Papers by Claudio Zafferoni
Bimetallic catalysts for ORR and EOR
Fe-Co-N-C catalyst for oxygen reduction reaction derived from SBA-15 templated polypyrrole. Performance in acidic and alkaline conditions
FeCo-N-C electrocatalyst produced by polymerization of polypyrrole and SBA15 for the ORR under alkaline conditions
Bimetallic catalysts and metal-free catalysts for ORR
ChemElectroChem, 2018
Alkaline Membrane Fuel Cells (AMFCs), have started to become more attractive in recent years due ... more Alkaline Membrane Fuel Cells (AMFCs), have started to become more attractive in recent years due to the development of polymeric membranes with good anionic conductivity and durability. However, few studies investigating the performance of H2/O2 fuelled AMFCs and alkaline Direct Ethanol Fuel Cells (DEFCs) with membrane electrode assemblies (MEAs) fabricated with Pt-group metal (PGM) free catalysts are available in the literature. In this paper, we synthesised and fully characterized a Fe-CoN -C electrocatalyst for oxygen reduction reaction (ORR) by sacrificial method, using pyrrole as a unique and cheap precursor of the N-doped carbonaceous material. A very good ORR activity and stability was obtained in alkaline conditions, most likely due to the presence of Co-Fe@C nanoparticles. We achieved a very high performance in AMFC, 420 mW cm-2 at 60 °C, among the highest in the literature for PGMfree catalysts, and a good performance in passive DEFC, 28 mW cm-2 at room temperature.
Electrochemical Underpotential Codeposition of MnS Thin Films for Photovoltaic Applications
Journal of The Electrochemical Society, 2016
Catalysis Science & Technology, 2016
Two different synthetic approaches to carbon nanotube N-decoration/doping are used to foster the ... more Two different synthetic approaches to carbon nanotube N-decoration/doping are used to foster the hypothesis of a unique N-configuration (N-pyridinic) at work in the ORR.
Molecules (Basel, Switzerland), Jan 7, 2015
The combination of two different metals, each of them acting on different steps of the oxygen red... more The combination of two different metals, each of them acting on different steps of the oxygen reduction reaction (ORR), yields synergic catalytic effects. In this respect, the electrocatalytic effect of silver is enhanced by the addition of cobalt, which is able to break the O-O bond of molecular oxygen, thus accelerating the first step of the reduction mechanism. At the same time, research is to further reduce the catalyst's cost, reducing the amount of Ag, which, even though being much less expensive than Pt, is still a noble metal. From this point of view, using a small amount of Ag together with an inexpensive material, such as graphite, represents a good compromise. The aim of this work was to verify if the synergic effects are still operating when very small amounts of cobalt (2-10 μg·cm(-2)) are added to the microparticles of silver electrodeposited on glassy carbon, described in a preceding paper from us. To better stress the different behaviour observed when cobalt and ...
Journal of Power Sources, 2015
PdeCo catalysts were electrodeposited with compositions between 20 and 80 at% Co. A transformatio... more PdeCo catalysts were electrodeposited with compositions between 20 and 80 at% Co. A transformation of alloyed Co to CoOOH/Co 3 O 4 flakes was observed after cycling. The Co in the films supplies eOH to EtOH oxidation, reducing onset potential. A max peak current density is found at an optimum composition of 77 at% Co. A 50 at% CoePd film exhibited the highest stable currents among PdeCo alloys.
Electrochimica Acta, 2015
Deactivation is one the main causes still preventing the full exploitation of palladium electroca... more Deactivation is one the main causes still preventing the full exploitation of palladium electrocatalysts in alkaline direct alcohol fuel cells and the electrochemical reforming of alcohols. While often attributed to the adsorption of poisoning species generated in the alcohols oxidation, in the present work we demonstrate that deactivation is provoked by the formation of palladium oxides. A combined approach including i) fuel cell runs, ii) cyclic voltammetry and iii) near edge X-ray absorption spectroscopy has enabled us to draw the conclusions reported in the paper.
ACS Catalysis, 2013
A straightforward, energy-and atom-saving process to the production of tailored N-doped and catal... more A straightforward, energy-and atom-saving process to the production of tailored N-doped and catalytically active metal-free carbon nanostructures, has been set up. Our ex situ approach to the N-decoration of the carbon nanotube sidewalls contributes to elucidate the complex structure−reactivity relationship of N-doped carbon nanomaterials in oxygen reduction reactions, providing fundamental insights on the nature of the N-active sites as well as on the role of neighboring carbons.
Journal of Power Sources, 2013
We obtain new Pt-free catalytic surfaces for the oxygen reduction reaction (ORR). We use metals s... more We obtain new Pt-free catalytic surfaces for the oxygen reduction reaction (ORR). We use metals such as FeeCoeAg which are suitable for alkaline fuel cells. We apply the SEBALD method to deposit clusters of Fe and Co on silver. Increasing information about three-metallic electrocatalysts.
Electroactivation of Microparticles of Silver on Glassy Carbon for Oxygen Reduction and Oxidation Reactions
Journal of The Electrochemical Society, 2014
ABSTRACT The electrocatalytic properties of small amounts of silver (3-17 mu g cm(-2)) electrodep... more ABSTRACT The electrocatalytic properties of small amounts of silver (3-17 mu g cm(-2)) electrodeposited on glassy carbon can be sensibly increased by an activation protocol based on pretreatment oxidation/reduction Cycles that produces significant changes in particle's morphology. The catalytic effects on both Oxygen Evolution Reaction (OER) and Oxygen Reduction Reaction (ORR) are evaluated by the onset potentials of the voltammetric curves, and the number of electrons involved in ORR is evaluated by the Levich plot. Tafel plots of both OER and ORR curves obtained after the activation protocol show significant changes that rule out the hypothesis that the catalytic effect could only be attributed to an increased roughness of the samples. Furthermore, the electrochemically active surface area of silver, as measured by the charge involved in Pb underpotential deposition, was found to increase linearly with the amount of depositing silver. On the contrary, the Tafel plots of increasing amounts of silver show that the increase of the catalytic effect with silver loading is not linear as expected in a mere increase of the roughness factor. Levich-Koutecky and Tafel plots evidenced that the highest silver loading showed a catalytic effect greater than that expected on the basis of the electrochemically active surface area.
Chemistry of Materials, 2014
We report on the N-decoration of multiwalled carbon nanotubes (MWCNTs) via chemical functionaliza... more We report on the N-decoration of multiwalled carbon nanotubes (MWCNTs) via chemical functionalization under mild reaction conditions. The introduction of tailored pyridinic functionalities as N-containing edge-type group mimics generates effective catalysts for the oxygen reduction reaction (ORR) in an alkaline environment. The adopted methodology lists a number of remarkable technical advantages, among which is an easy tuning of the electronic properties of N-containing groups. The latter aspect further increases the level of complexity for the rationalization of the role of the N-functionalities on the ultimate electrochemical performance of the as-prepared metal-free catalysts. Electrochemical outcomes crossed with the computed electronic charge density distributions on each scrutinized pyridine group have evidenced the central role played by the N-chemical environment on the final catalyst performance. Notably, small variations of the atomic charges on the N-proximal carbon atoms of the chemically grafted heterocycles change the overpotential values at which the oxygen reduction reaction starts. The protocol described hereafter offers an excellent basis for the development of more active metal-free electrocatalysts for the ORR. Finally, the asprepared catalytically active materials represent a unique model for the in-depth understanding of the underlying ORR mechanism.
Underpotential Deposition of Sn on S-Covered Ag(111)
ECS Transactions, 2013
Tin sulfides present electrical and optical properties, which give them high potential use in opt... more Tin sulfides present electrical and optical properties, which give them high potential use in opto-electronic devices and photoconductive cells, i.e. photovoltaic applications. In this paper we report an electrochemical study of a tin solution, carried out by cyclic and stripping voltammetry. These techniques allow to establish the presence of surface limited processes and, hence, to define the experimental conditions for the Underpotential Deposition of Sn on Ag(111) previously covered by a S monolayer. Moreover, we studied the growth of the first layers of tin sulfides.
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Papers by Claudio Zafferoni