PT Content Research Articles

Electrochemical Behavior of Pt–Ru Catalysts Supported on Graphitized Ordered Mesoporous Carbons toward CO and Methanol Oxidation

In this work, graphitized ordered mesoporous carbons (gCMK-3) were employed as support for Pt and Pt–Ru nanoparticles synthesized by different reduction methods. The catalysts displayed metal contents and Pt:Ru atomic ratios close to 20 wt % and 1:1, respectively. A comparison of the physical parameters of Pt and Pt–Ru catalysts demonstrated that Ru enters into the Pt crystal structure, with well-dispersed nanoparticles on the carbon support. The Pt catalysts exhibited similar surface oxide composition, whereas a variable content of surface Pt and Ru oxides was found for the Pt–Ru catalysts. As expected, the Pt–Ru catalysts showed low CO oxidation onset and peak potentials, which were attributed to the high relative abundances of both metallic Pt and Ru oxides. All the studied catalysts exhibited higher maximum current densities than those observed for the commercial Pt and Pt–Ru catalysts, although the current–time curves at 0.6 V vs. reversible hydrogen electrode (RHE) demonstrated a slightly higher stationary current density in the case of the Pt/C commercial catalyst compared with Pt nanoparticles supported on gCMK-3s. However, the stationary currents obtained from the Pt–Ru/gCMK-3 catalysts surpassed those of the commercial Pt–Ru material, suggesting the suitability of the prepared catalysts as anodes for these devices.

Ag-Nb-Pt Bazlı SCR Katalizör Karakterizasyonu

Selective Catalytic Reduction (SCR) is an emission control system used in diesel engines to reduce NOx emissions. In this study, synthesized of catalyst for SCR system was investigated as experimentally. For this purpose, silver nitrate (AgNO3), niobium (V) chloride (NbCl5) and tetra amine platinum (II) nitrate (Pt(NH3)4(NO3)2) were used to coat the cordierite (2Al2O3-5SiO2-2MgO) structure with impregnation method. X-ray Fluorescence (XRF), Scanning Electron Microscope (SEM) and Brunauer, Emmett, and Teller (BET) analyzes were carried out in order to determine the chemical and physical properties of the catalyst. Results showed that the coating materials penetrate the entire surface of the pores. It was also determined that the BET specific surface areas of the produced catalyst and cordierite are 0.2918 m2/g and 0.4568 m2/g, respectively. The reduction of surface area could be attributed to the increment of crystallization with chemical reactions occurred at the high sintering temperature. Besides, XRF analysis results demonstrated that content of Ag, Pt and Nb in the in the catalyst was found to be 3.67%, 0.19% and 0.12%, respectively, whereas Ag content in cordierite structure was 0.03%. 

Cobalt oxyhydroxide and carbon dots modified by platinum as superior electrocatalyst for methanol oxidation

The engineering of electrocatalysts with high performance for methanol oxidation reaction (MOR) is of great urgency for the development of direct methanol fuel cells (DMFCs). Here, we designed and fabricated cobalt oxyhydroxide and carbon dots modified by platinum (Pt-CoOOH-CDs/C) hybrids with low content of Pt (13 wt%) as electrocatalyst, which exhibit high activity (856.3 mA·mg−1Pt), stability (3 h) and better anti-poisoning ability for MOR. The Pt-CoOOH-CDs/C was synthesized by precipitate method followed with photochemical deposition. In the catalytic system, the Pt nanoparticles serve as the active center toward MOR, CoOOH-CDs use as the co-catalyst to oxidize CO-like poisonous species to CO2 on neighbouring Pt sites, and the cost-efficient carbon black enhances the conductivity for the system. The cost-efficient Pt-CoOOH-CDs/C system with improved kinetics for anodic methanol oxidation has promising application in alkaline DMFCs.

The Fate of Platinum-Group Minerals in the Exogenic Environment—From Sulfide Ores via Oxidized Ores into Placers: Case Studies Bushveld Complex, South Africa, and Great Dyke, Zimbabwe

Diverse studies were performed in order to investigate the behavior of the platinum-group minerals (PGM) in the weathering cycle in the Bushveld Complex of South Africa and the Great Dyke of Zimbabwe. Samples were obtained underground, from core, in surface outcrops, and from alluvial sediments in rivers draining the intrusions. The investigations applied conventional mineralogical methods (reflected light microscopy) complemented by modern techniques (scanning electron microscopy (SEM), mineral liberation analysis (MLA), electron-probe microanalysis (EPMA), and LA-ICPMS analysis). This review aims at combining the findings to a coherent model also with respect to the debate regarding allogenic versus authigenic origin of placer PGM. In the pristine sulfide ores, the PGE are present as discrete PGM, dominantly PGE-bismuthotellurides, -sulfides, -arsenides, -sulfarsenides, and -alloys, and substantial though variable proportions of Pd and Rh are hosted in pentlandite. Pt–Fe alloys, sperrylite, and most PGE-sulfides survive the weathering of the ores, whereas the base metal sulfides and the (Pt,Pd)-bismuthotellurides are destroyed, and ill-defined (Pt,Pd)-oxides or -hydroxides develop. In addition, elevated contents of Pt and Pd are located in Fe/Mn/Co-oxides/hydroxides and smectites. In the placers, the PGE-sulfides experience further modification, whereas sperrylite largely remains a stable phase, and grains of Pt–Fe alloys and native Pt increase in relative proportion. In the Bushveld/Great Dyke case, the main impact of weathering on the PGM assemblages is destruction of the unstable PGM and PGE-carriers of the pristine ores and of the intermediate products of the oxidized ores. Dissolution and redistribution of PGE is taking place, however, the newly-formed products are thin films, nano-sized particles, small crystallites, or rarely µm-sized grains primarily on substrates of precursor detrital/allogenic PGM grains, and they are of subordinate significance. In the Bushveld/Great Dyke scenario, and in all probability universally, authigenic growth and formation of discrete, larger PGM crystals or nuggets in the supergene environment plays no substantial role, and any proof of PGM “neoformation” in a grand style is missing. The final PGM suite which survived the weathering process en route from sulfide ores via oxidized ores into placers results from the continuous elimination of unstable PGM and the dispersion of soluble PGE. Therefore, the alluvial PGM assemblage represents a PGM rest spectrum of residual, detrital grains.

Facile synthesis of trimetallic PtAuCu alloy nanowires as High−Performance electrocatalysts for methanol oxidation reaction

The high cost, easy to be poisoned and poor stability of platinum (Pt) catalysts have limited their further application in various fields. The ability to impart Pt−based catalysts with high catalytic activity and low cost is critical to advancing fuel cell technologies. A promising strategy is applied to design Pt−based bimetallic or trimetallic nanostructures. The method of increasing electrocatalytic activity performance has attracted considerable attention by introducing other metal atoms for their unique structures and compositions. In this study, we report a solvothermal synthesis of trimetallic Pt−based (PtAuCu) alloy nanowires with controlled percentages of individual metals. By optimizing the content of Pt, Au and Cu, the trimetallic PtAuCu NWs nanowires show superior electrocatalytic activity toward methanol oxidation reaction (MOR). This enhanced electrocatalytic activity is due to the synergistic interactions of different metals. In particular, the incorporation of Cu can effectively reduce the use of precious metal Pt. And during the MOR process, the dissolution of Cu atoms from the PtAuCu surface, which can be attributed to a dealloying process, providing more Pt active sites for MOR thus enhancing the electrochemical activity. The electrochemical active surface area (ECSA) and mass activity of the Pt50Au10Cu40 alloy catalyst is approximately 1.5 and 4.34 times of commercial Pt/C catalyst, respectively. Moreover, it exhibits superior stability after 10000 s compared with the other catalysts. Thus, the multi−metal doping in Pt catalyst not only decreases the cost of Pt, but also exhibits a significant electrocatalytic performance, which is prospective for direct alcohol fuel cells.

Study of platinum and palladium distribution in advanced materials based on tin dioxide using inductively coupled plasma mass spectrometry (ICP-MS)

Inductively coupled plasma mass spectrometry (ICP-MS) is used for separate determination of platinum and palladium on the surface and in the bulk of tin dioxide based nanocomposites. Synthesis of SnO2 matrices was conducted using deposition from the solution and flame spray pyrolysis (FSP). The modifiers were injected by impregnation via the dispersion of the matrix powders in the solutions of precursors in volatile solvents and subsequent evaporation of the solvent. It is shown that palladium is present on the surface of the nanocomposites regardless of the synthesis procedure. As the losses of the modifier after impregnation of SnO2synthesized by FSP method were obserbed, we concluded that the properties of the SnO2surface depend on the method of obtaining matrix. It was also shown that for the materials obtained by the method of deposition from the solutions 30 - 50% Pt are present on the surface and other 50 - 70% are distributed in the bulk of SnO2. The use of pyrolysis in the flames makes it possible to increase the content of Pt on the surface up to 80%. The loss of Pt observed in both cases and attributed to the differences in the microstructure of SnO2results in the etherification of thin layers of phases of complex composition which affect the processes of superficial diffusion and evaporation. Reproducibility of the results of Pt and Pd determination indicates to a high degree of heterogeneity of the studied materials.

Highly sensitive detection of nitrite at a novel electrochemical sensor based on mutually stabilized Pt nanoclusters doped CoO nanohybrid

A novel, low-cost and mutually stable Pt nanocluster doped nanoporous CoO (Pt/CoO) has been successfully designed and synthesized by facilely dealloying Al85Co14Pt1 ternary alloy in alkaline solution. Electronic microscope images demonstrated the Pt nanoclusters are doped inside of the CoO crystal structure and they were mutually stabilized with each other, resulting in a high electrocatalytical activity even if the content of Pt was extremely low. A new electrochemical sensor was then constructed by modifying the Pt/CoO nanohybrid on a glassy carbon electrode, which enabled amperometric sensing of nitrite with wide linear ranges of 0.2 μM-3.67 mM and 3.67–23.7 mM, high sensitivities of 901.4 and 408.5 μA mM−1 cm-2 as well as a low detection limit of 0.067 μM (S/N = 3). Furthermore, the sensor showed good selectivity, stability and reproducibility towards nitrite detection. The feasibility of the electrochemical sensor was proved by successful detection of nitrite in real samples.

Platinum Recovery from Industrial Process Solutions by Electrodeposition-Redox Replacement.

In the current study, platinum—present as a negligible component (below 1 ppb, the detection limit of the HR-ICP-MS at the dilutions used) in real industrial hydrometallurgical process solutions—was recovered by an electrodeposition–redox replacement (EDRR) method on pyrolyzed carbon (PyC) electrode, a method not earlier applied to metal recovery. The recovery parameters of the EDRR process were initially investigated using a synthetic nickel electrolyte solution ([Ni] = 60 g/L, [Ag] = 10 ppm, [Pt] = 20 ppm, [H2SO4] = 10 g/L), and the results demonstrated an extraordinary increase of 3 × 105 in the [Pt]/[Ni] on the electrode surface cf. synthetic solution. EDRR recovery of platinum on PyC was also tested with two real industrial process solutions that contained a complex multimetal solution matrix: Ni as the major component (>140 g/L) and very low contents of Pt, Pd, and Ag (i.e., <1 ppb, 117 and 4 ppb, respectively). The selectivity of Pt recovery by EDRR on the PyC electrode was found to be significant—nanoparticles deposited on the electrode surface comprised on average of 90 wt % platinum and a [Pt]/[Ni] enrichment ratio of 1011 compared to the industrial hydrometallurgical solution. Furthermore, other precious metallic elements like Pd and Ag could also be enriched on the PyC electrode surface using the same methodology. This paper demonstrates a remarkable advancement in the recovery of trace amounts of platinum from real industrial solutions that are not currently considered as a source of Pt metal.

Pt-Embedded CuO x-CeO2 Multicore-Shell Composites: Interfacial Redox Reaction-Directed Synthesis and Composition-Dependent Performance for CO Oxidation.

Exploring the state-of-the-art heterogeneous catalysts has been a general concern for sustainable and clean energy. Here, Pt-embedded CuO x-CeO2 multicore-shell (Pt/CuO x-CeO2 MS) composites are fabricated at room temperature via a one-pot and template-free procedure for catalyzing CO oxidation, a classical probe reaction, showing a volcano-shaped relationship between the composition and catalytic activity. We experimentally unravel that the Pt/CuO x-CeO2 MS composites are derived from an interfacial autoredox process, where Pt nanoparticles (NPs) are in situ encapsulated by self-assembled ceria nanospheres with CuO x clusters adhered through deposition/precipitation-calcination process. Only Cu-O and Pt-Pt coordination structures are determined for CuO x clusters and Pt NPs in Pt/CuO x-CeO2 MS, respectively. Importantly, the close vicinity between Pt and CeO2 benefits to more oxygen vacancies in CeO2 counterparts and results in thin oxide layers on Pt NPs. Meanwhile, the introduction of CuO x clusters is crucial for triggering synergistic catalysis, which leads to high resistance to aggregation of Pt NPs and improvement of catalytic performance. In CO oxidation reaction, both Ptδ+-CO and Cu+-CO can act as active sites during CO adsorption and activation. Nonetheless, redundant content of Pt or Cu will induce a strongly bound Pt-O-Ce or Cu-[O x]-Ce structures in air-calcinated Pt/CuO x-CeO2 MS composites, respectively, which are both deleterious to catalytic reactivity. As a result, the composition-dependent catalytic activity and superior durability of Pt/CuO x-CeO2 MS composites toward CO oxidation reaction are achieved. This work should be instructive for fabricating desirable multicomponent catalysts composed of noble metal and bimetallic oxide composites for diverse heterogeneous catalysis.

Heavy metal mobility and valuable contents of processed municipal solid waste incineration residues from Southwestern Germany

As conventional end-of-life disposal, municipal solid waste (MSW) incineration residues can be problematic due to potential release of toxic compounds into the environment. Using municipal solid waste incineration residues as urban-mine of valuable metals (e.g. precious metals) could provide a trash-to-treasure possibility. The objectives of the study are to (i) determine the contents of different contaminant metallic elements (Zn, Cu, Ba, Pb, Cr and Ni) in four size fractions of MSW incineration residues and discuss their mobility potential by using the modified BCR sequential extraction method; (ii) investigate the level of valuable critical contents (precious metals, rare earth elements, etc.) in these wastes. We also characterized mineralogy and elemental composition of four different grain size fractions (0–0.5, 0.5–2.0, 2.0–4.0 and 4.0–16.0 mm) of processed municipal solid waste incineration residue (PIR) from the Southwestern region of Germany, using X-ray fluorescence, X-ray powder diffraction and different spectroscopic techniques. Among all studied size fractions, grains smaller than 2 mm contained higher amounts of total extractable heavy metals in most cases. The most important finding of the study is that the total contents of Cu, Au and Pt in the incineration residues reached economically profitable levels (5.1 g/kg, 21.69 mg/kg and 17.45 mg/kg, respectively).

Stability of nanostructured silver-platinum alloys

The stability of Ag-Pt systems: 13-atoms icosahedral cluster model (Ag13-nPtn) and 54-atoms (111) surface slab model (45Ag9Pt) have been systematically investigated by using Density Functional Theory within the generalized gradient approximation (DFT–GGA). Experimentally tested resistance of AgPt alloy nanoparticles supported on silica to decay upon temperature treatment (423 K–573 K in N2 flow) have shown to correlate with theoretical results. The stability of the clusters as a function of AgPt composition decreases with increasing content of Pt. The general stability trend of the AgPt alloy was maintained, in theory and experiment, for the Ag/Pt molar ratio of 1.6–5.1. Two particularly stable Ag/Pt compositions were revealed: 1.6 and 0.4. It was also found that surface location of platinum is responsible for stabilization of the Ag-Pt nanostructured alloy.

Ultra-low content of Pt modified CdS nanorods: Preparation, characterization, and application for photocatalytic selective oxidation of aromatic alcohols and reduction of nitroarenes in one reaction system.

A series of Pt nanoparticles (with size of 3-4 nm) decorated CdS nanorods were prepared via a simple solvothermal method. The samples were then used for photocatalytic selective oxidation (SO) of aromatic alcohols and reduction (SR) of nitroarenes in one reaction system. The platinized samples showed enhanced activity for the conversions than pristine CdS as Pt can serve as e- trapping and reaction sites, by which the recombination of photoinduced charge carriers can be suppressed and the adsorption of reactants and the SR of nitroarenes can be promoted. The sample loaded with only of 0.03% Pt showed the highest performance and, after irradiation for 4 h, the conversions of p-methoxybenzyl alcohol and nitrobenzene are as high as 92.7% and 94.8%, while the yields of p-methoxybenzaldehyde and aniline are 80.5% and 36.0%. The activities are about 2.0 times higher than that of CdS. The coupling reaction mechanism for the SO of aromatic alcohols to aldehydes and SR of nitroarenes to anilines in the reaction system was finally proposed.

A New Strategy for Outstanding Performance and Durability in Acidic Fuel Cells: A Small Amount Pt Anchored on Fe, N co‐Doped Graphene Nanoplatelets

AbstractDevelopment of cost‐effective and efficient electrocatalysts for the oxygen reduction reaction (ORR) is one of the most important topics in the polymer electrolyte membrane fuel cells (PEMFCs). Herein, we suggested the enhanced electrochemical catalyst with nanoscale platinum anchored on iron (Fe) and nitrogen (N) co‐doped graphene nanoplatelets (Pt/FeN‐GnPs) with low content of Pt. The nanoscale platinum particles are uniformly anchored on the surface of FeN‐GnPs and result in excellent oxygen reduction activity and stability in acidic media. The fascinating interaction between Pt particles and FeN−GnPs substrate contributed to advanced oxygen reduction activity, outstanding cell performance, and remarkable high stability for acidic PEM fuel cells.

Enhanced Photocatalytic H2-Production Activity of g-C3N4 Nanosheets via Optimal Photodeposition of Pt as Cocatalyst

Photocatalytic H2 production plays an important role in alleviating fossil fuel crisis and constructing a sustainable world. Graphitic carbon nitride nanosheets (CNS), coupled with cocatalyst platinum (Pt) and hole sacrificial agent triethanolamine (TEOA), often show excellent H2-production activity. However, the question on maximizing Pt amount in this given TEOA-contained system still remains unsolved. Herein, it was found that the order of adding TEOA into the reaction system before or after the photodeposition of Pt had a significant effect on photocatalytic hydrogen production over CNS. Specifically, the content of Pt was lower when TEOA was added beforehand, implying that a strong interaction existed between the Pt-precursor H2PtCl6 and TEOA, thus curbing the photoreduction to metallic Pt. Therefore, a roughly 4-fold increment in hydrogen production activity (4210.8 vs. 972.2 μmol h–1 g–1) was obtained by merely swapping the sequence of the addition of TEOA. Moreover, the apparent quantum efficiency...

Nitrogen-doped porous carbon derived from ZIF-8 as a support of electrocatalyst for enhanced oxygen reduction reaction in acidic solution

The composites of platinum (Pt) nanoparticles (NPs) loaded on nitrogen-doped porous carbon (NPC) derived from ZIF-8 were successfully prepared based on double solvent impregnation and chemical reduction methods. By changing the calcination temperature and duration of ZIF-8, the concentration of nitrogen doping and bonding properties in the porous carbon can be well regulated, which is helpful to manipulate the crystal orientation of Pt nanoparticles and their dispersion and loading on the NPCs. Consequently, an improved oxygen reduction reaction (ORR) catalytic activity was successfully demonstrated in the optimized [email protected] composite with relatively lower content of Pt compared to the commercial catalyst Pt/C (20 wt%, JM). Moreover, the exceptional stability of the composite catalyst during ORR was experimentally verified by both the accelerated durability tests (ADT) and chronoamperometric i–t measurements. Intrinsically, pyridinic-N and graphitic-N were believed to be beneficial to the improved catalytic performance in the composite, while graphitic-N and pyridine-N-oxide were verified to be helpful to improve the stability as they can act as anchor of Pt NPs.

Tailoring Platinum(IV) Amphiphiles for Self-Targeting All-in-One Assemblies as Precise Multimodal Theranostic Nanomedicine.

Drug, targeting ligand, and imaging agent are the three essential components in a nanoparticle-based drug delivery system. However, tremendous batch-to-batch variation of composition and drug content typically accompany the current approaches of building these components together. Herein, we report the design of photoactivatable platinum(IV) (Pt(IV)) amphiphiles containing one or two hydrophilic lactose targeting ligands per hydrophobic Pt(IV) prodrug for an all-in-one precise nanomedicine. Self-assembly of these Pt(IV) amphiphiles results in either micelle or vesicle formation with a fixed Pt/targeting moiety ratio and a constantly high content of Pt. The micelles and vesicles are capable of hepatoma cell-targeting, fluorescence/Pt-based CT imaging and have shown effective anticancer efficacy under laser irradiation in vitro and in vivo. This photoactivatable, active self-targeting, and multimodal theranostic amphiphile strategy shows great potential in constructing precise nanomedicine.

Compositional segregation and electrical properties characterization of [001]- and [011]-oriented co-growth Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystal

A Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 relaxor ferroelectric single crystal boule of 3 in. diameter was grown using [001]- and [011]-oriented co-growth crystals as seeds by the modified Bridgman method. The as-grown crystal boule was divided into two growth regions [001] and [011]. The composition and the electrical properties of samples of the two regions were characterized in detail along the growth direction in the whole crystal boule. The PT content of [001]-grown samples increased from 27.7 to 36.8 mol. % along the growth direction, especially they are averagely higher about 0.7 mol. % than those of [011]-grown samples at the same growth position. The PMN content of [001]-grown samples decreased from 43.0 to 34.8 mol. %, which is lower than that of the corresponding [011]-grown samples. The compositional segregation behavior along [001] and [011] growth directions was discussed based on the crystal growth theories. Variations in the rhombohedral to tetragonal phase transition temperature (TRT), the piezoelectric properties, the coercive electric field and the remnant polarization of [001] samples were discussed according to changes in compositional segregation and crystal anisotropy. Under the exact same growth conditions, the [011]-grown crystal has a larger composition segregation effect than that of the [001]-grown crystal. This result provides a positive effect on analysing the nature and reducing the effect of compositional segregation.

Facile solvothermal fabrication of Pt47Ni53 nanopolyhedrons for greatly boosting electrocatalytic performances for oxygen reduction and hydrogen evolution

Pt-based bimetallic nanostructures with low content of Pt were considered as one of the attractive nanocatalysts for their high Pt utilization efficiency, remarkable catalytic characters and cost-effectiveness in facilitating the sluggish cathodic reactions in fuel cells. Herein, three-dimensional Pt47Ni53 nanopolyhedrons (NPHs) with abundant active sites were constructed by a facile one-pot solvothermal strategy, in which cytosine and cetyltrimethylammonium chloride (CTAC) worked as the co-structure directing agents. The Pt47Ni53 NPHs were mainly characterized by a series of techniques, showing the high catalytic activity and stability towards oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) in comparison to Pt13Ni87 nanocrystals (NCs), Pt63Ni37 NCs, commercial Pt black and/or Pt/C catalysts. Impressively, the mass activity of Pt47Ni53 NPHs was about 215.80 mA mgPt−1 for ORR, approximately 4-time increase relative to Pt black (49.60 mA mgPt−1). These results demonstrate the promising applications of the synthesized nanocatalysts in energy storage and transformation.

Combined effect of Pt and W alloying elements on Ni-silicide formation

A combinatorial study of the combined effect of Pt and W on Ni silicide formation is performed. Ni(Pt, W) films with thickness and composition gradients were prepared by a co-deposition composition spread technique using sputtering deposition from Pt, W, and Ni targets. The deposited Ni(Pt,W) films were characterized by X-ray diffraction, X-ray reflectivity, Rutherford backscattering, and atom probe tomography. The maximum content of alloying elements is close to 27 at. %. Simulations of the thickness and composition were carried out and compared with experimental results. In situ X-ray diffraction and atom probe tomography were used to study the phase formation. Both additive alloying elements (Pt + W) slow down the Ni consumption and the effect of W is more pronounced than the one of Pt. Regarding the effect of alloying elements on Ni silicides formation, three regions could be distinguished in the Ni(Pt,W)/Si wafer. For the region close to the Ni target, the low contents of alloying elements (Pt + W) have little impact on the phase sequence (δ-Ni2Si is the first silicide and NiSi forms when Ni is entirely consumed) but the kinetics of silicide formation slows down. The region close to the Pt target has high contents of (Pt + W) and is rich in Pt and a simultaneous phase formation of δ-Ni2Si and NiSi is observed. For the high (Pt + W) contents and W-rich region, NiSi forms unexpectedly before δ-Ni2Si and the subsequent growth of δ-Ni2Si is accompanied by the NiSi consumption. When Ni is entirely consumed, NiSi regrows at the expense of δ-Ni2Si.

Oxygen reduction reaction on Pt-Pd catalysts supported on carbon xerogels: Effect of the synthesis method

In this work, Pt-Pd nanoparticles supported on carbon xerogels (Pt-Pd/CX) were synthesised employing unusual routes, in order to evaluate its activity toward the oxygen reduction reaction (ORR). The synthesis methods produced materials with the planned composition (metal content close to 40 wt % and Pt:Pd atomic ratios around 1:2), with Pt, Pd and alloyed Pt-Pd nanoparticles well dispersed on the carbon support. The content of Pt in the nanoparticles was optimised through these procedures, placing this metal at the surface. As a consequence, the Pt-Pd/CX catalysts displayed high activity toward the ORR and remarkable resistance to corrosion, overcoming the electrocatalytic properties of a commercial Pt/C catalyst. Moreover, these catalysts involve four electrons in the ORR. Therefore, the study here presented indicated that the as-synthesised Pt-Pd/CX catalysts are suitable candidates to be employed as cathodes in proton exchange membrane fuel cells.