scispace - formally typeset
Search or ask a question
Author

Zenonas Jusys

Bio: Zenonas Jusys is an academic researcher from University of Ulm. The author has contributed to research in topics: Electrochemistry & Catalysis. The author has an hindex of 30, co-authored 108 publications receiving 2894 citations.


Papers
More filters
Journal ArticleDOI
TL;DR: Based on results, the addition of Sn or Ru, though beneficial for the overall activity for ethanol oxidation, does not enhance the activity for C-C bond breaking and the higher ethanol oxidation current density on the Pt3Sn/C catalyst at these potentials results from higher yields of C2 products, not from an improved complete ethanol oxidation to CO2.
Abstract: The interaction of colloid-based, carbon supported Pt/C (40 wt%), PtRu/C (45 wt%) and Pt3Sn/C (24 wt%) catalysts with ethanol and their performance for ethanol electrooxidation were investigated in model studies by electrochemical, in situ infrared spectroscopy and on-line differential electrochemical mass spectrometry measurements. The combined application of in situ spectroscopic techniques on realistic catalysts and under realistic reaction (DEMS, IR) and transport conditions (DEMS) yields new insight on mechanistic details of the reaction on these catalysts under the above reaction and transport conditions. Based on these results, the addition of Sn or Ru, though beneficial for the overall activity for ethanol oxidation, does not enhance the activity for C–C bond breaking. Dissociative adsorption of ethanol to form CO2 is more facile on the Pt/C catalyst than on PtRu/C and Pt3Sn/C catalysts within the potential range of technical interests (<0.6 V), but Pt/C is rapidly blocked by an inhibiting CO adlayer. In all cases acetaldehyde and acetic acid are dominant products, CO2 formation contributes less than 2% to the total current. The higher ethanol oxidation current density on the Pt3Sn/C catalyst at these potentials results from higher yields of C2 products, not from an improved complete ethanol oxidation to CO2.

155 citations

Journal ArticleDOI
TL;DR: The potential of in-situ Fourier transform infrared (FTIR) spectroscopy measurements in an attenuated total reflection configuration (ATR-FTIRS) for the evaluation of reaction pathways, elementary reaction steps, and their kinetics is demonstrated for formic acid electrooxidation on a Pt film electrode.
Abstract: The potential of in-situ Fourier transform infrared (FTIR) spectroscopy measurements in an attenuated total reflection configuration (ATR-FTIRS) for the evaluation of reaction pathways, elementary reaction steps, and their kinetics is demonstrated for formic acid electrooxidation on a Pt film electrode. Quantitative kinetic information on two elementary steps, formic acid dehydration and COad oxidation, and on the contributions of the related pathways in the dual path reaction mechanism are derived from IR spectroscopic signals in simultaneous electrochemical and ATR-FTIRS measurements over a wide temperature range (25−80 °C). Linearly and multiply bonded COad and bridge-bonded formate are the only formic acid related stable reaction intermediates detected. With increasing temperature, the steady-state IR signal of COad increases, while that of formate decreases. Reaction rates for COad formation via formic acid dehydration and for COad oxidation as well as the activation energies of these processes were ...

140 citations

Journal ArticleDOI
TL;DR: The determination of kinetic isotope effects (KIEs) for different reaction pathways and steps in a complex reaction network, where KIEs may affect the overall reaction in various different ways including dominant and minority pathways or the buildup of a reaction-inhibiting adlayer, is demonstrated.
Abstract: The determination of kinetic isotope effects (KIEs) for different reaction pathways and steps in a complex reaction network, where KIEs may affect the overall reaction in various different ways including dominant and minority pathways or the buildup of a reaction-inhibiting adlayer, is demonstrated for formic acid electrooxidation on a Pt film electrode by quantitative electrochemical in situ IR spectroscopic measurements under controlled mass-transport conditions. The ability to separate effects resulting from different contributions--which is not possible using purely electrochemical kinetic measurements--allows conclusions on the nature of the rate-limiting steps and their transition state in the individual reaction pathways. The potential-independent values of approximately 1.9 for the KIE of formic acid dehydration (CO(ad) formation) in the indirect pathway and approximately 3 for the CO(ad) coverage-normalized KIE of formic acid oxidation to CO2 (direct pathway) indicate that 1) C-H bond breaking is rate-limiting in both reaction steps, 2) the transition states for these reactions are different, and 3) the configurations of the transition states involve rather strong bonds to the transferred D/H species, either in the initial or in the final state, for the direct pathway and--even more pronounced--for formic acid dehydration (CO(ad) formation).

103 citations

Journal ArticleDOI
TL;DR: In this article, a combination of in situ attenuated total reflection-infrared spectroscopy (ATR-FTIRS) and on-line differential electrochemical mass spectrometry (DEMS) via a dual thin-layer electrochemical flow-cell is presented.

102 citations

Journal ArticleDOI
TL;DR: In this article, the results of a differential electrochemical mass spectrometry study on the electrooxidation of CO and H2/CO mixtures on a high surface area carbon-supported Pt/Vulcan catalyst were reported.
Abstract: We report the results of a differential electrochemical mass spectrometry study on the electrooxidation of CO and H2/CO mixtures on a high surface area carbon-supported Pt/Vulcan catalyst. The measurements were performed in a thin-layer flow-cell, allowing the quantitative determination of the individual reaction rates under controlled mass transport conditions as a function of the electrode potential, parallel to the Faraday current. COad monolayer oxidation (stripping) experiments in a 0.5 M H2SO4 solution saturated with H2 or with 2% CO in H2 show that (i) the hydrogen oxidation reaction (HOR) in CO-free, H2-saturated solution starts already at potentials right at the onset of CO oxidation (0.15 VRHE), as evidenced by the simultaneous increase in Faraday current, the increase in the CO2 signal, and the decrease in H2 content in the solution, and that (ii) in CO containing solution the onset of the HOR is shifted to more positive potentials due to continuous CO readsorption. In the former case 90% of the mass transport limited current is reached already at a potential where only ∽5% of the saturated CO adlayer is oxidized, in the latter case the limiting HOR current is reached only in the potential regime of the main CO stripping peak. Furthermore, in the second case CO oxidation in the pre-wave regime is enhanced, while the HOR is suppressed in this potential regime compared to CO stripping in CO-free H2-saturated electrolyte. As a result the ignition of the HOR in the H2/CO(2%) saturated electrolyte occurs only together with the main CO oxidation peak. The data are direct proof that the HOR proceeds in an almost closed CO adlayer, most likely in small (fluctuating) holes of the adlayer and has to compete with CO readsorption. Kinetic measurements at constant electrode potential (0.04 V) in H2/CO(2%)-saturated solution show that CO adsorption from an H2/CO mixture follows a precursor-type adsorption kinetics. For the HOR the data show substantial deviations from both a (1 − θCO) and (1 − θCO)2 dependence of the HOR rate on the CO coverage, pointing to a more complex mechanism than a simple site-blocking mechanism.

96 citations


Cited by
More filters
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
Tamar Frankel1
TL;DR: The Essay concludes that practitioners theorize, and theorists practice, use these intellectual tools differently because the goals and orientations of theorists and practitioners, and the constraints under which they act, differ.
Abstract: Much has been written about theory and practice in the law, and the tension between practitioners and theorists. Judges do not cite theoretical articles often; they rarely "apply" theories to particular cases. These arguments are not revisited. Instead the Essay explores the working and interaction of theory and practice, practitioners and theorists. The Essay starts with a story about solving a legal issue using our intellectual tools - theory, practice, and their progenies: experience and "gut." Next the Essay elaborates on the nature of theory, practice, experience and "gut." The third part of the Essay discusses theories that are helpful to practitioners and those that are less helpful. The Essay concludes that practitioners theorize, and theorists practice. They use these intellectual tools differently because the goals and orientations of theorists and practitioners, and the constraints under which they act, differ. Theory, practice, experience and "gut" help us think, remember, decide and create. They complement each other like the two sides of the same coin: distinct but inseparable.

2,077 citations

Journal ArticleDOI
TL;DR: In this paper, an up-to-date perspective on the use of anion-exchange membranes in fuel cells, electrolysers, redox flow batteries, reverse electrodialysis cells, and bioelectrochemical systems (e.g. microbial fuel cells).
Abstract: This article provides an up-to-date perspective on the use of anion-exchange membranes in fuel cells, electrolysers, redox flow batteries, reverse electrodialysis cells, and bioelectrochemical systems (e.g. microbial fuel cells). The aim is to highlight key concepts, misconceptions, the current state-of-the-art, technological and scientific limitations, and the future challenges (research priorities) related to the use of anion-exchange membranes in these energy technologies. All the references that the authors deemed relevant, and were available on the web by the manuscript submission date (30th April 2014), are included.

1,526 citations

Journal ArticleDOI
TL;DR: Increasing research efforts are carried out to design and develop more efficient anode electrocatalysts for DAFCs, which are attracting increasing interest as power sources for portable applications.
Abstract: Direct alcohol fuel cells (DAFCs) are attracting increasing interest as power sources for portable applications due to some unquestionable advantages over analogous devices fed with hydrogen.1 Alcohols, such as methanol, ethanol, ethylene glycol, and glycerol, exhibit high volumetric energy density, and their storage and transport are much easier as compared to hydrogen. On the other hand, the oxidation kinetics of any alcohol are much slower and still H2-fueled polymer electrolyte fuel cells (PEMFCs) exhibit superior electrical performance as compared to DAFCs with comparable electroactive surface areas.2,3 Increasing research efforts are therefore being carried out to design and develop more efficient anode electrocatalysts for DAFCs.

1,427 citations