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Luigi Toniolo

Other affiliations: Brown University, National Chemical Laboratory, Hyosung  ...read more
Bio: Luigi Toniolo is an academic researcher from Ca' Foscari University of Venice. The author has contributed to research in topics: Catalysis & Palladium. The author has an hindex of 28, co-authored 144 publications receiving 2598 citations. Previous affiliations of Luigi Toniolo include Brown University & National Chemical Laboratory.


Papers
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Journal ArticleDOI
12 Aug 2014
TL;DR: In this paper, the performance of a core-shell electrocatalyst for proton exchange membrane fuel cells (PEMFCs) was investigated using high-resolution transmission electron microscopy (HR-TEM).
Abstract: The development of affordable energy-conversion systems characterized by a high efficiency and a low environmental impact is one of the most important challenges faced by both fundamental and applied science. Many solutions have been proposed, ranging from advanced secondary batteries based on alkalineand alkaline-earth elements, to supercapacitors and redox flow batteries. One additional family of energy conversion systems that complies with the above requirements includes the various types of fuel cells (FCs), which are open devices that are able to convert the chemical energy obtained from the oxidation of a fuel (usually hydrogen or small organic molecules such as methanol, formic acid or methane) directly into electrical energy. In particular, proton-exchange membrane fuel cells (PEMFCs) arouse significant interest because of their high conversion efficiency and power density; such systems are suitable for a variety of applications ranging from portable electronics to lightduty vehicles. The operation of PEMFCs is bottlenecked by the sluggishness of the oxygen reduction reaction (ORR) in the highly acid environment generated by the electrolyte. Suitable electrocatalysts must be mounted in the device to achieve a performance level compatible with applications. Thus, the development of efficient and affordable ORR electrocatalysts is one of the most critical goals of the research in the field of PEMFCs. 8] Today’s state of the art in ORR electrocatalysts for application in PEMFCs consists of nanocomposite materials including Pt nanocrystals supported on conductive carbon nanoparticles. These electrocatalysts yield an acceptable performance but require a significant loading of platinum, whose abundance in Earth’s crust is very limited and is expected to raise significant risks of supply bottlenecks. 10] Furthermore, Ptbased electrocatalysts show a relatively poor tolerance to common contaminants such as halides and methanol. 12] This report describes the electrochemical behavior of a family of “core-shell” electrocatalysts consisting of a carbon nitride (CN) “shell” matrix and a “core” of conducting carbon nanoparticles (NPs). The CN “shell” matrix embeds PdCoNi alloy NPs and covers homogeneously the carbon “core”. The chemical composition of the materials is determined by inductively-coupled plasma atomic emission spectroscopy (ICP-AES) and microanalysis ; the structure is studied by powder X-ray diffraction (powder XRD); the morphology is investigated by high-resolution transmission electron microscopy (HR-TEM). The surface activity and structure are probed by CO stripping. The oxygen reduction reaction (ORR) kinetics, reaction mechanism, and tolerance towards contamination from chloride anions are evaluated by cyclic voltammetry with the thin-film rotating ring-disk electrode (CV-TF-RRDE) method. The effect of N concentration in the matrix (which forms “coordination nests” for the Pdbased alloy NPs bearing the active sites) on the ORR performance of the electrocatalysts is described. Results show that N atoms: 1) influence the evolution of the structure of the materials during the preparation processes, and 2) interact with alloy NPs, affecting the bifunctional and electronic ORR mechanisms of active sites and the adsorption/desorption processes of oxygen molecules and contaminants. Finally, the best PdCoNi electrocatalyst shows a higher surface activity in the ORR at 0.9 V vs. RHE with respect to the Pt-based reference (388 mA cmPd -2 vs. 153 mA cmPt ).

94 citations

Journal ArticleDOI
TL;DR: In this article, the acyl complex PdCl(COR)(PPh3)2 (R = Et, n-Hex), isolated during the course of hydro-carbalkoxylation reactions catalyzed by the precursor system PdCL2(PPh 3)2-PPh4 (95°C, P(CO) 100-120 atm; Pd: P = 1:3-4), in ethanol or higher alkanols as solvents, reacts with an alkanol R'OH in the presence of added P

82 citations

Journal ArticleDOI
TL;DR: In this paper, the mechanism of hydroesterification of styrene using in situ-formed Pd(OTs) 2 (PPh 3 ) 2 from PdOAc) 2, PPh 3 and TsOH in methanol has been investigated by isolation and characterisation of catalytically active intermediates.

75 citations

Journal ArticleDOI
TL;DR: In this article, a new class of "core-shell" electrocatalysts for oxygen reduction reaction (ORR) processes for application in Proton Exchange Membrane Fuel Cells (PEMFCs) is described.

73 citations

Journal ArticleDOI
TL;DR: In the case of copolymerization, it was shown in this article that the catalytic cycle is initiated by the insertion of carbon monoxide with water on the metal center, via a reaction closely related to the water gas shift reaction.
Abstract: For the title copolymerization the catalyst productivity (g-polymer/g-Pd · h) is significantly influenced by the presence of water and of the acid as it passes through a maximum upon increasing concentration of H2O and of TsOH. In the presence of 450 ppm of H2O, the maximum productivity is ca. 3.7 times higher than when the copolymerization is carried out in the presence of 1% of trimethylorthoformate, used as H2O scavenger in MeOH as solvent, at 90°C, under 45 atm of total pressure, employing the catalyst precursor in the molar ratio Pd/dppp/TsOH 1/1/2 ([Pd] 5.6 × 10−5 mol · 1−1). Under similar conditions, but under 60 atm of the two monomers, in the presence of 900 ppm of H2O and when employing an excess of the acid ( TsOH Pd 6.4) the productivity reaches a maximum of ca. 11500 g-polymer/g-Pd · h, which is 1.4 times higher than that obtained when the TsOH Pd ratio is 2 1 . The promoting effect of H2O is ascribed to the possibility that a higher concentration of active PdH species, which are proposed to initiate the catalytic process through the insertion of the olefin into a PdH bond, is achieved through the interaction of carbon monoxide with water on the metal center, via a reaction closely related to the water gas shift reaction. It is also proposed that the promoting effect of the acid is due to the reactivation of inactive Pd(0) species, which inevitably form under the reducing reaction conditions, with formation of active PdH species. When the copolymerization is carried out in the presence of benzoquinone (BQ), either under the reaction conditions in which the productivity reaches a maximum or under unfavorable conditions, that is, in the presence of low or relatively high concentrations of water, the productivity has an average value of ca. 7000 g-polymer/g-Pd · h. Since it was found by other research groups that in the presence of BQ the polymer takes origin mainly through the insertion of CO into a PdOCH3 species whose formation is favored in the presence of BQ, the findings presented above give further support to the suggestion that the promoting effect of H2O and of TsOH are due to the possibility that, when present in appropriate amounts, they favour the formation of PdH species which start the catalytic cycle.

68 citations


Cited by
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Journal ArticleDOI
TL;DR: This comprehensive Review focuses on the low- and non-platinum electrocatalysts including advanced platinum alloys, core-shell structures, palladium-based catalysts, metal oxides and chalcogenides, carbon-based non-noble metal catalysts and metal-free catalysts.
Abstract: The recent advances in electrocatalysis for oxygen reduction reaction (ORR) for proton exchange membrane fuel cells (PEMFCs) are thoroughly reviewed. This comprehensive Review focuses on the low- and non-platinum electrocatalysts including advanced platinum alloys, core–shell structures, palladium-based catalysts, metal oxides and chalcogenides, carbon-based non-noble metal catalysts, and metal-free catalysts. The recent development of ORR electrocatalysts with novel structures and compositions is highlighted. The understandings of the correlation between the activity and the shape, size, composition, and synthesis method are summarized. For the carbon-based materials, their performance and stability in fuel cells and comparisons with those of platinum are documented. The research directions as well as perspectives on the further development of more active and less expensive electrocatalysts are provided.

2,964 citations

Journal ArticleDOI
TL;DR: In this paper, the fundamental mechanism of heterogeneous photocatalysis, advantages, challenges and the design considerations of g-C3N4-based photocatalysts are summarized, including their crystal structural, surface phisicochemical, stability, optical, adsorption, electrochemical, photoelectrochemical and electronic properties.

2,132 citations

Journal ArticleDOI
Richard M. Crooks1, Mingqi Zhao1, Li Sun1, Victor Chechik1, Lee K. Yeung1 
TL;DR: Intradendrimer hydrogenation and carbon-carbon coupling reactions in water, organic solvents, biphasic fluorous/organic solvent, and supercritical CO2 are also described.
Abstract: This Account reports the synthesis and characterization of dendrimer-encapsulated metal nanoparticles and their applications to catalysis. These materials are prepared by sequestering metal ions within dendrimers followed by chemical reduction to yield the corresponding zerovalent metal nanoparticle. The size of such particles depends on the number of metal ions initially loaded into the dendrimer. Intradendrimer hydrogenation and carbon−carbon coupling reactions in water, organic solvents, biphasic fluorous/organic solvents, and supercritical CO2 are also described.

1,925 citations

Journal ArticleDOI
TL;DR: The definition and scope of hemilabile ligands are recalled, the main classes of ligands containing one or more oxazoline moieties are presented, with an emphasis on hybrid ligands, and why the combination of these two facets of ligand design appears particularly promising are explained.
Abstract: Ligand design is becoming an increasingly important part of the synthetic activity in chemistry. This is of course because of the subtle control that ligands exert on the metal center to which they are coordinated. Ligands which contain significantly different chemical functionalities, such as hard and soft donors, are often called hybrid ligands and find increasing use in molecular chemistry. Although the interplay between electronic and steric properties has long been recognized as essential in determining the chemical or physical properties of a complex, predictions remain very difficult, not only because of the considerable diversity encountered within the Periodic Table-different metal centers will behave differently towards the same ligand and different ligands can completely modify the chemistry of a given metal-but also because of the small energy differences involved. New systems may-even through serendipity-allow the emergence of useful concepts that can gain general acceptance and help design molecular structures orientated towards a given property. The concept of ligand hemilability, which finds numerous illustrations with hybrid ligands, has gained increased acceptance and been found to be very useful in explaining the properties of metal complexes and in designing new systems for molecular activation, homogeneous catalysis, functional materials, or small-molecule sensing. In the field of homogeneous enantioselective catalysis, in which steric and/or electronic control of a metal-mediated process must occur in such a way that one stereoisomer is preferentially formed, ligands containing one or more chiral oxazoline units have been found to be very valuable for a wide range of metal-catalyzed reactions. The incorporation of oxazoline moieties in multifunctional ligands of increasing complexity makes such ligands good candidates to display hemilabile properties, which until recently, had not been documented in oxazoline chemistry. Herein, we briefly recall the definition and scope of hemilabile ligands, present the main classes of ligands containing one or more oxazoline moieties, with an emphasis on hybrid ligands, and finally explain why the combination of these two facets of ligand design appears particularly promising.

839 citations

Journal ArticleDOI
TL;DR: The resultant POMC with a small amount of P doping is demonstrated as a metal-free electrode with excellent electrocatalytic activity for oxygen reduction reaction (ORR), coupled with much enhanced stability and alcohol tolerance compared to those of platinum via four-electron pathway in alkaline medium.
Abstract: Phosphorus-doped ordered mesoporous carbons (POMCs) with different lengths were synthesized using a metal-free nanocasting method of SBA-15 mesoporous silica with different sizes as template and triphenylphosphine and phenol as phosphorus and carbon sources, respectively. The resultant POMC with a small amount of P doping is demonstrated as a metal-free electrode with excellent electrocatalytic activity for oxygen reduction reaction (ORR), coupled with much enhanced stability and alcohol tolerance compared to those of platinum via four-electron pathway in alkaline medium. Interestingly, the POMC with short channel length is found to have superior electrochemical performances compared to those with longer sizes.

834 citations