Enhancing catalytic performance of dilute metal alloy nanomaterials

Dilute alloys are promising materials for sustainable chemical production; however, their composition and structure affect their performance. Herein, a comprehensive study of the effects of pretreatment conditions on the materials properties of Pd0.04Au0.96 nanoparticles partially embedded in porous silica is related to the activity for catalytic hydrogenation of 1-hexyne to 1-hexene. A combination of in situ characterization and theoretical calculations provide evidence that changes in palladium surface content are induced by treatment in oxygen, hydrogen and carbon monoxide at various temperatures. In turn, there are changes in hydrogenation activity because surface palladium is necessary for H2 dissociation. These Pd0.04Au0.96 nanoparticles in the porous silica remain structurally intact under many cycles of activation and deactivation and are remarkably resistant to sintering, demonstrating that dilute alloy catalysts are highly dynamic systems that can be tuned and maintained in a active state.

I am happy that my comments have been addressed and the paper is now suitable for publication Reviewer #2 (Remarks to the Author): I am happy to see that the authors provide in situ EXAFS data to support their main conclusions. I am satisfied with most of the responses to the reviewers' concerns. The manuscript now presents improved quality and is suitable for publication.
Reviewer #3 (Remarks to the Author): This manuscript remains a very good characterization study. While I personally believe that the results are somewhat over-sold, researchers familiar with this reaction and bimetallic system will immediately recognize this and give the paper it's due attention. The clear characterization of the chemistry associated with Pd mobility make this a valuable contribution to the literature. It is appropriate for Chem Commun.
There is one relatively small change that should be made prior to publication. The manuscript claims that Pd is "more stable" in the bulk than on the surface; this is largely based on a 0.05 eV difference in the DFT slab calculations. While the data show that, indeed, the sub-surface Pd is 0.05 eV lower in energy, this difference remains within reasonable DFT errors and is therefore probably not significant. I can live with modifying these statements being modified to "slightly more stable".
The manuscript would also benefit from clarifying that the "slightly" is an important property of the system. It is only because the energy differences are small that the Pd-O bond energy is large enough to pull the Pd to the surface. Similarly, the Pd remains on the surface to do the catalysis (at least initially) after O removal BECAUSE there is only a weak driving force for it to migrate back into the bulk. The exchange is due to these small energy differences. If Pd was much more stable in the bulk, it would stay there during oxidation or it would likely migrate back quickly after O removal. Readers would benefit from having clear statements to this effect.

I am happy that my comments have been addressed and the paper is now suitable for publication
Response to reviewer #1: We thank the reviewer for the positive review. No changes to the manuscript were made.

Reviewer #2 (Remarks to the Author): I am happy to see that the authors provide in situ EXAFS data to support their main conclusions. I am satisfied with most of the responses to the reviewers' concerns. The manuscript now presents improved quality and is suitable for publication.
Response to reviewer #2: We thank the reviewer for the positive review. No changes to the manuscript were made.

Reviewer #3 (Remarks to the Author):
This manuscript remains a very good characterization study. While I personally believe that the results are somewhat over-sold, researchers familiar with this reaction and bimetallic system will immediately recognize this and give the paper it's due attention. The clear characterization of the chemistry associated with Pd mobility make this a valuable contribution to the literature. It is appropriate for Chem Commun.
There is one relatively small change that should be made prior to publication. The manuscript claims that Pd is "more stable" in the bulk than on the surface; this is largely based on a 0.05 eV difference in the DFT slab calculations. While the data show that, indeed, the sub-surface Pd is 0.05 eV lower in energy, this difference remains within reasonable DFT errors and is therefore probably not significant. I can live with modifying these statements being modified to "slightly more stable".
The manuscript would also benefit from clarifying that the "slightly" is an important property of the system. It is only because the energy differences are small that the Pd-O bond energy is large enough to pull the Pd to the surface. Similarly, the Pd remains on the surface to do the catalysis (at least initially) after O removal BECAUSE there is only a weak driving force for it to migrate back into the bulk. The exchange is due to these small energy differences. If Pd was much more stable in the bulk, it would stay there during oxidation or it would likely migrate back quickly after O removal. Readers would benefit from having clear statements to this effect.
Response to reviewer #3: The statement made about Pd being more stable in the subsurface in pristine PdAu (211) is based on a difference of 0.27 eV (not 0.05 eV) which is significant. The