Tuning the Surface Oxophilicity of PdAu Alloy Nanoparticles to Favor Electrochemical Reactions: Hydrogen Oxidation and Oxygen Reduction in Anion Exchange Membrane Fuel Cells

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This publication on AEMFC investigates the influence of the surface chemistry of PdAu alloy-based catalysts. In line 41, the authors refer to the use of more sustainable and abundant metals; however, just one line later, they mention the use of palladium and platinum. Yet, palladium is just as expensive as platinum.

In paragraph 2, it is unfortunate that the diffractograms in Figure 1 are not more extensively analyzed. Would it be possible to calculate the crystallite sizes? It would also be interesting to correlate these XRD results with HR-TEM data to provide both a local and global comparison of these characteristics. It is also surprising to compare ICP data with a method as localized as HR-TEM. By the way, was the EDS analysis performed on several nanoparticles?

For Figure 5, a clear legend is missing that would indicate the experimental points and the fitting. It is also surprising that the entire study's conclusions are based solely on XPS analysis. Did you perform elemental analysis and TGA to validate the measured oxygen percentage?

In the electrochemical section, the experimental protocol is relatively well described, except for the deposition protocol on the rotating electrode. What is the composition of the ink, how is it deposited, and what is the amount of catalyst and ionomer used? Is the Ag/AgCl reference electrode the most suitable for this setup? Could the gold counter electrode introduce contamination or artifacts into the measurements? How many MEA have you characterized? It would be interesting to add error bar. Regarding Figure 6d, the purple curve shows a peak: is this an artefact, or is there an explanation for it? For Figure 8A, what are your hypotheses regarding mass transport limitations? It would be interesting to formulate hypotheses and attempt to understand these limitations.

Lastly, in terms of presentation, the tables do not integrate well with the text.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

In this manuscript, the authors reported a facile heat treatment approach to tune the crystallinity and oxophilicity of PdAu alloy nanoparticles, leading to much enhanced electrocatalytic performance toward the hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR) under alkaline condition and in an anion exchange membrane fuel cell (AEMFC). Overall, this is very novel research and the results were clearly presented. I would generally support the publication at the journal Catalysts. However, to further enhance clarity and quality of the current manuscript, the below detailed comments need to be properly addressed. I hope the authors find the comments useful in improving the manuscript.

1. The authors wanted to highlight the importance of tuning Surface Oxophilicity of PdAu on the HOR and ORR performance. However, there is not much evidence on how the Surface Oxophilicity was tuned. There is no much mentioning of the key work “oxophilicity”. Please provide more evidence or discussion to support this claim.
2. To appeal to a broader readership, recent works on fuel cells and ORR catalysis can be referenced (doi: 10.1002/inf2.12608; doi: 10.1039/D0MH00477D).
3. CVs were recorded at a rate of 20 mV s-1 to calculate the electrochemical active surface area (EASA). How exactly was the EASA calculated? Please provide more details on this.
4. Figure 8, the power curves (black line) and potential scan (dotted line) at Tcell=60 °C appear to be very different from those at Tcell=80 °C. Please explain this inconsistency.

Author Response

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Author Response File: Author Response.pdf