scholarly journals PEM Single Cells under Differential Conditions: Full Factorial Parameterization of the ORR and HOR Kinetics and Loss Analysis

2021 ◽  
Author(s):  
Christophe Gerling ◽  
Matthias Hanauer ◽  
Ulrich Berner ◽  
Kaspar Andreas Friedrich
Keyword(s):  
Steady State ◽  
Electrochemical Impedance ◽  
Hydrogen Oxidation ◽  
Single Cells ◽  
Reduction Reaction ◽  
Limiting Current ◽  
Hydrogen Oxidation Reaction ◽  
Wide Range ◽  
Current Densities ◽  
Full Factorial

Abstract The anode and cathode kinetics are parameterized based on differential cell measurements. Systematic parameter variations are evaluated to disentangle the dependencies of the electrochemical impedance spectroscopy (EIS) signatures in H2/H2 mode. We introduce a new CO recovery protocol for both electrodes that enables to accurately characterize the hydrogen oxidation reaction (HOR) kinetics. Then, we demonstrate that a compact Tafel kinetics law captures the oxygen reduction reaction (ORR) kinetics for a full factorial grid of conditions, covering a wide range of relative humidities (rH), temperatures, oxygen partial pressures and current densities. This yields the characteristic activation energy and effective reaction order, and we reconcile models that make different assumptions regarding the rH dependency. Moreover, we analyze O2 transport contributions by steady-state and transient limiting current techniques and heliox measurements. Although the rising uncertainty of loss corrections at high current densities makes it impossible to unambiguously identify an intrinsic potential-dependent change of the Tafel slope, our data support that such effect needs not be considered for steady-state cathodic half-cell potentials above 0.8 V.

Compact and efficient gas diffusion electrodes based on nanoporous alumina membranes for microfuel cells and gas sensors

The Analyst ◽  
2020 ◽  
Vol 145 (1) ◽  
pp. 122-131 ◽  
Author(s):  
Wanda V. Fernandez ◽  
Rocío T. Tosello ◽  
José L. Fernández
Keyword(s):  
Response Times ◽  
Hydrogen Oxidation ◽  
Fast Response ◽  
Gas Diffusion ◽  
Limiting Current ◽  
Gas Diffusion Electrodes ◽  
Nanoporous Alumina ◽  
Alumina Membranes ◽  
Current Densities ◽  
Microfuel Cells

Gas diffusion electrodes based on nanoporous alumina membranes electrocatalyze hydrogen oxidation at high diffusion-limiting current densities with fast response times.

Testing of solid oxide cells at high current densities

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
André Weber
Keyword(s):  
Single Cell ◽  
High Performance ◽  
High Efficiency ◽  
Electrochemical Impedance ◽  
Single Cells ◽  
Operating Conditions ◽  
Solid Oxide ◽  
Current Densities ◽  
Cell Testing ◽  
The Impact

Abstract Solid Oxide Cells (SOCs) have gained an increasing interest as electrochemical energy converters due to their high efficiency, fuel flexibility and ability of reversible fuel cell/electrolysis operation. During the development process as well as in quality assurance tests, the performance of single cells and cell stacks is commonly evaluated by means of current/voltage- (CV-) characteristics. Despite of the fact that the measurement of a CV-characteristic seems to be simple compared to more complex, dynamic methods as electrochemical impedance spectroscopy or current interrupt techniques, the resulting performance strongly depends on the test setup and the chosen operating conditions. In this paper, the impact of different single cell testing environments and operating conditions on the CV-characteristic of high performance cells is discussed. The influence of cell size, contacting and current collection, contact pressure, fuel flow rate and composition on the achievable cell performance is presented and limitations arising from the test bed and testing conditions will be pointed out. As today’s high performance cells are capable of delivering current densities of several ampere per cm2 a special emphasis will be laid on single cell testing in this current range.

Micron-Scale Diagnostics for Through-Plane Transport Phenomena in Porous Electrodes

2010 ◽  
Author(s):  
Katherine C. Hess ◽  
William K. Epting ◽  
Shawn Litster
Keyword(s):  
Hydrogen Oxidation ◽  
Polymer Electrolyte Membrane ◽  
Transport Phenomena ◽  
Reduction Reaction ◽  
Porous Electrodes ◽  
New Method ◽  
Hydrogen Oxidation Reaction ◽  
Electrolyte Membrane ◽  
Microstructured Electrode ◽  
Accuracy And Repeatability

This paper presents the development of a new method for characterizing the electrochemistry and transport phenomena in the porous electrodes of polymer electrolyte membrane fuel cells (PEMFCs). The new method uses a unique microstructured electrode scaffold (MES) that provide an architecture for obtaining measurements at discrete points through the thickness of an electrode. This paper reports on the design, fabrication and initial testing of an MES for measuring ionic potential across the thickness of a PEMFC’s cathode. The new fuel cell hardware and reference electrodes (REs), which gather electrolyte potential measurements through the thickness of the electrode via the MES, have been tested for accuracy and repeatability. The use of hydrogen oxidation reaction (HOR) REs versus oxygen reduction reaction (ORR) REs is analyzed and discussed. Polarization data was also gathered and the REs are used to separate the half-cell potentials. Finally, the preliminary fabrication of an MES and a micro-structural analysis are discussed.

Study of IrxMny(CO)n(DMF)z as Electrocatalyst for Oxygen Reduction and Hydrogen Oxidation in the Presence of Fuel Cell Contaminants

2016 ◽  
Vol 19 (4) ◽  
pp. 185-192 ◽  
Author(s):  
M.L. Barrios-Reyna ◽  
J. Uribe-Godínez ◽  
J.M. Olivares-Ramírez ◽  
O. Jiménez-Sandoval
Keyword(s):  
Oxygen Reduction ◽  
Hydrogen Oxidation ◽  
Rotating Disk ◽  
Pem Fuel Cells ◽  
Platinum Group Metals ◽  
The Novel ◽  
Hydrogen Oxidation Reaction ◽  
Acid Media ◽  
X Ray ◽  
Wide Range

The oxygen reduction reaction (ORR) and the hydrogen oxidation reaction (HOR) have been studied on a wide range of elec-trocatalysts, including bimetallic materials which are based solely on platinum group metals and their alloys. This work reports the synthe-sis and characterization of a novel bimetallic electrocatalyst, IrxMny(CO)n(DMF)z, for the ORR and HOR in acid media. The material was synthesized by reacting Ir4(CO)12 and MnCl2·4H2O in DMF. It was characterized structurally by FT-IR and micro-Raman spectroscopy, X-ray diffraction, SEM and energy-dispersive X-ray spectroscopy; the electrochemical characterization was made by the rotating disk elec-trode technique, at room temperature. The electrocatalytic activity of the new material for the ORR and HOR does not show appreciable variations due to the presence of methanol or carbon monoxide, respectively, even at high concentrations of these contaminants (2 mol L-1 methanol and 0.5% CO). This tolerance is a very important property with respect to platinum-based catalysts, which are poisoned by low concentrations of such contaminants. The kinetic parameters of the novel catalyst, such as Tafel slope (b), exchange current density (jo) and charge transfer coefficient (α), are reported as well. The results show that the novel electrocatalyst is attractive for evaluation as cath-ode/anode in PEM fuel cells.

Processing of Raney-Nickel Catalysts for Alkaline Fuel Cell Applications

2006 ◽  
Vol 4 (1) ◽  
pp. 45-48 ◽  
Author(s):  
J. A. Linnekoski ◽  
A. O. I. Krause ◽  
Jari Keskinen ◽  
J. Lamminen ◽  
T. Anttila
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Raney Nickel ◽  
Hydrogen Oxidation ◽  
Catalyst Layer ◽  
Nickel Catalysts ◽  
Alkaline Fuel Cell ◽  
Hydrogen Oxidation Reaction ◽  
Raney Nickel Catalyst ◽  
Current Densities

Platinum and other platinum group metals, either as singles or in combinations, have been preferred for use in low temperature fuel cells, mainly alkaline fuel cells (AFCs), polymer membrane electrolyte fuel cells (PEMs), and direct methanol fuel cells (DMFCs), for hydrogen oxidation reaction (HOR). However, also the Raney-nickel catalyst, which is among the most active non-noble metals for the HOR, has been the target of interest, especially in AFCs. However, electrodes with nonsupport Raney-nickel catalysts have been reported to suffer from insufficient conductivity. So, in this work, in order to enhance the electrical conductivity in the catalyst layer and to increase the catalytic activity, the Raney-nickel catalysts were alloyed with carbon in a planetary-type ball mill. In some samples platinum was added chemically to still enhance the catalytic properties. The activity of the processed materials was tested in the anode reaction of the alkaline fuel cell by measuring the half-cell polarization curves. It was found that the effective mixing of Raney-nickel powder and carbon in the ball mill was beneficial compared with poorer mixing in the knife mill. However, in order to achieve the same current densities at the same polarization level as the commercial Pt catalyst (2mg∕cm2), much higher Raney-nickel contents (73mg∕cm2) were needed. Good contact between Raney-nickel and conductive material (carbon) in the catalyst layer of the alkaline fuel cell electrode can improve the performance of the Raney-nickel catalyst in the hydrogen oxidation reaction. The polarization was lowered especially at the higher current densities (>250mA∕cm2).

scholarly journals Ανάπτυξη διμεταλλικών ηλεκτροκαταλυτών για εφαρμογή σε στοιχεία καυσίμου χαμηλής θερμοκρασίας

2020 ◽  
Author(s):  
Γεώργιος Μπάμπος
Keyword(s):  
Thin Film ◽  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Oxidation Reaction ◽  
Hydrogen Oxidation ◽  
Reduction Reaction ◽  
Hydrogen Oxidation Reaction ◽  
Rotating Electrode ◽  
Electrode Technique

Στην παρούσα εργασία έγινε μελέτη νέων διμεταλλικών ηλεκτροκαταλυτών για την ηλεκτροχημική αντίδραση της αναγωγής του Ο2 (Oxygen reduction reaction, ORR) και την ηλεκτροχημική αντίδραση της οξείδωσης του Η2 (Hydrogen oxidation reaction, HOR) σε όξινο και αλκαλικό περιβάλλον, η οποία πραγματοποιήθηκε κύρια με την τεχνική του ηλεκτροδίου περιστρεφόμενου δίσκου με τον ηλεκτροκαταλύτη ως εναπόθεμα μικρού πάχους (thin-film rotating electrode technique, RDE). Πιο συγκεκριμένα, μελετήθηκε η δραστικότητα ως προς ORR, τόσο σε διάλυμα 0.1M HClO4 όσο και σε διάλυμα 0.1Μ ΚΟΗ, βασισμένων σε Pd διμεταλλικών ηλεκτροκαταλυτών 7.5 wt.% Pd – 2.5 wt.% M στηριγμένων σε αγώγιμο άνθρακα (Vulcan XC72R) οι οποίοι παρασκευάστηκαν κύρια με τη μέθοδο του υγρού εμποτισμού και υπέστησαν αναγωγή υπό ροή Η2 στους 300 oC. Οι ηλεκτροκαταλύτες αυτοί μελετήθηκαν επίσης όσον αφορά στη δραστικότητά τους ως προς ΗΟR σε διάλυμα 0.1Μ HClO4 αλλά και σε διάλυμα 0.1Μ ΚΟΗ. Οι ηλεκτροκαταλυτικές σκόνες χαρακτηρίστηκαν φυσικοχημικά με φυσική ρόφηση (ΒΕΤ), XRD, TEM, SEM και XPS. Σε όλες τις περιπτώσεις, έγινε σύγκριση της δραστικότητας των βασισμένων σε Pd ηλεκτροκαταλυτών με εκείνη ηλεκτροκαταλυτών Pt ίδιας συνολικής μεταλλικής φόρτισης. Η αναλογία Pd:M και η θερμοκρασία αναγωγής που χρησιμοποιήθηκαν ήταν οι βέλτιστες από άποψη δραστικότητας, όπως προέκυψε από σχετικά πειράματα αριστοποίησης που έγιναν με τους δραστικότερους για κάθε μελετηθείσα αντίδραση διμεταλλικούς ηλεκτροκαταλύτες. Για κάθε διμεταλλικό σύστημα Pd-M με την μεγαλύτερη δραστικότητα κατά περίπτωση (με μεταλλική φόρτιση 10 wt.%), παρασκευάστηκαν με τη μέθοδο του υγρού εμποτισμού ηλεκτροκαταλύτες ίδιας αναλογίας Pd:Μ και θερμοκρασίας αναγωγής αλλά υψηλότερης μεταλλικής φόρτισης (29 wt.%) των οποίων η δραστικότητα συγκρίθηκε με εκείνη ηλεκτροκαταλυτών Pt ίδιας μεταλλικής φόρτισης. Οι ηλεκτροκαταλύτες με μεταλλική φόρτιση 29 wt.% μελετήθηκαν και ως προς τη σταθερότητά τους. Στην περίπτωση της μελέτης της ORR σε όξινο περιβάλλον και για το δραστικότερο διμεταλλικό σύστημα μελετήθηκε και η επίδραση στη δραστικότητα της μεθόδου σύνθεσης αλλά και του φορέα. Επίσης, στην περίπτωση της ORR σε 0.1Μ ΗClO4, μελετήθηκε και μία σειρά στηριγμένων σε Vulcan XC72R ηλεκτροκαταλυτών 10 wt.% Pt – M (Μ: Ag, Cu, Fe, Ni, Sn, Zn) όσον αφορά τη δραστικότητά τους απουσία και παρουσία αιθανόλης. Τέλος, ο δραστικότερος ως προς ORR σε όξινο περιβάλλον διμεταλλικός ηλεκτροκαταλύτης 22 wt.% Pd – 7 wt.% Zn/C μελετήθηκε ως καθοδικό ηλεκτρόδιο στοιχείου καυσίμου τύπου PEM τροφοδοτούμενου με Η2, του οποίου η απόδοση συγκρίθηκε με εκείνη του ίδιου στοιχείου καυσίμου με κάθοδο βασισμένη σε ηλεκτροκαταλύτες Pt.

scholarly journals Bimetallic nickel-molybdenum/tungsten nanoalloys for high-efficiency hydrogen oxidation catalysis in alkaline electrolytes

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Yu Duan ◽  
Zi-You Yu ◽  
Li Yang ◽  
Li-Rong Zheng ◽  
Chu-Tian Zhang ◽  
...  
Keyword(s):  
High Efficiency ◽  
Hydrogen Oxidation ◽  
Carbon Monoxide Poisoning ◽  
Platinum Group Metal ◽  
Reduction Reaction ◽  
Oxidation Catalysis ◽  
Hydrogen Oxidation Reaction ◽  
Group Metal ◽  
Alkaline Electrolytes ◽  
Platinum Group

Abstract Hydroxide exchange membrane fuel cells offer possibility of adopting platinum-group-metal-free catalysts to negotiate sluggish oxygen reduction reaction. Unfortunately, the ultrafast hydrogen oxidation reaction (HOR) on platinum decreases at least two orders of magnitude by switching the electrolytes from acid to base, causing high platinum-group-metal loadings. Here we show that a nickel-molybdenum nanoalloy with tetragonal MoNi4 phase can catalyze the HOR efficiently in alkaline electrolytes. The catalyst exhibits a high apparent exchange current density of 3.41 milliamperes per square centimeter and operates very stable, which is 1.4 times higher than that of state-of-the-art Pt/C catalyst. With this catalyst, we further demonstrate the capability to tolerate carbon monoxide poisoning. Marked HOR activity was also observed on similarly designed WNi4 catalyst. We attribute this remarkable HOR reactivity to an alloy effect that enables optimum adsorption of hydrogen on nickel and hydroxyl on molybdenum (tungsten), which synergistically promotes the Volmer reaction.

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