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Catalysts, Volume 5, Issue 3 (September 2015), Pages 1003-1635

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Open AccessArticle Electrocatalytic Activity and Durability of Pt-Decorated Non-Covalently Functionalized Graphitic Structures
Catalysts 2015, 5(3), 1622-1635; https://doi.org/10.3390/catal5031622
Received: 26 May 2015 / Revised: 7 September 2015 / Accepted: 11 September 2015 / Published: 21 September 2015
Cited by 7 | PDF Full-text (1270 KB) | HTML Full-text | XML Full-text
Abstract
Carbon graphitic structures that differ in morphology, graphiticity and specific surface area were used as support for platinum for Oxygen Reduction Reaction (ORR) in low temperature fuel cells. Graphitic supports were first non-covalently functionalized with pyrene carboxylic acid (PCA) and, subsequently, platinum nanoparticles
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Carbon graphitic structures that differ in morphology, graphiticity and specific surface area were used as support for platinum for Oxygen Reduction Reaction (ORR) in low temperature fuel cells. Graphitic supports were first non-covalently functionalized with pyrene carboxylic acid (PCA) and, subsequently, platinum nanoparticles were nucleated on the surface following procedures found in previous studies. Non-covalent functionalization has been proven to be advantageous because it allows for a better control of particle size and monodispersity, it prevents particle agglomeration since particles are bonded to the surface, and it does not affect the chemical and physical resistance of the support. Synthesized electrocatalysts were characterized by electrochemical half-cell studies, in order to evaluate the Electrochemically Active Surface Area (ECSA), ORR activity, and durability to potential cycling and corrosion resistance. Full article
(This article belongs to the Special Issue Electrocatalysis in Fuel Cells) Printed Edition available
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Open AccessArticle Investigation of Room Temperature Synthesis of Titanium Dioxide Nanoclusters Dispersed on Cubic MCM-48 Mesoporous Materials
Catalysts 2015, 5(3), 1603-1621; https://doi.org/10.3390/catal5031603
Received: 2 August 2015 / Revised: 1 September 2015 / Accepted: 11 September 2015 / Published: 18 September 2015
Cited by 3 | PDF Full-text (389 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Titania containing cubic MCM-48 mesoporous materials were synthesized successfully at room temperature by a modified Stöber method. The integrity of the cubic mesoporous phase was retained even at relatively high loadings of titania. The TiO2-MCM-48 materials were extensively characterized by a
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Titania containing cubic MCM-48 mesoporous materials were synthesized successfully at room temperature by a modified Stöber method. The integrity of the cubic mesoporous phase was retained even at relatively high loadings of titania. The TiO2-MCM-48 materials were extensively characterized by a variety of physico-chemical techniques. The physico-chemical characterization indicate that Ti4+ ions can be substituted in framework tetrahedral positions. The relative amount of Ti4+ ions in tetrahedral position was dependent on the order of addition of the precursor. Even at relatively high loadings of titania, no distinct bulk phase of titania could be observed indicating that the titania nanoclusters are well dispersed on the high surface area mesoporous material and probably exist as amorphous nanoclusters. The TiO2-MCM-48 materials were found to exhibit 100% selectivity in the cyclohexene oxidation at room temperature in the presence of tert-butylhydroperoxide (t-BHP) as the oxidant. The results suggest that room temperature synthesis is an attractive option for the preparation of TiO2-MCM-48 materials with interesting catalytic properties. Full article
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Open AccessReview Nitrogen-Doped Carbon Nanotube and Graphene Materials for Oxygen Reduction Reactions
Catalysts 2015, 5(3), 1574-1602; https://doi.org/10.3390/catal5031574
Received: 28 May 2015 / Revised: 13 August 2015 / Accepted: 1 September 2015 / Published: 14 September 2015
Cited by 62 | PDF Full-text (2034 KB) | HTML Full-text | XML Full-text
Abstract
Nitrogen-doped carbon materials, including nitrogen-doped carbon nanotubes (NCNTs) and nitrogen-doped graphene (NG), have attracted increasing attention for oxygen reduction reaction (ORR) in metal-air batteries and fuel cell applications, due to their optimal properties including excellent electronic conductivity, 4e transfer and superb mechanical
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Nitrogen-doped carbon materials, including nitrogen-doped carbon nanotubes (NCNTs) and nitrogen-doped graphene (NG), have attracted increasing attention for oxygen reduction reaction (ORR) in metal-air batteries and fuel cell applications, due to their optimal properties including excellent electronic conductivity, 4e transfer and superb mechanical properties. Here, the recent progress of NCNTs- and NG-based catalysts for ORR is reviewed. Firstly, the general preparation routes of these two N-doped carbon-allotropes are introduced briefly, and then a special emphasis is placed on the developments of both NCNTs and NG as promising metal-free catalysts and/or catalyst support materials for ORR. All these efficient ORR electrocatalysts feature a low cost, high durability and excellent performance, and are thus the key factors in accelerating the widespread commercialization of metal-air battery and fuel cell technologies. Full article
(This article belongs to the Special Issue Electrocatalysis in Fuel Cells) Printed Edition available
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Open AccessArticle Bismuth Molybdate Catalysts Prepared by Mild Hydrothermal Synthesis: Influence of pH on the Selective Oxidation of Propylene
Catalysts 2015, 5(3), 1554-1573; https://doi.org/10.3390/catal5031554
Received: 20 July 2015 / Accepted: 25 August 2015 / Published: 10 September 2015
Cited by 14 | PDF Full-text (962 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A series of bismuth molybdate catalysts with relatively high surface area was prepared via mild hydrothermal synthesis. Variation of the pH value and Bi/Mo ratio during the synthesis allowed tuning of the crystalline Bi-Mo oxide phases, as determined by X-ray diffraction (XRD) and
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A series of bismuth molybdate catalysts with relatively high surface area was prepared via mild hydrothermal synthesis. Variation of the pH value and Bi/Mo ratio during the synthesis allowed tuning of the crystalline Bi-Mo oxide phases, as determined by X-ray diffraction (XRD) and Raman spectroscopy. The pH value during synthesis had a strong influence on the catalytic performance. Synthesis using a Bi/Mo ratio of 1/1 at pH ≥ 6 resulted in γ-Bi2MoO6, which exhibited a better catalytic performance than phase mixtures obtained at lower pH values. However, a significantly lower catalytic activity was observed at pH = 9 due to the low specific surface area. γ-Bi2MoO6 synthesized with Bi/Mo = 1/1 at pH = 6 and 7 exhibited relatively high surface areas and the best catalytic performance. All samples prepared with Bi/Mo = 1/1, except samples synthesized at pH = 1 and 9, showed better catalytic performance than samples synthesized with Bi/Mo = 2/3 at pH = 4 and 9 and γ-Bi2MoO6 synthesized by co-precipitation at pH = 7. At temperatures above 440 °C, the catalytic activity of the hydrothermally synthesized bismuth molybdates started to decrease due to sintering and loss of surface area. These results support that a combination of the required bismuth molybdate phase and a high specific surface area is crucial for a good performance in the selective oxidation of propylene. Full article
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Open AccessArticle Use of a µ-Scale Synthetic Gas Bench for Direct Comparison of Urea-SCR and NH3-SCR Reactions over an Oxide Based Powdered Catalyst
Catalysts 2015, 5(3), 1535-1553; https://doi.org/10.3390/catal5031535
Received: 8 July 2015 / Revised: 25 August 2015 / Accepted: 28 August 2015 / Published: 4 September 2015
Cited by 4 | PDF Full-text (834 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The selective catalytic reduction (SCR) of NOx by NH3 has been extensively studied in the literature, mainly because of its high potential to remediate the pollution of diesel exhaust gases. The implementation of the NH3-SCR process into passenger cars
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The selective catalytic reduction (SCR) of NOx by NH3 has been extensively studied in the literature, mainly because of its high potential to remediate the pollution of diesel exhaust gases. The implementation of the NH3-SCR process into passenger cars requires the use of an ammonia precursor, provided by a urea aqueous solution in the conventional process. Although the thermal decomposition and hydrolysis mechanisms of urea are well documented in the literature, the influence of the direct use of urea on the NOx reduction over SCR catalysts may be problematic. With the aim to evaluate prototype powdered catalysts, a specific synthetic gas bench adjusted to powdered material was developed, allowing the use of NH3 or urea as reductant for direct comparison. The design of the experimental setup allows vaporization of liquid urea at 200 °C under 10 bar using an HPLC pump and a micro injector of 50 μm diameter. This work presents the experimental setup of the catalytic test and some remarkable catalytic results towards further development of new catalytic formulations specifically dedicated to urea-SCR. Indeed, a possible divergence in terms of DeNOx efficiency is evidenced depending on the nature of the reductant, NH3 or urea solution. Particularly, the evaluated catalyst may not allow an optimal NOx conversion because of a lack in ammonia availability when the urea residence time is shortened. This is attributed to insufficient activity of isocyanic acid (HNCO) hydrolysis, which can be improved by addition upstream of an active solid for the hydrolysis reaction such as ZrO2. Thus, this µ-scale synthetic gas bench adjusted to powdered materials enables the specific behaviour of urea use for NOx reduction to be demonstrated. Full article
(This article belongs to the Special Issue Automotive Emission Control Catalysts)
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Open AccessReview Recent Advances on Electro-Oxidation of Ethanol on Pt- and Pd-Based Catalysts: From Reaction Mechanisms to Catalytic Materials
Catalysts 2015, 5(3), 1507-1534; https://doi.org/10.3390/catal5031507
Received: 8 June 2015 / Revised: 13 August 2015 / Accepted: 13 August 2015 / Published: 2 September 2015
Cited by 69 | PDF Full-text (1421 KB) | HTML Full-text | XML Full-text
Abstract
The ethanol oxidation reaction (EOR) has drawn increasing interest in electrocatalysis and fuel cells by considering that ethanol as a biomass fuel has advantages of low toxicity, renewability, and a high theoretical energy density compared to methanol. Since EOR is a complex multiple-electron
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The ethanol oxidation reaction (EOR) has drawn increasing interest in electrocatalysis and fuel cells by considering that ethanol as a biomass fuel has advantages of low toxicity, renewability, and a high theoretical energy density compared to methanol. Since EOR is a complex multiple-electron process involving various intermediates and products, the mechanistic investigation as well as the rational design of electrocatalysts are challenging yet essential for the desired complete oxidation to CO2. This mini review is aimed at presenting an overview of the advances in the study of reaction mechanisms and electrocatalytic materials for EOR over the past two decades with a focus on Pt- and Pd-based catalysts. We start with discussion on the mechanistic understanding of EOR on Pt and Pd surfaces using selected publications as examples. Consensuses from the mechanistic studies are that sufficient active surface sites to facilitate the cleavage of the C–C bond and the adsorption of water or its residue are critical for obtaining a higher electro-oxidation activity. We then show how this understanding has been applied to achieve improved performance on various Pt- and Pd-based catalysts through optimizing electronic and bifunctional effects, as well as by tuning their surface composition and structure. Finally we point out the remaining key problems in the development of anode electrocatalysts for EOR. Full article
(This article belongs to the Special Issue Electrocatalysis in Fuel Cells) Printed Edition available
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Open AccessArticle TiO2-Impregnated Porous Silica Tube and Its Application for Compact Air- and Water-Purification Units
Catalysts 2015, 5(3), 1498-1506; https://doi.org/10.3390/catal5031498
Received: 24 June 2015 / Revised: 31 July 2015 / Accepted: 19 August 2015 / Published: 2 September 2015
Cited by 6 | PDF Full-text (618 KB) | HTML Full-text | XML Full-text
Abstract
A simple, convenient, reusable, and inexpensive air- and water-purification unit including a one-end sealed porous amorphous-silica (a-silica) tube coated with TiO2 photocatalyst layers has been developed. The porous a-silica layers were formed through outside vapor deposition (OVD). TiO2 photocatalyst layers were formed through
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A simple, convenient, reusable, and inexpensive air- and water-purification unit including a one-end sealed porous amorphous-silica (a-silica) tube coated with TiO2 photocatalyst layers has been developed. The porous a-silica layers were formed through outside vapor deposition (OVD). TiO2 photocatalyst layers were formed through impregnation and calcination onto a-silica layers. The resulting porous TiO2-impregnated a-silica tubes were evaluated for air-purification capacity using an acetaldehyde gas decomposition test. The tube (8.5 mm e.d. × 150 mm) demonstrated a 93% removal rate for high concentrations (ca. 300 ppm) of acetaldehyde gas at a single-pass condition with a 250 mL/min flow rate under UV irradiation. The tube also demonstrated a water purification capacity at a rate 2.0 times higher than a-silica tube without TiO2 impregnation. Therefore, the tubes have a great potential for developing compact and in-line VOC removal and water-purification units. Full article
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Open AccessArticle Removal of Toluene over NaX Zeolite Exchanged with Cu2+
Catalysts 2015, 5(3), 1479-1497; https://doi.org/10.3390/catal5031479
Received: 26 June 2015 / Revised: 20 July 2015 / Accepted: 24 July 2015 / Published: 2 September 2015
Cited by 20 | PDF Full-text (523 KB) | HTML Full-text | XML Full-text
Abstract
Toluene is a major air pollutant emitted from painting and metal coating processes and might have some health effects. Adsorption and catalytic complete oxidation are promising ways to retain or convert toluene into harmless products. The present work aims to develop a bifunctional
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Toluene is a major air pollutant emitted from painting and metal coating processes and might have some health effects. Adsorption and catalytic complete oxidation are promising ways to retain or convert toluene into harmless products. The present work aims to develop a bifunctional material which can be used as an adsorbent and catalyst for low-temperature toluene removal. Copper zeolites were obtained by exchanging the sodium in the parent NaX zeolite with copper from aqueous solutions of Cu(NO3)2∙2.5H2O. Several characterization techniques, H2-TPR, XPS, XRD and N2 physisorption, were used in order to evaluate the redox, surface, structural and textural properties of the materials, respectively. The various materials were tested in adsorption and catalytic processes. The sample with low copper content (1 wt. %) exhibited promising features in terms of toluene adsorption capacity and total oxidation. The results can be correlated to the presence of micropores and well-dispersed CuO species. Full article
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Open AccessReview Nanoscale Alloying in Electrocatalysts
Catalysts 2015, 5(3), 1465-1478; https://doi.org/10.3390/catal5031465
Received: 16 May 2015 / Revised: 23 July 2015 / Accepted: 5 August 2015 / Published: 19 August 2015
Cited by 2 | PDF Full-text (3896 KB) | HTML Full-text | XML Full-text
Abstract
In electrochemical energy conversion and storage, existing catalysts often contain a high percentage of noble metals such as Pt and Pd. In order to develop low-cost electrocatalysts, one of the effective strategies involves alloying noble metals with other transition metals. This strategy promises
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In electrochemical energy conversion and storage, existing catalysts often contain a high percentage of noble metals such as Pt and Pd. In order to develop low-cost electrocatalysts, one of the effective strategies involves alloying noble metals with other transition metals. This strategy promises not only significant reduction of noble metals but also the tunability for enhanced catalytic activity and stability in comparison with conventional catalysts. In this report, some of the recent approaches to developing alloy catalysts for electrocatalytic oxygen reduction reaction in fuel cells will be highlighted. Selected examples will be also discussed to highlight insights into the structural and electrocatalytic properties of nanoalloy catalysts, which have implications for the design of low-cost, active, and durable catalysts for electrochemical energy production and conversion reactions. Full article
(This article belongs to the Special Issue Electrocatalysis in Fuel Cells) Printed Edition available
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Open AccessReview Advances in Ceramic Supports for Polymer Electrolyte Fuel Cells
Catalysts 2015, 5(3), 1445-1464; https://doi.org/10.3390/catal5031445
Received: 29 June 2015 / Revised: 2 August 2015 / Accepted: 6 August 2015 / Published: 17 August 2015
Cited by 19 | PDF Full-text (897 KB) | HTML Full-text | XML Full-text
Abstract
Durability of catalyst supports is a technical barrier for both stationary and transportation applications of polymer-electrolyte-membrane fuel cells. New classes of non-carbon-based materials were developed in order to overcome the current limitations of the state-of-the-art carbon supports. Some of these materials are designed
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Durability of catalyst supports is a technical barrier for both stationary and transportation applications of polymer-electrolyte-membrane fuel cells. New classes of non-carbon-based materials were developed in order to overcome the current limitations of the state-of-the-art carbon supports. Some of these materials are designed and tested to exceed the US DOE lifetime goals of 5000 or 40,000 hrs for transportation and stationary applications, respectively. In addition to their increased durability, the interactions between some new support materials and metal catalysts such as Pt result in increased catalyst activity. In this review, we will cover the latest studies conducted with ceramic supports based on carbides, oxides, nitrides, borides, and some composite materials. Full article
(This article belongs to the Special Issue Electrocatalysis in Fuel Cells) Printed Edition available
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Open AccessArticle Dimethyl-Aluminium Complexes Bearing Naphthyl-Substituted Pyridine-Alkylamides as Pro-Initiators for the Efficient ROP of ε-Caprolactone
Catalysts 2015, 5(3), 1425-1444; https://doi.org/10.3390/catal5031425
Received: 9 July 2015 / Revised: 27 July 2015 / Accepted: 31 July 2015 / Published: 11 August 2015
Cited by 4 | PDF Full-text (837 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Three sterically-enhanced 2-imino-6-(1-naphthyl)pyridines, 2-{CMe=N(Ar)}-6-(1-C10H7)C5H3N [Ar = 2,6-i-Pr2C6H3 (L1dipp), 2,4,6-i-Pr3C6H2 (L1tripp), 4-Br-2,6-i-Pr2C
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Three sterically-enhanced 2-imino-6-(1-naphthyl)pyridines, 2-{CMe=N(Ar)}-6-(1-C10H7)C5H3N [Ar = 2,6-i-Pr2C6H3 (L1dipp), 2,4,6-i-Pr3C6H2 (L1tripp), 4-Br-2,6-i-Pr2C6H2 (L1Brdipp)], differing only in the electronic properties of the N-aryl group, have been prepared in high yield by the condensation reaction of 2-{CMe=O}-6-(1-C10H7)C5H3N with the corresponding aniline. Treatment of L1dipp, L1tripp and L1Brdipp with two equivalents of AlMe3 at elevated temperature affords the distorted tetrahedral 2-(amido-prop-2-yl)-6-(1-naphthyl)pyridine aluminum dimethyl complexes, [2-{CMe2N(Ar)}-6-(1-C10H7)C5H3N]AlMe2 [Ar = 2,6-i-Pr2C6H3 (1a), 2,4,6-i-Pr3C6H2 (1b), 4-Br-2,6-i-Pr2C6H2 (1c)], in good yield. The X-ray structures of 1a1c reveal that complexation has resulted in concomitant C–C bond formation via methyl migration from aluminum to the corresponding imino carbon in L1aryl; in solution, the restricted rotation of the pendant naphthyl group in 1 confers inequivalent methyl ligand environments. The ring opening polymerization of ε-caprolactone employing 1, in the presence of benzyl alcohol, proceeded efficiently at 30 °C producing polymers of narrow molecular weight distribution with the catalytic activities dependent on the nature of the substituent located at the 4-position of the N-aryl group with the most electron donating i-Pr derivative exhibiting the highest activity (1b > 1a > 1c); at 50 °C 1b mediates 100% conversion of the monomer to polycaprolactone (poly(CL)) in one hour. In addition to 1a, 1b and 1c, the single crystal X-ray structures are reported for L1dipp and L1tripp. Full article
(This article belongs to the Special Issue Molecular Catalysis for Precise Olefin Polymerization and ROP 2015)
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Open AccessCommunication Photohydrogenation of Acetophenone Using Coumarin Dye-Sensitized Titanium Dioxide under Visible Light Irradiation
Catalysts 2015, 5(3), 1417-1424; https://doi.org/10.3390/catal5031417
Received: 13 June 2015 / Revised: 27 July 2015 / Accepted: 28 July 2015 / Published: 4 August 2015
Cited by 3 | PDF Full-text (1140 KB) | HTML Full-text | XML Full-text
Abstract
The use of coumarin dyes adsorbed on titanium dioxide (TiO2, P25) successfully extended the photocatalytic UV response of TiO2 toward visible light region. The hydrogenation of acetophenone (AP) using TiO2 modified with coumarin dyes proceeded with good chemical efficiencies
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The use of coumarin dyes adsorbed on titanium dioxide (TiO2, P25) successfully extended the photocatalytic UV response of TiO2 toward visible light region. The hydrogenation of acetophenone (AP) using TiO2 modified with coumarin dyes proceeded with good chemical efficiencies under visible light irradiation. The role of sacrificial reagents on this dye-sensitized system is also reported. Full article
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Open AccessArticle The Use of C-MnO2 as Hybrid Precursor Support for a Pt/C-MnxO1+x Catalyst with Enhanced Activity for the Methanol Oxidation Reaction (MOR)
Catalysts 2015, 5(3), 1399-1416; https://doi.org/10.3390/catal5031399
Received: 23 May 2015 / Revised: 17 July 2015 / Accepted: 22 July 2015 / Published: 30 July 2015
Cited by 7 | PDF Full-text (1318 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Platinum (Pt) nanoparticles are deposited on a hybrid support (C-MnO2) according to a polyol method. The home-made catalyst, resulted as Pt/C-MnxO1+x, is compared with two different commercial platinum based materials (Pt/C and PtRu/C). The synthesized catalyst
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Platinum (Pt) nanoparticles are deposited on a hybrid support (C-MnO2) according to a polyol method. The home-made catalyst, resulted as Pt/C-MnxO1+x, is compared with two different commercial platinum based materials (Pt/C and PtRu/C). The synthesized catalyst is characterized by means of FESEM, XRD, ICP-MS, XPS and μRS analyses. MnO2 is synthesized and deposited over a commercial grade of carbon (Vulcan XC72) by facile reduction of potassium permanganate in acidic solution. Pt nanoparticles are synthesized on the hybrid support by a polyol thermal assisted method (microwave irradiation), followed by an annealing at 600 °C. The obtained catalyst displays a support constituted by a mixture of manganese oxides (Mn2O3 and Mn3O4) with a Pt loading of 19 wt. %. The electro-catalytic activity towards MOR is assessed by RDE in acid conditions (0.5 M H2SO4), evaluating the ability to oxidize methanol in 1 M concentration. The synthesized Pt/C-MnxO1+x catalyst shows good activity as well as good stability compared to the commercial Pt/C based catalyst. Full article
(This article belongs to the Special Issue Electrocatalysis in Fuel Cells) Printed Edition available
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Open AccessArticle Sb Surface Modification of Pd by Mimetic Underpotential Deposition for Formic Acid Oxidation
Catalysts 2015, 5(3), 1388-1398; https://doi.org/10.3390/catal5031388
Received: 13 May 2015 / Revised: 22 July 2015 / Accepted: 22 July 2015 / Published: 28 July 2015
Cited by 2 | PDF Full-text (449 KB) | HTML Full-text | XML Full-text
Abstract
The newly proposed mimetic underpotential deposition (MUPD) technique was extended to modify Pd surfaces with Sb through immersing a Pd film electrode or dispersing Pd/C powder in a Sb(III)-containing solution blended with ascorbic acid (AA). The introduction of AA shifts down the open
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The newly proposed mimetic underpotential deposition (MUPD) technique was extended to modify Pd surfaces with Sb through immersing a Pd film electrode or dispersing Pd/C powder in a Sb(III)-containing solution blended with ascorbic acid (AA). The introduction of AA shifts down the open circuit potential of Pd substrate available to achieve suitable Sb modification. The electrocatalytic activity and long-term stability towards HCOOH electrooxidation of the Sb modified Pd surfaces (film electrode or powder catalyst) by MUPD is superior than that of unmodified Pd and Sb modified Pd surfaces by conventional UPD method. The enhancement of electrocatalytic performance is due to the third body effect and electronic effect, as well as bi-functional mechanism induced by Sb modification which result in increased resistance against CO poisoning. Full article
(This article belongs to the Special Issue Electrocatalysis in Fuel Cells) Printed Edition available
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Open AccessArticle Simple Preparation of Pd Core Nanoparticles for Pd Core/Pt Shell Catalyst and Evaluation of Activity and Durability for Oxygen Reduction Reaction
Catalysts 2015, 5(3), 1375-1387; https://doi.org/10.3390/catal5031375
Received: 18 May 2015 / Revised: 14 July 2015 / Accepted: 18 July 2015 / Published: 28 July 2015
Cited by 6 | PDF Full-text (1689 KB) | HTML Full-text | XML Full-text
Abstract
Pd core nanoparticles less than 5 nm in mean size were prepared on carbon black (CB) without any stabilizer by using palladium acetate as a precursor and CO as a reducing agent, and then used for preparing Pd core/Pt shell nanoparticles-loaded CB (Pt/Pd/CB).
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Pd core nanoparticles less than 5 nm in mean size were prepared on carbon black (CB) without any stabilizer by using palladium acetate as a precursor and CO as a reducing agent, and then used for preparing Pd core/Pt shell nanoparticles-loaded CB (Pt/Pd/CB). The mean size of Pd nanoparticles could be controlled by the concentration of palladium acetate and the CO bubbling time. The cyclic voltammograms of two Pd nanoparticles-loaded CB (Pd4.2/CB, Pd3.3/CB) electrodes whose mean size was 4.2 and 3.3 nm, respectively, had characteristics similar to a Pt electrode after the formation of a Pt monolayer shell, suggesting that the Pd core nanoparticles were almost covered with the Pt monolayer shell. The oxygen reduction reaction (ORR) on both Pt/Pd/CB proceeded in 4-electron reduction mechanism. Both Pt/Pd/CB electrodes was ca. 1.5 times higher in ORR activity per electrochemical surface area of Pt (specific activity, SA) than the commercial Pt nanoparticles-loaded CB (Tanaka Kikinzoku Kogyo, Pt/CB-TKK) electrode, and the Pt/Pd3.3/CB electrode had higher SA than the Pt/Pd4.2/CB electrode. The ORR activity per unit mass of Pt for both Pt/Pd/CB electrodes was 5.0 and 5.5 times as high as that for the Pt/CB-TKK electrode, respectively. The durability of both Pt/Pd/CB electrodes was comparable to that of Pt/CB-TKK. Full article
(This article belongs to the Special Issue Electrocatalysis in Fuel Cells) Printed Edition available
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