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Multiwalled carbon nanotubes and Vulcan carbon were functionalized with a 30 %v/v hydrogen peroxide solution and employed as supports for Pt and PtSn catalysts prepared by the polyol method. PtSn catalysts with a Pt loading of 20 wt.% and a Pt : Sn atomic ratio equal to 3 : 1 were evaluated in the ethanol electrooxidation reaction. The effects of the oxidizing treatment on the surface area and the surface chemical nature were analyzed through N 2 adsorption, isoelectric point, and temperature-programmed desorption measurements. Results showed that the H 2 O 2 treatment affects the surface area of the carbons to a great extent. Characterization results indicated that the performance of the electrocatalysts strongly depends both on the presence of Sn and on the support functionalization. PtSn/CNT-H 2 O 2 electrocatalyst displays a high electrochemical surface area and enhanced catalytic activity for ethanol oxidation in comparison to other catalysts in the present study., (© 2023 Wiley-VCH GmbH.)

The corrosion stability of a series of carbon supports of various porous structure and morphology: commercial carbon blacks, carbon–carbon composite, and multiwall carbon nanotubes was studied using start-stop protocol cycling (1–1.5 V vs reversible hydrogen electrode (RHE) potential range with 0.5 V/s of scan rate) in an electrochemical cell at 25 °C using 0.1 M HClO 4 as electrolyte. Two stability regions were revealed for the first time depending on the cycle number. The first one is characterized by a constant value of quinone/hydroquinone (QH) transition potential. In the second part anode and cathode QH peaks gradually shift toward higher and lower potentials respectively, which is due most likely to a complete degradation of the supports. We proposed an effective resistance (R eff ) as the corrosion stability parameter that can be easily obtained from the cyclic voltammetry (CV) data. Based on these results, a model of corrosion of porous carbon materials supported on glassy carbon rod was proposed. It was shown that the decrease in the R eff of the samples in the initial stages of degradation is due to the increase in the number of QH groups on the surface, while a sharp increase in the R eff upon further cycling can be explained by a decrease in the number of contacts between the carbon grains. [ABSTRACT FROM AUTHOR]

The propensity of carbon support for methanation in a hydrogen-containing medium is a problem for active ruthenium ammonia synthesis catalysts, since this leads to the degradation of the support and the sintering of the active component. This review analyses some key works on approaches to methanation inhibition and their results to show that, on the whole, an algorithm for solving the methanation problem has been found, i.e., the graphitization of carbon supports at high temperatures (up to 2000°C) and the introduction of ruthenium promoters, specifically alkali (Cs, K) and alkali-earth (Ba) oxides, whose role is to modify the electron state of ruthenium and block the surface of a carbon support to prevent it from interacting with active hydrogen. The most efficient catalyst not liable to methanation up to 700°C and a hydrogen pressure of 100 atm has been found. The resulting analysis can be useful in selecting and preparing Me/C catalysts in which Me represents metals of the VIII Group and others. [ABSTRACT FROM AUTHOR]

Developing new synthetic methods for carbon supported catalysts with improved performance is of fundamental importance in advancing proton exchange membrane fuel cell (PEMFC) technology. Continuous-flow, microfluidic reactions in capillary tube reactors are described, which are capable of synthesizing surfactant-free, ultrafine PtSn alloyed nanoparticles (NPs) on various carbon supports (for example, commercial carbon black particles, carbon nanotubes, and graphene sheets). The PtSn NPs are highly crystalline with sizes smaller than 2 nm, and they are highly dispersed on the carbon supports with high loadings up to 33 wt %. These characteristics make the as-synthesized carbon-supported PtSn NPs more efficient than state of the art commercial Pt/C catalysts applied to the ethanol oxidation reaction (EOR). Significantly enhanced mass catalytic activity (two-times that of Pt/C) and improved stability are obtained. [ABSTRACT FROM AUTHOR]

The applicability of a porous carbon material obtained as a result of the 'chemical' dehydrochlorination of chlorinated polyvinyl chloride as a support for palladium hydrogenation catalysts was demonstrated. The efficiency of the catalyst was evaluated in the liquid-phase reactions of nitrobenzene hydrogenation and chlorobenzene hydrodechlorination. Although the specific activity of the catalyst was lower by a factor of 3-4 than that of the samples based on Sibunit and carbon nanotubes, the complete conversion of the initial compounds with the selective formation of end products under mild conditions was achieved at a relatively low palladium content (1.5%). [ABSTRACT FROM AUTHOR]

Hydrogen interaction with ruthenium surfaces is a complex phenomenon that can play an important role in catalytic reactions such as ammonia synthesis. In this study, H 2 /D 2 isotopic homomolecular exchange has been used to characterize four different catalytic surfaces, namely Ru/AC 0 , Ru/AC 1 , Ru-Na/AC 0 and Ru-Na/AC 1 . They are composed of 2%Ru or 2%Ru-4.5%Na supported on an active carbon with (AC 0 ) and without surface groups (AC 1 ). The AC 1 carbon (1162 m 2 g −1 ) is obtained by treatment of AC 0 (960 m 2 g −1 ) in N 2 at 900 °C. Ru/AC 0 and Ru/AC 1 catalysts are prepared by impregnation of the supports with aqueous solutions of Ru(NO)(NO 3 ) 3 . Na-promoted catalysts are then prepared by impregnation of Ru catalysts with NaOH solutions. An overall picture of the surface mobility phenomena on the four different catalytic surfaces has been described. It has been demonstrated that the presence of Na promoter in Ru-Na/AC 0 and Ru-Na/AC 1 catalysts inhibits the spillover of H atoms from the Ru particles to the AC surface. However, for non Na promoted catalysts, the extension of the H spillover phenomenon depends on the amount of oxygen groups present on the AC surface. Likewise, the formation of a ruthenium hydride during the reduction treatment is suggested for catalysts promoted or not by Na. Finally, this work shows how the kinetics of the H 2 /D 2 isotopic exchange reaction may be related to the surface electron density of the catalyst, which allows us to better understand the effect that both promoter and support have on the metal particles. [ABSTRACT FROM AUTHOR]

This work focuses on the catalytic activity and surface modification of Vulcan XC 72R and Printex L6 toward the oxygen reduction reaction (ORR) after the carbon supports were subjected to a pre-treatment with nitric acid or ammonia. The results indicated that acid-treated Printex L6 was the best-suited material toward the two-electron pathway of the ORR. This material contained the largest concentration of oxygenated acid species and hydrogen, as determined by XPS, the Boehm method, and elemental analysis. The enhanced formation of HO for acid-treated Printex L6 can be explained by the presence of oxygenated acid species increasing the hydrophilic character of the carbon support. The hydrophilicity of the material was investigated by contact angle measurements. However, the changes of the surface area, porosity, and the aliphatic chains of the carbons induced by the pre-treatments and the contributions of these factors to HO production cannot be disregarded. [ABSTRACT FROM AUTHOR]

Samples of barium-promoted carbon-supported cobalt catalysts for ammonia synthesis were prepared; the cobalt content was constant (27.4 wt %) and the amount of barium introduced differed within the range of 0-0.88 mmol gC+Co−1. Turbostratic carbon was used as the support. Several techniques, including X-ray powder diffraction, TEM, Thermogravimetric analysis-mass spectrometry (methanation studies) and H2 temperature-programmed desorption were used to examine the properties of the carbon support or catalytic materials. The reaction rate measurements were performed under the following conditions: T=400 °C, p=9.0 MPa, x [ABSTRACT FROM AUTHOR]

The influence of different surface modifications of carbon supports on the corrosion resistance of 50 wt % Pt/C catalysts on their basis was studied. The corrosion resistance was measured from changes in the electroactive surface area of platinum in the course of potential cycling from 1.0 to 1.5 V versus the reversible hydrogen electrode (potential sweep rate, 0.5 V/s) during 60000 cycles. A 40% Pt/Vulcan XC-72 commercial catalyst was used as the reference sample. The supports were modified by the carbonization of the high surface area carbon black Ketjenblack DJ-600 and by the additional activation of the carbon-carbon composite Sibunit-1562. It was found that the preliminary carbonization of the Ketjenblack DJ-600 support with a propane-butane mixture at 770°C and the activation of Sibunit-1562 with subsequent thermal treatment at 500°C increased and decreased, respectively, the corrosion resistance of the 50 wt % Pt/C catalysts on their basis. [ABSTRACT FROM AUTHOR]

The study considered the formation and catalytic properties of the active sites in Pd/C and Ru/C catalysts supported on carbon nanotubes (CNT) and carbon black (CB). The nature of carbon support was shown to affect the dispersion of supported metal and its catalytic properties in the aqueous-phase hydrogenation of furfural. The 1.5% Pd/CB catalyst demonstrated a high selectivity (99%) for furfuryl alcohol during hydrogenation of furfural at a temperature of 50 °C and hydrogen pressure of 0.5 MPa. The 1.5% Pd/CNT catalyst was not active under mild conditions of the reaction (50 °C, 0.5 MPa), but had a greater tendency to reduce the furan ring under severe conditions (90 °C, 0.5 or 2.0 MPa) as demonstrated by an increased yield of tetrahydrofurfuryl alcohol. The ruthenium samples showed a low activity in aqueous-phase hydrogenation of furfural irrespective of the support nature and reaction conditions, possibly due to irreversible adsorption of water on the active sites. [ABSTRACT FROM AUTHOR]

The electrochemical oxygen reduction reaction (ORR) on bare (100)Pt nanoparticles supported by molybdenum-carbide-derived carbon [(100)Pt-C(Mo2C)] with high specific surface area and controlled microporosity-mesoporosity, pore size distribution, electrical conductivity, and corrosion stability was studied in 0.5 M H2SO4 solution by using rotating-disk-electrode and cyclic voltammetry methods. The C(Mo2C) powder was prepared from Mo2C at a fixed chlorination temperature (750 °C). Pt nanoparticles were prepared through colloid chemistry and deposited onto/into C(Mo2C) and Vulcan XC72 carbon supports for comparison. The ORR cathodic current densities and half-wave potentials strongly depend on the characteristics of the carbon material used as the support. High values for the ORR current density were calculated for (100)Pt-C(Mo2C) and the half-wave potential is nearly 80 mV more positive compared with that for the (100)Pt-Vulcan XC72 catalyst with a similar catalyst loading. [ABSTRACT FROM AUTHOR]

A simple method for preparation of Pd catalysts supported on low-surface-area inorganic powders as carbons, oxides (SiO 2 , diatomites, WO 3 , Ta 2 O 5 , Nb 2 O 5 , V 2 O 5 , TiO 2 , CeO 2 , ZrO 2 , Ga 2 O 3 , In 2 O 3 , Cr 2 O 3 , Fe 2 O 3 , Al 2 O 3 ) and salts (CaF 2 , BaSO 4 , Ca 3 (PO 4 ) 2 ) was developed. It implies hydrolytic deposition of Pd(II) precursors onto a support in basic solutions. Regularities of the hydrolysis process without and in the presence of the support are studied by various physicochemical methods. A scheme of the formation of catalytically active component was put forward. Reduced with H 2 at 50–120 °C, the palladium catalysts demonstrate strong dependence of their specific activity in hydrogenation of aqueous maleic acid on the support nature. TOF value for palladium nanoparticles supported onto an oxide surface slows down with increasing polarizing ability of cations in the lattice of the oxide, that testifies to the influence of the electrostatic field intensity at the support surface on the reaction rate. [ABSTRACT FROM AUTHOR]

This study deals with the production and activation of biochars and their use as supports for a series of ruthenium catalysts for hydrogenation of l -arabinose/ d -galactose sugar mixture. The synthesized biochars differ in physicochemical properties and surface chemistry influencing ruthenium metal uptake and dispersion and as a consequence its catalytic behaviour. Selectivity exceeding 95% was observed for both hexitols. The catalytic performance of the prepared Ru supported catalysts is also compared to the already known Ru/activated carbon commercial catalyst. [Display omitted] • Ruthenium-biochar micro and mesoporous catalysts. • l -Arabinose undergoing much faster hydrogenation than d -Galactose. • Increase in textural properties of the supports led to an increase in catalytic activity. • Catalytic activity of all ruthenium containing samples is size dependent. [ABSTRACT FROM AUTHOR]

An efficient method was proposed for preparing supported platinum nanoparticles on the graphite by the deposition of Pt(0) binuclear clusters. The one-step method serves to promptly deposite Pt particles with a uniform morphology avoiding the use of additional reagents, such as reducing agents and stabilizers, which can be sorbed by carbon supports to contaminate the catalysts. Electron microscopy revealed an average size of platinum nanoparticles of 3-4 nm and a narrow particle-size distribution. [ABSTRACT FROM AUTHOR]

Direct methanol fuel cells (DMFCs) have been the focus of future research because of their simple structure, abundant fuel sources, high energy conversion efficiency and low cost. Among the components in DMFC, the activity and stability of the cathode catalyst is the key to the performance and lifetime of the DMFCs. Oxygen reduction reaction (ORR) is an important electrode reaction on DMFC cathode. It is known that Pt is widely used in the fabrication of ORR catalysts, but the limited earth storage of Pt and its high price limit the use of Pt-based commercial catalysts in DMFCs. To overcome these problems, advances have been made on new low Pt-based catalysts and Pt-free catalysts in recent years. In this article, the development of novel ORR catalysts and the carbon supports is reviewed and discussed., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Qin, Tian, Wang, Jiang and Jiang.)

Elevated by the support: 2‐Alkynyl aniline cycloisomerization to indole is catalyzed by cationic Au NPs on a carbon support. Electroneutral and rich 2‐aryl indoles are further converted into 3,3′‐biindoles by oxidative homocoupling that is readily catalyzed by the Au NPs on carbon, and exclusively but also somewhat sluggishly by the carbon support. [ABSTRACT FROM AUTHOR]

Abstract: Chemisorption of CO combined with microcalorimetry has been applied to study the nature, number and adsorption strength distribution of surface sites exposed by carbon-supported Ru catalysts. A comparative analysis of the CO chemisorption on different Ru catalysts, prepared using two different metal precursors, RuCl3·xH2O and Ru(NO)(NO3)3, has been carried out. An activated carbon and the corresponding derivative where oxygen surface groups were incorporated, as well as carbon nanotubes and a high surface area graphite, were used as catalytic supports. Based on previous temperature programmed reduction studies, all the catalysts were reduced under hydrogen flow at 523K or at 573K. The CO adsorption differential enthalpy profiles show that Ru(NO)(NO3)3 precursor produces more homogeneous surface site distribution in the Ru nanocrystals, in comparison with those prepared from RuCl3, as well as higher values of enthalpies in the medium range of coverage. As a possible explanation for this effect, residual chloride species remaining after reduction treatment in the ex-chloride catalysts, that can be anchored to the Ru nanoparticles weakening the CO adsorption, have been considered. This behavior occurs for the three studied carbon supports. On the other hand, the oxygen surface groups incorporated on the activated carbon seem not to modify the CO adsorption properties of the catalysts, independently of the precursor employed. [Copyright &y& Elsevier]

Highlights: [•] Successful synthesis of boron-doped B-HCSs and B-CNTs by using a CVD method. [•] Pd was well dispersed on Pd/B-HCS and Pd/B-CNT catalysts (2–8nm) with size determined by calcination temperature. [•] Pd/B-HCS and Pd/B-CNT catalysts are selective, highly efficient, and reusable catalyst for the solvent-free oxidation of benzyl alcohol. [•] Activity was controlled by Pd size as determined by calcination temperature of catalysts. [ABSTRACT FROM AUTHOR]

Characteristic features of Pt/C catalysts prepared through reductive deposition from an aqueous solution have been investigated. The carbon support was found to act as an effective nucleating agent and to ensure the formation of small and predominantly nonaggregated Pt particles, probably through a preliminary formation of oxide nuclei on the carbon surface. The deposition rates could be high enough to provide the location of Pt nanoparticles near the external surface of the support and outside micropores. The depositions onto bare carbon supports and Pt/C samples presynthesized by using another method proved equally effective, which thus opened a route to various types of metal distribution. With the same metal precursor, reductant, and base (H2PtCl6, NaOOCH, Na2CO3), catalytic properties could be influenced through the support, Pt loading, and deposition conditions. In the oxidation of isopropyl alcohol as a model test reaction, alcohol conversion could be as high as 99.7 % and turnover frequencies 80 000 h−1 [H2O, O2, 1 bar (100 kPa), 30 °C]. [ABSTRACT FROM AUTHOR]

Abstract: Gold-carbon hybrids have been efficiently used as catalysts for the hydroamination of phenylacetylene with aniline. Carbon supports (single-walled and multi-walled carbon nanotubes, graphene oxide, graphite, graphitic cones, nanodiamond, ordered mesoporous carbon, carbon xerogel, carbon black, activated carbon, and laser-ablation produced carbon foam) were homogenously decorated with gold nanoparticles (GNP) synthesized by in situ reduction of chloroauric acid (H[AuCl4]) in water. The performance of carbon materials used as catalytic supports has been here evaluated. The synthesized gold-carbon hybrids worked remarkably well as catalysts for the targeted reaction. Conversion values as high as 79% were achieved by suitably adjusting the gold:carbon support w/w ratios. Our results indicate that the catalytic activity strongly depends on gold:carbon support w/w ratios and on the structure and textural properties and dispersibility of the carbon supports used. Thus, the best gold-carbon catalyst performance in terms of conversion values and low carbon support content has been achieved when using graphene oxide as well as supports (carbon black, carbon nanotubes, and nanodiamond) that combine high BET surface areas, well-developed mesoporosity, and good dispersibility in water during the GNP decoration process. [Copyright &y& Elsevier]

In the series of studied Pd/C catalysts, the highest selectivity for benzyl alcohol formation with complete conversion of benzaldehyde was demonstrated by the sample containing 1% palladium supported on carbon nanotubes when the reaction was carried out at 40 °C and 0.5 MPa. The 0.3% Pd/C catalysts have low activity. Increasing the palladium content and raising the reaction temperature leads to an increase in the toluene fraction in the reaction products. [ABSTRACT FROM AUTHOR]

Abstract: The deposition of Pt oxide from aqueous chloroplatinate solutions onto carbon supports (activated carbons, carbon blacks, carbon nanofibers) with the aid of Na2CO3 and without adding the reductants or wetting agents was studied. It has been revealed that carbons accelerate greatly the hydrolysis of chloroplatinate, and the hydrolytic deposition can therefore interfere with the other preparation methods. Neutral pH was found optimum for heterogeneous nucleation and formation of smaller PtO x particles. High temperature (80°C) allowed depositions of 5–30wt.% of Pt for a short time (1–3h) but did not affect Pt dispersions (15–90% at surface concentration of Pt 0.5–30μmol/m2). The supported particles could be further reduced in the liquid phase with minimal losses of the dispersion (Na-formate as reductant). The heterogeneous nucleation ensured a uniform distribution of Pt particles but provoked particle confinement in narrow pores. The possibility of influencing catalytic properties with the aid of the support, Pt loading and deposition conditions was demonstrated (hydrogenation of cycloalkenes as a model structure-insensitive reaction and oxidation of isopropyl alcohol as structure-sensitive one). [Copyright &y& Elsevier]

Abstract: The intention of the study presented here is to compare the electrochemical oxidation tendencies of a pristine Ketjen Black EC300 high surface area (HSA) carbon black, and four graphitised counterparts heat-treated between 2100 and 3200 °C, such as those typically used as corrosion resistant carbon (CRC) supports for polymer electrolyte membrane fuel cell (PEMFC) catalysts. A methodology combining cyclic voltammetry (CV) and differential electrochemical mass spectrometry (DEMS) is used, which allows the characterisation and comparison of the complete electrochemical oxidation rates and behaviours of the various carbon blacks. It is observed that the behaviour of the carbon black towards electrochemical oxidation is highly dynamic, and dependent on the properties of the pristine carbon back, the degree of electrochemical oxidation and the potential pre-history. The behaviour of the non-graphitised and CRC samples graphitised ≤2450 °C suggests that electrochemical oxidation leads to the passivation of the carbon, which when reduced in a potential excursion to ≤0.24 VRHE is lost allowing subsequent oxidation; however, CRC samples graphitised ≥2800 °C did not exhibit this same behaviour. [Copyright &y& Elsevier]

Abstract: The promoting effect of incorporation of carbon atoms into the crystalline lattice of palladium on its electrocatalytic performance for the hydrogen oxidation reaction (HOR) and CO tolerance was found, for the first time, with the PdC x /C catalysts prepared via (1) treatment of the pre-deposited Pd particles with C2H4 at 300°C and (2) successive calcination/reduction of a Pd/C precursor in flowing Ar and H2 at 250°C. The formation of the interstitial PdC x solutions was confirmed by means of X-ray diffraction, high resolution transition electron microscopy and a set of electrochemical methods. The HOR on the as-prepared and CO-poisoned PdC x /C catalysts was studied using rotating disk electrode. For the catalysts prepared without the use of specially added carbon source (route 2), the correlation between the microstructure of a carbon support and the catalyst activity for the HOR is observed: the structurally more disordered supports give rise to the more active catalysts. The most active PdC x /C catalysts demonstrate up to a 2.5-fold increase in the exchange current density of the HOR and a rise of about 20-fold in the hydrogen oxidation current density in the presence of 1100ppm CO comparing to the Pd/C catalysts. [Copyright &y& Elsevier]

Abstract: As an alternative to oxidative acid treatment, a hydrophobic graphitized carbon nanotube (CNT) was functionalized with 1–4 nm thick polypyrrole (PPy) prior to application as catalyst supports in polymer electrolyte membrane (PEM) fuel cells. Unlike oxidative acid treatment, the PPy coating method converts the hydrophobic surface of a CNT to a hydrophilic one without creating defects on the surface of the CNT. As a result, Pt nanoparticles deposited on the PPy-coated CNTs showed an improved distribution, which significantly enhanced the fuel cell performance while preserving the intrinsic properties of the CNTs, i.e., resistance to electrochemical carbon corrosion. An additional advantage of PPy coating is that it prevents Pt nanoparticles from agglomerating on the CNT surface. These results indicated that PPy-coated CNTs are a promising catalyst support to improve both the performance and durability of PEM fuel cells. [Copyright &y& Elsevier]

New catalysts for the ammonia synthesis from dinitrogen and dihydrogen based on supported mononuclear potassium carbonyl ruthenate KRu[(CO)] as a precursor of catalytically active particles have been developed. Magnesium oxide and graphite-like active carbon Sibunit were used as supports, while aliphatic organolithium compounds (BuLi and BuLi) were employed as electron promoters in these catalysts. The systems with MgO as a support are the most efficient. The introduction of RLi into these systems allows one to considerably increase the ammonia synthesis rate. When using carbon Sibunit, the promoting effect of organolithium compounds is much weaker but the activity of such catalysts can be essentially increased by the introduction of an additional electron promoter, viz., metallic potassium, into the system. All the catalysts tested are active in the ammonia synthesis at atmospheric pressure and temperatures ≥250 °C. [ABSTRACT FROM AUTHOR]

Abstract: A series of carbon supported bimetallic Pt―Cu catalysts were prepared and used for glycerol oxidation with oxygen in a base-free aqueous solution. It was found that bimetallic Pt―Cu/C was more active than monometallic Pt/C towards selective oxidation of glycerol to glyceric acid. The selectivity of free glyceric acid reached 70.8% at an 86.2% conversion of glycerol over 5Pt―Cu/C. Highly dispersed bimetallic Pt―Cu nanoparticles with small particle size in dominant alloyed phase of PtCu3 were confirmed by XRD and TEM in the bimetallic Pt―Cu/C catalyst, which is proposed to contribute to the improved performance. [Copyright &y& Elsevier]

Pt/carbon black samples fabricated from dimethyl (1,5-cyclooctadiene) platinum(II) in supercritical CO are characterized in relation to possible applications in methanol fuel cell. The problem of precise material characterization is addressed in frames of X-ray diffractometry, transmission electron microscopy, and electrochemical techniques of the true surface area determination. The catalysts with Pt loading of 20-40 wt.% consist of nm-size particles, with the lattice defectiveness dependent on the fabrication mode. To check the effect of support, various types of carbon blacks (Vulcan XC72R and acetylene black AC-1) are used. In contrast to commercial HiSpec catalysts, no pronounced increase of particle size with Pt loading is found. Specific steady-state activity towards methanol oxidation appears to be essentially higher than for commercial catalysts, mostly because the self-poisoning effects are less pronounced. As for poisoning of Pt with organic species (resulting from the ligand of precursor), its effects are demonstrated to be minor after CO or methanol adsorption accompanied by desorption of contaminating by-product. [ABSTRACT FROM AUTHOR]

Abstract: Carbon-supported MnOOH catalyst was prepared by reducing KMnO4 with carbon Black Pearls 2000. TEM and XRD characterization results show that nanosized tetragonal MnOOH crystals formed in the specimen when the MnOOH content ranged from 9wt.% to 36wt.%. The oxygen reduction reaction (ORR) activity of the catalyst with different amounts of MnOOH content in alkaline media was investigated using a rotating disc electrode (RDE) and a rotating ring-disc electrode (RRDE). The number of electrons involved in the ORR increased from 3.2 to 3.9 with the increase of the MnOOH content from 9wt.% to 36wt.% in the catalyst. The kinetic current increased to 0.0184Acm−2 when the MnOOH content was increased to 72wt.%. However, both the number of electrons and the kinetic current decreased when the MnOOH content was increased from 72wt.% to 90wt.%. The MnOOH/C catalyst with optimized MnOOH content and suitable loading in the cathode is promising for applications in alkaline fuel cells. [Copyright &y& Elsevier]

Abstract: Effect of chemical oxidation of carbon nanofibers (CNFs) on the electrochemical carbon corrosion in polymer electrolyte membrane (PEM) fuel cells is examined. With increasing time of chemical oxidation treatment using an acidic solution, more oxygen functional groups are formed on the surface of CNF resulting in an increasingly hydrophilic carbon surface. This effect contributes to improvements in Pt loading and the distribution of Pt particles on carbon supports. However, the chemical oxidation treatment is found to accelerate electrochemical carbon corrosion. The oxygen functional group and the hydrophilic nature of CNFs after chemical oxidation treatment are believed to encourage the formation of CO2, which is a product of carbon corrosion. From the observed results, it can be concluded that the chemical oxidation of CNFs is beneficial for catalyst loading and distribution. On the other hand, however, it reduces the durability of the PEM fuel cells caused by the electrochemical carbon corrosion. [Copyright &y& Elsevier]

Abstract: Carbon materials such as activated carbon and carbon black have long been used as adsorbents, electrodes, and supports for metal catalysts. However, no attempt has yet been reported to deposit Au as small nanoparticles (NPs) on these carbon materials directly from Au precursor compounds. Until now, the most effective way to support Au NPs on activated carbon was to physically mix a carbon support with Au colloids prepared beforehand. Here we report that Au could be deposited as NPs on carbon materials directly from gold precursor compounds by deposition reduction method and by solid grinding method. In particular, the solid grinding of carbons with dimethyl Au(III) acetylacetonate, which has a certain degree of vapor pressure at room temperature, is a simple technique but surprisingly effective to deposit Au NPs with a mean diameter as small as 1.9nm. These highly dispersed Au NPs on carbon supports were tested for glucose oxidation in water with molecular oxygen. A Au/nanoporous carbon (NPC) catalyst which exhibited relatively high catalytic activity has been kinetically studied for comparison with Au/metal oxides catalysts. [Copyright &y& Elsevier]

Abstract: The catalytic behaviour of Pt supported on carbon-based monoliths was studied in the low-temperature catalytic combustion of benzene, toluene and m-xylene and compared with the corresponding behaviour of Pt supported on γ-Al2O3 coated monoliths. Carbon-based monoliths showed a much better catalytic performance which is ascribed to the fact that the carbon surface is more hydrophobic than the γ-Al2O3 one, and the release of water molecules produced during the combustion is favoured. [Copyright &y& Elsevier]

The effect of fluorination on carbon blacks (CBs) was investigated by analyzing the CB surface functional groups. Also, fluorinated CB supported platinum–ruthenium electrocatalysts were studied. The surface characteristics of the fluorinated CB-supported catalysts were determined by Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS), and their crystallinity was evaluated using X-ray diffraction (XRD). The electrochemical properties of the fluorinated CB-supported platinum and ruthenium (Pt/Ru CBs) catalysts were analyzed by cyclic voltammetry (CV). From the FT-IR results, the introduction of a fluorine atom onto CBs was confirmed by the existence of a carbon–fluorine (C–F) characteristic peak. The XPS result also showed that the fluorine content increased with increasing heat treatment temperature. The XRD analysis revealed that the catalysts are composed of mostly Pt and Ru. This result agreed with the fact that the electrochemical activity of the Pt/Ru CB catalysts was enhanced due to the small size and a high loading of catalysts by surface modification of the CBs. [ABSTRACT FROM AUTHOR]

Abstract: Catalytic wet air oxidation (CWAO) reactions of aniline and phenol were conducted over supported ruthenium catalysts. Three support materials were employed: ZrO2 and graphite, which exhibit medium adsorption capacities for pollutants and present mesopores in their texture, and an activated carbon. This latter has higher adsorption capacity for pollutants because of the large capability of the micropores for contaminant retention from water. The Ru catalysts supported on the activated carbon material showed the higher values of conversion in the oxidation of aniline and of conversion and mineralization in the reaction of phenol. Under our experimental conditions the role of micropores present on the support material seems to be relevant for improving catalytic performances. The incorporation of Ru nanoparticles from different precursors has been also evaluated. Even if the final Ru particle size is a key parameter for the catalytic mineralization, a cooperative effect with the activated carbon support has been established. [Copyright &y& Elsevier]

Abstract: The electrochemical corrosion of carbon catalyst supports in polymer electrolyte membrane (PEM) fuel cells is investigated by monitoring the generation of CO2 using an on-line mass spectrometer at a constant potential of 1.4V. Our results suggest that carbon supports with a high degree of graphitization are more corrosion-resistant, which results in a dramatic improvement of the catalyst durability. We also show that CO2 measurements performed using on-line mass spectrometry represent a time-effective and reliable method for studying the electrochemical corrosion of carbon supports in PEM fuel cells. [Copyright &y& Elsevier]

Abstract: This paper reviews over 100 articles related to heat-treated Fe– and Co–N/C catalysts for the oxygen reduction reaction. The literature shows that through several decades’ effort in the development of non-noble catalysts such as heat-treated Fe– and Co–N/C catalysts, tremendous progress has been made in catalyst synthesis methodologies and the understanding of the mechanism. A heat-treatment step has been identified as necessary for catalyst activity and stability improvement. The enhanced performance of the catalysts is strongly dependent on the carbon support, the source of metal and nitrogen, and the thermal treatment conditions. The metal content in these catalysts also plays an important role in their activity and stability. A saturated metal content has been identified as a major limiting factor for further improvement of catalyst activity. The nitrogen content and the presence of a disordered or heterogeneous phase on the carbon-support surface seem to be the main requirements for an effective catalyst. The mechanisms by which activity and stability are enhanced after the heat treatment of these Fe– and Co–N/C catalysts are not fully understood yet. It is necessary to answer the question of whether or not the metal is part of the active catalytic site, as well as to identify the nature of the catalytic site. A more fundamental understanding will be of great help in designing alternative and innovative routes for catalyst synthesis. In general, the catalytic activity and stability of Fe– and Co–N/C catalysts are still below those of a Pt-based catalyst. However, under the strong driving force of fuel cell commercialization, Pt-free cathode catalysts with methanol tolerance, such as Fe– and Co–N/C, are attractive candidates for solving the problem of the cost of fuel cell catalysts. [Copyright &y& Elsevier]

Abstract: Glucoamylase (GA) was immobilized by adsorption on carbon support: on Sibunit, on bulk catalytic filamentous carbon (bulk CFC) and on activated carbon (AC). This was used to prepare heterogeneous biocatalysts for the hydrolysis of starch dextrin. The effect of the texture characteristics and chemical properties of the support surface on the enhancement of the thermal stability of the immobilized enzyme was studied, and the rates of the biocatalyst’s thermal inactivation at 65–80°C were determined. The thermal stability of glucoamylase immobilized on different carbon supports was found to increase by 2–3 orders of magnitude in comparison with the soluble enzyme, and decrease in the following order: GA on Sibunit>GA on bulk CFC>GA on AC. The presence of the substrate (dextrin) was found to have a significant stabilizing effect. The thermal stability of the immobilized enzyme was found to increase linearly when the concentration of dextrin was increased from 10wt/vol % to 50wt/vol %. The total stabilization effect for glucoamylase immobilized on Sibunit in concentrated dextrin solutions was about 105 in comparison with the enzyme in a buffer solution. The developed biocatalyst, ‘Glucoamylase on Sibunit’ was found to have high operational stability during the continuous hydrolysis of 30–35wt/vol % dextrin at 60°C, its inactivation half-time (t 1/2) exceeding 350h. To improve the starch saccharification productivity, an immersed vortex reactor (IVR) was designed and tested in the heterogeneous process with the biocatalyst ‘Glucoamylase on Sibunit’. The dextrin hydrolysis rate, as well as the process productivity in the vortex reactor, was found to increase by a factor of 1.2–1.5 in comparison with the packed-bed reactor. [Copyright &y& Elsevier]

Abstract: Preparation of hybrid catalysts by immobilization of the complex , abbreviated as Rh(NN)Si, on a wide variety of carbon materials has been investigated. The selected carbon materials, activated carbon, activated carbon fibres, activated carbon cloth, carbon nanotubes and carbon nanofibres, show very different textural properties ranging from narrow micropores to a variety of mesopore sizes. The procedure for anchorage is based on the creation of a covalent bond between the trimethoxysilane functionality in the metal complex and phenol type groups created on the surface of the carbon materials. The supports were characterized by N2 adsorption at 77K, temperature programmed desorption (TPD) and transmission electron microscopy (TEM). The hybrid catalysts were characterized by X-ray photoelectron spectroscopy (XPS), X-ray absorption fine structure (XAFS), and inductively coupled plasma spectroscopy (ICP) for the determination of the metal content. The catalytic activity of the hybrid catalysts was tested in the hydrogenation of cyclohexene and carvone and it was found that they are more active than the homogeneous complex and reusable for at least five consecutive catalytic runs (with no leaching). Among the hybrid catalysts, those prepared with carbon nanotubes and nanofibres are noticeably more active. This behaviour has been attributed to a confinement effect due to the location of the metal complex in the hollow cavity of these supports. [Copyright &y& Elsevier]

Electrodeposition of Pt nanoparticles under potentiostatic conditions was performed on several types of carbon electrode supports: commercial macroporous carbon (a three-dimensional electrode), glassy carbon and graphite. Conducting polymers (poly-aniline and poly- o-aminophenol) were also used. The platinum nanoparticles were obtained by different Potential Step Deposition (PSD) methods in 5 mM H2PtCl6 + 0.5 M H2SO4 aqueous solutions. The effect of the final potential, time and number of steps on the quantity, distribution and size of the platinum nanoparticles was analysed. The mechanism of the electrochemical deposition of platinum was studied through the application of theoretical modelling. The progressive nucleation mechanism provided the closest agreement with the results obtained. In addition, the chemical state and morphology of the electrodeposited materials were determined by means of SEM, TEM and XPS. The results show that the carbon material structure has a strong influence on the Pt particle structure and this, in turn, affects the catalytic activity. [ABSTRACT FROM AUTHOR]

Abstract: Preparation of nanosized palladium (Pd) catalysts supported on various carbon supports using a simple liquid-phase reduction of aqueous Pd complexes with potassium borohydride (KBH4) was investigated. We found that addition of appropriate amounts of sodium hydroxide (NaOH) into aqueous solutions of sodium tetrachloropalladate (Na2PdCl4) followed by reduction with KBH4 produced highly dispersed Pd nanoparticles less than 5nm in diameter on any carbon supports. Ultraviolet–visible light (UV–vis) absorption spectra of aqueous Na2PdCl4 solutions in the presence of various amounts of NaOH clarified the occurrence of partial or complete ligand exchange of the Pd complex from chloride ions (Cl−) to hydroxide ions (OH−). Hence, the production of small Pd nanoparticles on carbon supports is likely to be induced by structural change in the precursor complex prior to the reduction with KBH4. Moreover, evaluation of catalytic activities for liquid-phase oxidation of benzyl alcohol into benzaldehyde using oxygen and hydrogenation of the C cinnamaldehyde with hydrogen revealed that catalytic functions were significantly dependent on the size and the dispersion of Pd particles; i.e., both reactions proceeded efficiently on small Pd catalysts highly dispersed on carbon supports but did not occur efficiently on Pd particles of relatively large sizes or with poor dispersion on those supports. [Copyright &y& Elsevier]