Supported Platinum Nanoparticles Research Articles

Core-shell structured Pt-transition metals nanoparticles supported on activated carbon for direct methanol fuel cells

Carbon supported platinum nanoparticles are commonly used as anode catalysts in low temperature fuel cells. Platinum exhibits an enhanced activity towards hydrogen oxidation reaction; however, its performance during low molecular weight alcohols oxidation is poor. Accordingly, this work presents a trial to improve the electrocatalytic performance of platinum-based electrocatalysts by developing core-shell structured M@Pt [M = Zn, Mn or Sn] nanoparticles supported on activated Vulcan XC-72R carbon black [M@Pt/AC]. They were fabricated using ethylene glycol as a reducing agent with the aid of microwave irradiation. The electrocatalytic activity of different M@Pt/AC electrocatalysts for oxidizing methanol molecules in 0.5 M H2SO4 solution was investigated using cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. These prepared nanomaterials displayed enhanced electrocatalytic behavior towards methanol oxidation reaction. The alcohol oxidation current density was arranged in an ascending order as: Zn@Pt/AC < Mn@Pt/AC < Sn@Pt/AC. Enhanced stability and charge transfer characteristics were also gained at these electrocatalysts especially Sn@Pt/AC to recommend its wide application as an efficient anode material in fuel cells.

Acceptorless Dehydrogenative Synthesis of Pyrimidines from Alcohols and Amidines Catalyzed by Supported Platinum Nanoparticles

A one-pot, acceptorless dehydrogenative method, using a carbon-supported Pt catalyst (Pt/C) along with KOtBu, has been developed for the synthesis of 2,4,6-trisubstituted pyrimidines from secondary and primary alcohols, and amidines. The reaction takes place efficiently using a wide range of substrate scopes (32 examples with isolated yields up to 92%). The Pt/C catalyst that promotes this process is reusable and has a higher turnover number (TON) than those employed in previously reported methods. The results of mechanistic studies suggest that the process takes place through a pathway that begins with Pt-catalyzed acceptorless dehydrogenation of the alcohol substrate, which is followed by sequential condensation, cyclization, and dehydrogenation. Measurements of the turnover frequency combined with the results of density functional theory calculations on different metal surfaces suggest that the adsorption energy of H on the Pt surface is optimal for the acceptorless dehydrogenation process, which cause...

The effect of amine functionalized carbon nanotubes as promising support for platinum nanoparticles on oxygen reduction reaction

In this study, multiwall carbon nanotubes (MWCNTs) were chemically oxidized (OMWCNTs) and functionalized with ethylenediamine (EDAMWCNTs) and diethylenetriamine (DETAMWCNTs) as amine precursors. The electrocatalysts were prepared through deposition of Pt nanoparticles on the functionalized MWCNTs by polyol method. The average size of Pt nanoparticles was found to lie between 4 and 5 nm. Cyclic Voltammetry (CV), Rotating Disk Electrode (RDE), Electrochemical Impedance Spectroscopy (EIS), and Chronoamperometry (CA) were employed to evaluate the electrochemical properties of the electrocatalysts. The Electrochemical active surface area (EASA), number of electron transferred (n), and onset potential for EDAMWCNTs and DETAMWCNTs were found to be about 32.2 and 45.8 (m2/g Pt), 4.03 and 4.10 (electron per oxygen molecule), and 0.986 and 0.997 (V vs RHE), respectively. However, in the case of Pt-OMWCNTs the above mentioned electrochemical characteristics were calculated to be 24.2 (m2/g Pt), 3.34 (electron per oxygen molecule), and 0.824 (V vs RHE), respectively. Moreover, EIS and CA indicate that introducing amine functional groups lead to less electron transfer resistance and better electrocatalytic activity and stability during oxygen reduction. The results show that the higher number of nitrogen atoms within the amine functional groups the more enhanced electrocatalytic performance of Pt nanoparticles in ORR.

Photochemical Synthesis of Radiate Titanium Oxide Microrods Arrays Supporting Platinum Nanoparticles for Photoassisted Electrooxidation of Methanol

AbstractPhotoassisted catalysis is recently adopted to accelerate the kinetics of the methanol oxidation, which allows the photocatalysis and electrocatalysis simultaneously occur on the catalyst surface and even on interior region. The rational design of highly efficient photoassisted electrocatalysts is highly desirable, however, it is very challenging. In this study, architectures of radiate TiO2 microrods arrays support Pt nanoparticles (Pt NPs/TiO2 MRs) are developed, via the combination of first hydrothermal and subsequent photodeposition process. Benefited from the synergetic effect of photocatalytic acceleration and the radiate architectures, the mass activity of Pt NPs/TiO2 MRs for methanol electrooxidation, under UV irradiation (wavelength: 365 nm), is 2.77 and 6.1 times as high as those of Pt NPs/TiO2 MRs without irradiation and commercial Pt/C, respectively. Moreover, under UV irradiation, both the CO tolerance and durability of the Pt NPs/TiO2 MRs catalysts are significantly improved. Notably, in both acidic and alkaline media, the Pt NPs/TiO2 MRs catalysts show improved electrocatalytic performance for photoassisted electrooxidation of methanol. This study provides a building art toward 3D architectures of radiate semiconductor MRs arrays supporting metallic NPs, and offers an effective way to improve the electrochemical activity of methanol oxidation utilizing the synergistic combination of photocatalysis and electrocatalysis.

Synthesis Via Beta-Cyclodextrin of Graphene Supported Platinum Nanoparticles for Application in a Hydrogen Evolution Reaction

Carbon-based fuels are currently being consumed at an unsustainable rate.1 The increase in energy consumption of the modern world has created a demand for alternative fuel sources, and the need has never been greater.2 With mounting economic and environmental concerns, the time for the switch to a clean, reliable alternative is prime. Hydrogen gas is a popular choice due to its low greenhouse gas emissions however, pure hydrogen gas is problematic due to its high flammability. Hydrogen feedstock materials are currently being explored due to their ability to store substantial amounts of hydrogen gas in a stable and safe way.2-3 NaBH4 is a common hydrogen feedstock material because of its high percentage of hydrogen (over 10% by weight). This reaction occurs very slowly without catalytic assistance.4 Transition metal catalysts have demonstrated efficiency in the oxidation of sodium borohydride resulting in an increased release rate of hydrogen gas.4 Platinum nanoparticles have demonstrated potential as a catalyst for this reaction. Nanoparticles must be stabilized on a support system for them to achieve maximum catalytic efficiency through reduced agglomeration and by maintaining the particle shape and size distribution.2-4 Graphene and graphene oxide scaffolds may be used as a support system for platinum nanoparticles in this reaction.5 Overall, platinum nanoparticles showed the highest reaction rate of 0.0022 mol-1 sec-1 with a standard concentration of NaBH4, at a pH of 7 subjected to an increased temperature at 30°C. References Retnamma, R.; Novais, A.Q.; Rangel, C.M. Kinetics of hydrolysis of sodium borohydride for hydrogen production in fuel cell applications: a review. Int J Hydrogen Energy 2011, 36, 9772-9790.Huff, C.; Long, J.; Aboulatta, A.; Heyman, A.; T. Abdel-Fattah, Silver Nanoparticle/Multi-Walled Carbon Nanotube Composite as Catalyst for Hydrogen Production. ECS J Solid State Sci Technol. 2017, 6, M115-118.Tian, Z. Q.; Jiang, S. P.; Liang, Y. M.; Shen, P. K. Synthesis and Characterization of Platinum Catalysts on Multiwalled Carbon Nanotubes by Intermittent Microwave Irradiation for Fuel Cell Applications. The Journal of Physical Chemistry B 2006, 110(11), 5343–5350.Pena-Alonsa R, Sicurelli A, Callone E, Carturan G, Raj R. A picoscale catalyst for hydrogen generation from NaBH4 for fuel cells. J Power Sources 2007; 165:315-23.Kochkar, H., Aouine, Ghorbel, A.,Berhault, G. Shape-Controlled Synthesis of Silver and Palladium Nanoparticles Using β-Cyclodextrin. Journal of Physical Chemistry 2011, 115, 11364-11373.

Graphene aerogel supported platinum nanoparticles for formic acid electro-oxidation

The performance of the direct formic acid fuel cell largely depends on the quality of the electrocatalysts used in the fuel cells. New materials are of great interest in order to improve the activity and stability of the electrocatalyst used in formic acid electro-oxidation for better direct formic acid fuel cell performance. In this study, different support materials including synthesized graphene aerogel (GA), commercial carbon black (C) or their hybrids(GA/C) were used. Platinum (Pt) nanoparticles were decorated on the defect sites of these materials by using microwave irradiation in order to improve the catalytic activity for formic acid electro-oxidation in acidic media. GA/C hybrid supports are synthesized via simple liquid mechanical mixing approach (GA/C(1)) and through hydrothermal process (GA/C(2)). Synthesized catalysts were called Pt/C, Pt/GA and Pt/GA/C(1) and Pt/GA/C(2). The as-prepared catalysts were characterized with SEM, TEM, XRD and ICP-MS. The SEM results show that GA has a 3D macroporous structure. Electrochemical measurements tests showed that either GA or GA/C material is promising support materials for Pt nanoparticles towards formic acid electro-oxidaiton. The electrochemical test results revealed that the support material affect the activity. Synthesized GA supported catalysts gave better activity than synthesized commercial carbon supported catalyst for oxidation of formic acid. Pt/GA and Pt/GA/C(2) catalysts showed higher tolerance against the poisoning effect of CO and direct pathway dominated the electro-oxidation of formic acid.

Synthesis, characterization and comparison of polythiophene–carbon nanocomposite materials as Pt electrocatalyst supports for fuel cell applications

A novel polymer–carbon (PTh–C) nanocomposites containing different percentages of polythiophene (10, 20 and 50% (w/w)) and carbon (Vulcan XC-72) was prepared by a facile solution dispersion method and used to support platinum nanoparticles. The effect of using different percentages of polythiophene in nanocomposites and subsequently prepared electrocatalysts was investigated. The resultant electrocatalysts were extensively characterized by physical (X-ray diffraction (XRD) and transmission electron microscopy (TEM)) and electrochemical (cyclic voltammetry (CV)) techniques. The TEM results showed that the fine Pt nanoparticles prepared by ethylene glycol (EG) method were distributed on the surface of the 50% PTh–C nanocomposites successfully. From the XRD patterns, the average size of dispersed Pt nanoparticles with the face-centered cubic (fcc) structure on 50% PTh–C, 20% PTh–C, 10% PTh–C and carbon were about 4.9, 5.2, 5.4 and 6.1 nm, respectively. The conductivity of PTh–C with different percentages of pure PTh was compared with the conductivity of the corresponding support of pure PTh. It is observed that the conductivity of 50% PTh–C nanocomposites is about 600 times higher than that of pure PTh. Finally, CV measurements of hydrogen and methanol oxidations indicated that Pt/50% PTh–C had a higher electrochemical surface area and higher catalytic activity for methanol oxidation reaction compared to other electrocatalysts. These measurements showed that the Pt/50% PTh–C electrocatalyst by the value of 3.85 had higher \(I_{\mathrm{f}}/I_{\mathrm{b}}\) ratio with respect to Pt/10% PTh–C and Pt/20% PTh–C by the values of 2.66 and 2.0, respectively.

Turning Biodiesel Waste Glycerol into 1,3-Propanediol: Catalytic Performance of Sulphuric acid-Activated Montmorillonite Supported Platinum Catalysts in Glycerol Hydrogenolysis

Direct C-O hydrogenolysis of bioglycerine to produce 1,3-propanediol selectively is a vital technology that can expand the scope of biodiesel industry and green chemical production from biomass. Herein we report sulphuric acid-activated montmorillonite clay supported platinum nanoparticles as highly effective solid acid catalysts for the selective production of 1,3-propanediol from glycerol. The catalytic performances of the catalysts were investigated in the hydrogenolysis of glycerol with a fixed bed reactor under ambient pressure. The results were found promising and showed that the activation of montmorillonite by sulphuric acid incorporated Brønsted acidity in the catalyst and significantly improved the selectivity to 1,3-propanediol. The catalytic performance of different platinum loaded catalysts was examined and 2 wt% Pt/S-MMT catalyst presented superior activity among others validating 62% 1,3-propanediol selectivity at 94% glycerol conversion. The catalytic activity of 2Pt/S-MMT was systematically investigated under varying reaction parameters including reaction temperature, hydrogen flow rate, glycerol concentration, weight hourly space velocity, and contact time to derive the optimum conditions for the reaction. The catalyst stability, reusability and structure-activity correlation were also elucidated. The high performance of the catalyst could be ascribed to well disperse Pt nanoparticles immobilized on acid-activated montmorillonite, wider pore-structure and appropriate acid sites of the catalyst.

Layered Pt.ZSM-5-C by Greener Chemical Reduction for Catalysing Fuel Cell Reactions

Metal ion exchanged catalysts are known now and are successfully used for many catalytic processes. But supported metal nanoparticles on the zeolite bed, and their use as catalysts is still under experimental probe. ZSM-5 supported platinum nanoparticles are synthesized from in-situ chemical reduction of platinum chloride solution in the presence of zeolite, by zinc dust chemical reduction method which is comparatively ‘greener’. This platinum nanoparticle loaded ZSM-5 is studied in the role of catalyst in electrooxidation of methanol and ethanol using Nafion-117 to bind the catalyst on carbon felt. The platinum nanoparticle loaded ZSM-5 is found to be a better catalyst compared to pure ZSM-5 and pure platinum. This greener chemical reduction method can be used as the results show that zeolite modified catalysts are as good as those prepared by other less environment friendly methods, if not better.

Understanding the Stability and Surface Restructuring of Platinum in an Electrochemical Environment

Platinum is a commonly used catalyst in aqueous environments, particularly in fuel cells as an electrocatalyst for hydrogen oxidation [1] and oxygen reduction [2]. To maximize the activity per unit mass (and per unit cost), the electrocatalyst is typically dispersed as small Pt nanoparticles. These nanoparticles may change in size and shape during use in an electrochemical environment due to dissolution/deposition, oxide growth/reduction, and reconstruction [3]. The resulting size and shape of the nanoparticles are dictated in part by the surface energy of the various platinum surface facets. Additionally, many techniques exist to synthesize Pt nanoparticles in an aqueous electrochemical environment, where again the relative stability of the platinum facets is plays a role in controlling the size and shape of the resulting Pt nanoparticles. To understand the driving forces for surface faceting and reconstruction, we have previously used density functional theory to calculate the surface energy of Pt(111), Pt(100), and Pt(110) in an aqueous environment as a function of potential, including the adsorption of hydrogen, hydroxide, and oxygen, spanning the full electrochemical window of water [4]. While the Pt(111) surface is the most stable facet in vacuum, we found the strong binding of hydrogen to Pt(100) and hydroxide/oxygen to Pt(110) drives these surfaces to be more stable at low and high potentials, respectively [4]. We use these relative surface energies to explain the experimentally observed growth in the fraction of 110 step sites seen on cycling a Pt(111) single crystal electrode to high potentials into the oxide formation region, where the 110 sites are most stable at potentials where this oxide is reduced [5]. Further, the strong adsorption of hydrogen to Pt(100) at low potentials may explain the growth of 100 sites (and formation of tetrahexahedral nanoparticles) seen on square wave cycling of spherical Pt nanoparticles [6,7]. We have recently extended this work to include stepped surfaces (Pt(553), Pt(533), and Pt(110) 1x2), as well as to examine high coverages of hydrogen (> 1ML) adsorbed at low potentials, where sub-surface hydrogen may drive surface reconstruction and the appearance of the anomalous “third peak¨ seen in cyclic voltammograms measured on platinum.[1] H. A. Gasteiger, J. E. Panels, and S. G. Yan, "Dependence of PEM fuel cell performance on catalyst loading," Journal of Power Sources, vol. 127, pp. 162-171, 2004.[2] H. A. Gasteiger, S. S. Kocha, B. Sompalli, and F. T. Wagner, "Activity benchmarks and requirements for Pt, Pt-alloy, and non-Pt oxygen reduction catalysts for PEMFCs," Applied Catalysis B: Environmental, vol. 56, pp. 9-35, 2005.[3] Y. Shao-Horn, W.C. Sheng, S. Chen, P.J. Ferreira, E.F. Holby, D. Morgan, “Instability of supported platinum nanoparticles in low-temperature fuel cells,” Top. Catal., vol. 46, pp. 285-305, 2007.[4] I. T. McCrum, M. A. Hickner, and M. J. Janik, “First-principles calculation of Pt surface energies in an electrochemical environment: thermodynamic driving forces for surface faceting and nanoparticle reconstruction,” Langmuir, vol 33, pp. 7043-7052, 2017.

One-Pot Synthesis of Pt@TiO2 Electrocatalysts for Methanol Oxidation

Conducting metal@metal oxide structures are promising materials to overcome the limitations of state-of-the-art fuel cell catalysts based on carbon as support material, which suffer from carbon corrosion and metal nanoparticle sintering. One interesting metal oxide is titanium oxide, which shows high stability under fuel cell operating conditions [1-3]. Also due to electronic effects the catalytic properties of supported platinum nanoparticles can be tuned by metal oxide supports, leading to increased catalytic activity or better poisoning tolerance, which are the main research goals for methanol oxidation catalysts [4,5]. In this work, the one-pot synthesis of Pt@TiO2 nanostructures is presented. The synthesis is based on hydrophobic nanoreactor templating, using inverse block copolymer micelles as nanoreactor templates, allowing the concomitant structuration of the metal and metal oxide components respectively [6-8]. For the synthesis of platinum nanoparticles supported on titanium oxide, both metal and metal oxide precursor are loaded into the micelles. The micellar template is removed after solvent evaporation by calcination under air, leading, after a subsequent reduction step, to nanostructured composites made of finely distributed 2-4 nm platinum nanoparticles supported on titanium oxide particles. The overall size and shape of the Pt@TiO2 nanocomposite particles is thereby imprinted by the size and shape of the micellar template. Variation of the calcination temperature revealed that the number and size of the platinum nanoparticles can be controlled by the calcination temperature as well as the crystallinity of the oxide support. Using this approach thin film electrodes were made by dipcoating monolayers of Pt@TiO2 nanocomposites on ITO coated glass substrates as model electrocatalysts to study the catalytic properties of the Pt@TiO2 nanostructures regarding methanol oxidation. Cyclic voltammetry revealed a classical platinum CV, proving the electrochemical accessibility of the platinum nanoparticles. After the addition of methanol the Pt@TiO2 catalysts showed high specific activities, reaching values of up to 2 mA/cm²Pt (anodic peak current density) for the catalysts calcined at 500 °C. Compared to a commercial Pt/C catalyst (20wt.% Pt on Vulcan XC72), the specific activity increased by a factor of 2. The second oxidation peak in the cathodic scan direction, which is usually attributed to the oxidation of intermediates from the methanol oxidation, was used to characterize the poisoning tolerance of the catalysts by calculating the ratio of the peak currents from forward and backward scan (If /Ib ). In case of the Pt@TiO2 catalysts the I f/I b values are around 1.5, which is comparable to other Pt@metal oxide catalysts reported in literature [4,5]. In case of the commercial Pt/C catalyst the I f/I b value is 0.7, demonstrating the higher poisoning tolerance of the Pt@TiO2 catalyst. These results demonstrate that Pt@TiO2 is a promising electrocatalyst for methanol oxidation. The presented one-pot approach allows an easy synthesis of supported noble metal catalysts with full control over activity determining parameters like noble metal loading, nanoparticle size and composition.

Low-temperature synthesis of nitrogen doped carbon nanotubes as promising catalyst support for methanol oxidation

Abstract The electrochemical methanol oxidation reaction (MOR) is of paramount importance for direct methanol fuel cell (DMFC) application, where efficient catalysts are required to facilitate the complicated multiple charge transfer process. The catalyst support not only determines the dispersion status of the catalysts particles, but also exerts great influence on the electronic structure of the catalysts, thereby altering its intrinsic activity. Herein, we demonstrated that nitrogen atoms, assisted by the pre-treatment of carbon matrix with oxidants, can be easily doped into carbon nanotubes at low temperature. The obtained nitrogen-doped carbon nanotubes can effectively improve the dispersion of the supported platinum nanoparticles and facilitate the MOR by modifying the electronic structure of platinum atoms, through catalyst-support interaction.

Physicochemical Properties of Nanoparticles: Interaction of Supported Platinum Nanoparticles with Gaseous Reactants

The shapes, sizes, and electronic structures of platinum nanoparticles supported onto highly oriented pyrolytic graphite and oxidized silicon by different methods and their adsorptive properties with respect to hydrogen, oxygen, water, and ammonia were established. The apparent activation energy of the reduction of single oxidized platinum nanoparticles with molecular hydrogen was determined. The possibility of controlling the rate of ammonia decomposition by a nanostructured platinum coating by the application of electric potentials of different values and polarities to it was demonstrated.

Graphene Supported Platinum Nanoparticles Modified Electrode and Its Enzymatic Biosensing for Lactic Acid

Lactic acid is a metabolic product of human physiological activity. It is of great importance in the diagnosis and treatment of diseases and scientific sports management. It is necessary to build a lactate biosensor that can realize rapid and accurate detection of lactic acid. Graphene supported platinum nanoparticles (GPNs) were prepared by the redox reaction between graphene oxide, chloroplatinic acid and ethylene glycol. Pt nanoparticles were highly dispersed on the graphene, and the surface platinum content of the prepared GPNs was as high as 28%. The GPNs showed excellent electrochemical performance compared to graphene modified electrodes or platinum modified electrodes. An enzymatic lactic acid biosensor (ELB) was prepared by immobilizing lactate oxidase (LOx) on the GPNs modified glassy carbon electrode. The response current of the sensor at +0.4 V in the presence of lactic acid showed a wide linear relationship in the range of 0–1.0 mM, and the limit of detection (LOD) was calculated to be 8.0 μM according to S/N = 3. The ELB was free from common interfering species, and exhibited excellent stability. From the 1st day to the 15th day, the response signal lost less than 2%.

Experimental Protocol for HOR and ORR in Alkaline Electrochemical Measurements

This work revises the essentials of electrocatalytic electrochemical measurement done in alkaline electrolytes. The hydrogen oxidation reaction (HOR) and the oxygen reduction reaction (ORR) were considered as a baseline to understand some key critical factors in a half-cell system. The material considered herein was essentially the carbon supported platinum nanoparticles as benchmark material. The main electrochemical techniques considered were cyclic voltammetry (CV) and the rotating disk electrode (RDE). The critical factors considered were the electrochemical cell vessel, reference electrode, nature of the cation in the alkaline electrolyte, and ohmic drop correction.

Application of graphene supporting platinum nanoparticles layer in electrochemical sensors with potentiometric and voltammetric detection

The present work reports a possibility of using a layer made of graphene supporting platinum nanoparticles (PtNPs-GR) in electrochemical sensors as active and intermediate layer. New sensors with greatly improved both potentiometric and voltammetric signals were prepared by using a simple and effective drop casting method and characterized by a cyclic voltammetry and a electrochemical impedance spectroscopy. The performance of the new potentiometric sensor was evaluated by the use an ion-selective membrane with well-known valinomycin ion carrier. Potassium electrodes had a Nernstian slope (59.10 mV/pK), high stability and reproducibility of the standard potential values, and a very small drift potential. Under optimized operating conditions, the voltammetric sensor with PtNPs-GR responded to paracetamol concentration in the range from 20 nM to 2.2 μM with the detection limit of 8 nM.

Selective Conversion of Renewable Furfural with Ethanol to Produce Furan-2-acrolein Mediated by Pt@MOF-5

The selective conversion of furfural (FUR) with ethanol to produce furan-2-acrolein has been successfully performed in the presence of O2, in which metal organic framework (MOF) supported platinum nanoparticles (Pt@MOF-5, Pt@UIO-66, and Pt@UIO-66-NH2) were used as the catalysts. Under the optimal conditions, 84.1% conversion of FUR and 90.1% selectivity of furan-2-acrolein was obtained with Pt@MOF-5 as the catalyst. Moreover, the catalysts were characterized by XRD, H2-TPR, HRTEM, HRSEM, and XPS techniques, with the synergetic effect of well-dispersed platinum nanoparticles in the MOF-5 channel. In addition, the results of the recycling experiment exhibited that there was no significant loss after the catalyst was reused 5 times.

Pt Nanoparticles Supported on Mesoporous CeO2 Nanostructures Obtained through Green Approach for Efficient Catalytic Performance toward Ethanol Electro-oxidation

In this report, an easy and green approach to the synthesis of mesoporous cerium oxide (CeO2) nanostructures and followed by supporting platinum nanoparticles (NPs) on CeO2 nanostructures (Pt/CeO2) and their application as versatile electrocatalysts for ethanol electrooxidation has been established. The synthesis of mesoporous Pt/CeO2 nanostructures involves two steps. First, mesoporous CeO2 nanostructures were synthesized via macroalgae polymer mediated approach and followed by supporting of PtNPs of ca. 5–10 nm over the mesoporous CeO2 nanostructures using seed-mediated chemical reduction process. The structural and spectroscopic characterization techniques such as transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman, X-ray photoelectron spectroscopy (XPS), and small-angle X-ray scattering (SAXS) studies confirm the strong coupling between PtNPs and the mesoporous CeO2 support resulting in the generation of more oxygen vacancies, which can facilitate the enhanced charge transport at th...

Platinum nanoparticles encapsulated in nitrogen-doped graphene quantum dots: Enhanced electrocatalytic reduction of oxygen by nitrogen dopants

Nitrogen-doped graphene quantum dots (NGQDs) prepared by hydrothermal treatment of citric acid and urea were used as an effective support for platinum nanoparticles synthesized by carbon monoxide reduction of Pt(IV) in water. TEM measurements showed that the platinum nanoparticles were 2.03 ± 0.43 nm in diameter, and wrapped with one layer of NGQDs, as compared to results from AFM measurements. XPS measurements confirmed the formation of metallic platinum and the incorporation of nitrogen dopants within the graphitic molecular skeleton, and the shifts of Pt 4f binding energy suggested that charge transfer from Pt to NGQDs was facilitated by the more electronegative nitrogen dopants, as compared to platinum nanoparticle supported on undoped GQDs (Pt-GQDs). Because of this, the Pt-NGQDs nanocomposites showed markedly enhanced catalytic activity towards oxygen reduction reactions in alkaline media, as compared to Pt-GQDs, with a specific activity more than three times that of commercial Pt/C. Further comparison with NGQDs-supported gold nanoparticles showed that the platinum nanoparticles, rather than the NGQDs, played a dominant role in determining the ORR activity.

TixCe(1-x)O2 as Pt support for the PROX reaction: Effect of the solvothermal synthesis

TiCe mixed oxides with different Ti/Ce atomic ratios have been synthesized via a solvothermal method and used as supports for platinum nanoparticles. These catalysts were tested in the preferential oxidation of CO in excess of H2 (PROX reaction) using different feed compositions in order to simulate real conditions. Both, supports and catalysts, were characterized by a wide variety of techniques including N2 adsorption, XRF, XRD, Raman spectroscopy, XPS, H2-TPR, UV–Vis and DRIFTS. The best performance was obtained with the Pt/Ti0.9Ce0.1O2 catalyst, what was attributed to the incorporation of Ce atoms in the TiO2 lattice. 10% at. Ce is the maximum concentration we could incorporate in the TiO2 lattice by using the solvothermal method.