrate using anodize porous Si. H-UPD-SLRR was performed on the porous Pd in a solution of 1mM H2PtCl6 and 0.1 M HClO4. MSE was used as a reference electrode. As a counter electrode, Pt wire was used. The electrolyte solution was deaerated for 30 minutes with N2 gas and the whole vessel for the H-UPD-SLRR was filled with N2 during the experiment. H-UPD process was performed at -600mV vs. MSE for 30 seconds. Subsequently, SLRR process was performed by opening the circuit until the electrode potential reached -280mV vs. MSE. Using the slightly Pt deposited porous Pd layer was used as catalyst layers, prototype fuel cells were built. Power generation tests were performed by the cells whose anode and cathode catalysts were Pd-Pt and Pt, respectively. Prototype cells were set into the aluminum casing at 313K in a temperature controllable chamber. 10 sccm pure hydrogen or hydrogen containing 100ppm CO were supplied to the anode. 5sccm oxygen was supplied to the cathode. Power generation was performed for more than 1 hour, and tolerance of the catalyst to the CO poisoning was observed. Results Figure 2 shows cross sectional SEM image of the porous Pd-Pt catalyst layer. Cross sectional EDS analysis of the porous Pd-Pt catalyst layer showed slight Pt deposition, and it seemed that expected reaction was realized(figure 3). The amount of Pt was estimated to be about 20 μg/cm2from the charge of underpotential H deposition. Figure 4 shows preliminary result of power generation test of Pd-Pt catalyst. Red line shows the polarization curve with pure hydrogen supply, and blue line shows polarization curve with hydrogen containing 100 ppm CO. Though the power density was dropped with 100 ppm CO, the power density kept almost constant more than 1h, though conventional catalyst shows quick power drop with 100ppm CO. With these results, CO tolerance was reconfirmed with Pd-Pt catalyst obtained by novel H-UPD-SLRR process. With the H-UPD-SLRR process, amount of Pt deposition can be finely controlled, and further optimization of the catalyst will be performed.

Development of advanced catalytic layer based on vertically aligned conductive polymer arrays for thin-film fuel cell electrodes

Abstract The degradation of carbon supports significantly influences the performance of proton exchange membrane fuel cells (PEMFCs), particularly in the cathode, which must be overcome for the wide application of fuel cells. In this study, advanced catalytic layer with electronic conductive polymer–polypyrrole (PPy) nanowire as ordered catalyst supports for PEMFCs is prepared. A platinum–palladium (PtPd) catalyst thin layer with whiskerette shapes forms along the long axis of the PPy nanowires. The resulting arrays are hot-pressed on both sides of a Nafion® membrane to construct a membrane electrode assembly (without additional ionomer). The ordered thin catalyst layer (approximately 1.1 μm) is applied in a single cell as the anode and the cathode without additional Nafion® ionomer. The single cell yields a maximum performance of 762.1 mW cm−2 with a low Pt loading (0.241 mg Pt cm−2, anode + cathode). The advanced catalyst layer indicates better mass transfer in high current density than that of commercial Pt/C-based electrode. The mass activity is 1.08-fold greater than that of DOE 2017 target. Thus, the as-prepared electrodes have the potential for application in fuel cells.

Methanol-Tolerant Platinum-Palladium Catalyst Supported on Nitrogen-Doped Carbon Nanofiber for High Concentration Direct Methanol Fuel Cells.

Pt-Pd catalyst supported on nitrogen-doped carbon nanofiber (N-CNF) was prepared and evaluated as a cathode electrode of the direct methanol fuel cell (DMFC). The N-CNF, which was directly synthesized by the catalytic chemical vapor deposition from acetonitrile at 640 °C, was verified as having a change of electrochemical surface properties such as oxygen reduction reaction (ORR) activities and the electrochemical double layer compared with common carbon black (CB). To attain the competitive oxygen reduction reaction activity with methanol tolerance, the Pt and Pd metals were supported on the CB or the N-CNF. The physical and electrochemical characteristics of the N-CNF–supported Pt-Pd catalyst were examined and compared with catalyst supported on the CB. In addition, DMFC single cells using these catalysts as the cathode electrode were applied to obtain I-V polarization curves and constant current operating performances with high-concentration methanol as the fuel. Pt-Pd catalysts had obvious ORR activity even in the presence of methanol. The higher power density was obtained at all the methanol concentrations when it applied to the membrane electrode assembly (MEA) of the DMFC. When the N-CNF is used as the catalyst support material, a better performance with high-concentration methanol is expected.

Synergistic Effects of Bimetallic PtPd/TiO2 Nanocatalysts in Oxidation of Glucose to Glucaric Acid: Structure Dependent Activity and Selectivity

Direct oxidation of glucose with enhanced selectivity to glucaric acid with tartronic and oxalic acids as coproducts is reported using bimetallic PtPd/TiO2 catalysts under mild conditions. Bimetallic PtPd catalysts display significantly enhanced catalytic activity (turnover frequency (TOF) 2404 h–1) and improved selectivity to glucaric acid (S 44%) in glucose oxidation compared to monometallic catalysts (TOF 248 h–1, S 4%). Oxidation of glucose follows a consecutive reaction with gluconic acid as an intermediate with inhibition of the second step (to glucaric acid and C–C cleavage reactions) by the presence of glucose. Surface characterization using TEM, SEM, chemisorption, UV–vis spectroscopy, and XRD distinguished the particle morphologies and provided insights into structure–activity relations. A reaction pathway for glucose oxidation is proposed based on the product distribution. These results provide new insights into the design of bimetallic catalysts for the oxidation of glucose to glucaric acid.

A green synthesis of “naked” Pt and PtPd catalysts for highly efficient methanol electrooxidation

A green synthesis of “naked” Pt and PtPd catalysts with clean surfaces is proposed for highly efficient methanol electrooxidation.

Vapor-Deposited Pt and Pd-Pt Catalysts for Solid Acid Fuel Cells: Short Range Structure and Interactions with the CsH2PO4 Electrolyte

State-of-the-art cathodes for solid acid fuel cells (SAFCs) based on the crystalline electrolyte CsH2PO4 (CDP) are comprised of a proton-conducting CDP network coated by a vapor-deposited nanostructured catalyst. Pd-rich (85 at%Pd) Pt-Pd oxygen reduction catalysts vapor-deposited on CDP display both extraordinary activity for oxygen reduction and poor stability in cathodes for SAFCs operating at 250 °C. Similar catalysts with lower Pd content (57 at%Pd) are less active and more stable. Using X-ray absorption spectroscopy (XAS), we find that these catalysts are structurally similar and that structural variations are insufficient to explain the observed differences in activity. XAS and solid-state and solution nuclear magnetic resonance (NMR) also show that additional water-soluble chemical species are present in the Pd-rich electrode after fuel cell operation. We attribute the presence of these species to the reactivity of the Pd-rich catalyst with CsH2PO4 and suggest that these products are the cause of the observed deactivation.

Comparative study to understand the intrinsic properties of Pt and Pd catalysts for methanol and ethanol oxidation in alkaline media

The understanding of the intrinsic properties of Pt and Pd is important for the rational design of catalysts for methanol and ethanol oxidation in alkaline media. In this paper, Pd catalysts, Pt catalysts and bimetallic PtPd catalysts supported on nitrogen-doped graphene are investigated. The cyclic voltammograms (CVs) for the bimetallic catalysts in 1M KOH solution demonstrate the increasing surface composition of Pt versus Pd. The linear sweep voltammetry results show that the onset potential for OH formation on Pt is lower than on Pd, indicating that Pt has a higher affinity for OH than Pd. The CVs recorded for methanol and ethanol oxidation show that ethanol oxidation occurs at lower potentials, suggesting that ethanol is a more active fuel than methanol. Ethanol and methanol oxidation occurs at lower potentials on Pt than on Pd, revealing that Pt is intrinsically more active than Pd. Chronoamperometry results show that the rate of catalysts deactivation during ethanol oxidation is more severe compared with methanol oxidation, especially for catalysts with higher Pt content. The possible reason for the deactivation behaviors is presented and recommendations are given for future catalysts development.

PdPt catalyst synthesized using a gas aggregation source and magnetron sputtering for fuel cell electrodes

PdPt catalysts with different morphologies and atomic ratios have been synthesized on native SiO2/Si and on proton exchange membranes. The combination of the gas aggregation source and magnetron sputtering techniques allows the formation of quasi core-shell Pd0.97Pt0.03@Pt nanoclusters. Transmission electron microscopy and grazing incidence wide-angle x-ray scattering measurements of the Pd-rich core reveal a mean diameter of 4 nm and a face-centered cubic structure. The Pt shell around half of the Pd-rich core is formed by magnetron sputtering, and increases the nanocluster diameter (up to 10 nm) and the overall Pt content (up to 85%). Membranes coated by the PdPt core catalyst and PdPt@Pt catalyst (resulting in the formation of catalyst-coated membranes) are incorporated into fuel cells and their electrical characteristics are measured. The association of the two deposition techniques results in the formation of quasi core-shell PdPt@Pt nanoclusters, improving the start-up step of the fuel cell.

The Effect of Phosphorus Exposure on Diesel Oxidation Catalysts—Part I: Activity Measurements, Elementary and Surface Analyses

The effects of phosphorus poisoning on the activity of PtPd and Pt diesel oxidation catalysts and on the activity of the support material were investigated using the gas phase laboratory-scale-aging procedure. The catalysts were treated using two different phosphorus concentrations (0.065 and 0.13 mol/L (NH4)2HPO). The deactivation was studied by inductively coupled plasma optical emission spectroscopy, electron microscopy, X-ray diffractometry, X-ray photoelectron spectrometry and Fourier-transform infrared reflectance, N2-physisorption, and activity measurements with CO, C3H6 and NO. The amount of accumulated phosphorus was higher on the Pt catalyst surface than on the PtPd catalyst and significantly higher on the surface of the bare support material. Phosphorus concentration was uniform throughout the support layer (down to the 10 μm), and phosphorus was found as phosphate, although it can also form compounds like AlPO4 with the support. The treatment with low phosphorus concentration was found to have a clear deactivation effect only for C3H6 oxidation activity on PtPd catalysts above 200 °C. The treatment with high phosphorus concentration significantly decreased the activity of both the PtPd and Pt catalysts. In particular, the C3H6 and NO oxidation activities of the fresh and P-treated Pt catalysts were higher than those of the PtPd catalysts for the entire temperature range.