Effects of Impurities on Pre-Doped and Post-Doped Membranes for High Temperature PEM Fuel Cell Stacks
, Sobi Thomas 2, Andrej Lotrič 3,4, Simon Lennart Sahlin 1, Vincenzo Liso 1 and Søren Juhl Andreasen 4Round 1
Reviewer 1 Report
In the introduction I suggest to explain also the applications of the fuel cell under study, for example take into account also the following papers:
Ferraris A., Messana A., Airale A.G., Sisca L., de Carvalho Pinheiro H., Zevola F., Carello M., “Nafion Tubing Humidification System for Polymer Electrolyte Membrane Fuel Cells”, Energies, 2019, 12, 1773 pages 16; doi:10.3390/en12091773.
Carello M; De Vita A.; Ferraris A., “Method for Increasing the Humidity in Polymer ElectrolyteMembrane” Fuel Cell, FUEL CELLS, WILEY-VCH Verlag GmbH & Co. KGaA,Weinheim, pp. 8, 2016, ISSN: 1615-6854, DOI: 10.1002/fuce.201500110.
In paragraph 2.1: it is possible to add more information about the MEA?
In paragraph 2.2: Test procedure: I suggest to add a scheme of the test bench and improuve the description of the test methodology (i.e. measured parameters)
In figure 4, Figure 6 and Figure 8 it is better to indicate Fuel Cell voltage…. (y-axis) e not Cell voltage…
Figure 5, Figure 7 and figure 9: explain better inside the test the meaning of hx
Line 386 1 kHz and not 1 KHz
In the conclusions I suggest to compare in terms of % the difference between the two experimental tests
If they are available please include some results of original stack (without nitrogen dilution and reformate impurities) because it is very important to observe the changing of the characteristics.
Explain how in real use of the fuel cell the nitrogen dilution and reformate impurities could be present.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This is a rather dull manuscript that describes experiments conducted with two High Temperature PEM fuel cell stacks containing different Membrane Electrode Assemblies. Performances of the stacks were monitored by voltammetry and Electrochemical Impedance Spectroscopy (EIS). Influence of fuel composition (pure H2, H2+N2, reformate, wet reformate) on voltammetry and impedance spectra was observed and analyzed.
EIS spectra were fitted by arbitrarily chosen equivalent circuit consisting of in series ohmic resistance, and three different R//CPE subcircuits. These “high frequency resistance HFR”, “intermediate frequency resistance (IFR)” and “low frequency resistance (LFR)” were ascribed to charge transfer resistances at the anode (HFR), charge transfer resistances at the cathode (IFR) and mass transport limitations (LFR). Apparently, these resistance elements were called by fractions of spectra in which influence of respective R//CPE subcircuits was most pronounced. EIS measurements were analyzed by Distribution of Relaxation Times (DRT) analysis, also.
There are no actual flaws in this manuscript. However, there is no scientific novelty in it. Influence of reformate composition on performance of HT PEMFCs is known for rather long time. Most of the manuscript is devoted to dependences of IFR, HFR, and LFR on the anode feed composition. No attempt to reveal physical chemistry behind was undertaken. This manuscript looks more like a technical paper.
One stack performed slightly better than the other. The reason for it is not discussed.
Results are discussed mostly in terms of dependences of these particular resistance elements, or characteristic relaxation times, on the anode fuel supply mode. Fitting of the EIS spectra is not discussed. Alternative equivalent schemes were not considered. Constant phase elements (CPE) were ignored in analysis completely. Frequency labels on Nyquist plots are not provided.
According to second line in Table shown in page 14 (here results are summarized), fuel composition influences IRF magnitude. However, IRF was ascribed to charge transfer resistance of oxygen reduction at the cathode. So it cannot be influenced by the fuel composition. Th observed influence of fuel composition on IRF value undermines the basic concept of the manuscript.
There are few misprints in the manuscript.
- line 149- “repeat uni of PBI”
- lines 189, 299, 308, 341, 397, 478. Nyquist plots are written as “nyquist”, “Nyquist” and “Nquist” plots.
- There two tables in the manuscript. Both of them are numbered as Table 1.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
I believe that in the present state the revised manuscript can be accepted for publication in the Journal.
