Peer review of: Single-atom Pt in intermetallics as an ultrastable and selective catalyst for propane dehydrogenat (2020)

<b>REVIEWER COMMENTS</B> 

Reviewer #1 (Remarks to the Author): 

In the present work, the authors reported an intermetallic PtGa catalyst, of which surface is selectively 
blocked by Pb deposition. The catalyst showed remarkably high selectivity and stability (coke resistance) 
during the PDH reaction. I believe that the study was carried out with very high scientific rigor. The 
structural characterization of catalysts, theorical simulations, and reaction results (including the 
comparison of many reported bimetallic catalysts) were all of high quality. I believe that the paper can 
be published in Nature Communications if the authors can address the following points. 

1. The authors compared several bimetallic catalysts in PDH. However, only the reactant conversion and 
propylene selectivity were compared. In my view point, most bimetallic and trimetallic catalysts suffer 
from dealloying due to the repeated redox cycles during a regeneration process. I strongly recommend 
the authors to additionally compare the recyclability of the prepared catalysts under a fixed 
regeneration condition. I believe that the present Pb-PdGa catalyst would be superior to other catalysts. 
2. The authors seemed to use carefully controlled regeneration conditions; oxidation under 5% O2/He at 
550°C followed by H2 reduction at 650°C. Is there specific reasons for choosing such a condition? What 
will happen if the coked catalyst is simply calcined in air (20% O2) at the reaction temperature (more 
practical conditions)? 
3. I am not sure whether the catalyst can be described as a “single-atom” catalyst. The Pb-modified PtGa 
catalyst does not have exposed Pt ensembles due to the site blocking by Ga and Pb. However, “single-
atom catalysts” generally mean the metal atoms or ions isolated within a “support” matrix. 


Reviewer #2 (Remarks to the Author): 

Review of Single-Atom Pt in Intermetallics: An Ultrastable and Selective Catalyst for Propane 
Dehydrogenation by Nakaya et al. 
The authors present a comprehensive study of a novel Pb-doped PtGa single Pt atom catalyst that 
performs exceptionally well for the selective dehydrogenation of propane to propylene. This PtGa-
Pb/SiO2 catalyst exhibits very high selectivity towards propylene and activity comparable to the more 
well-known Pt3Sn catalyst. However, more pertinently, PtGa-Pb/SiO2 shows no signs of deactivation 
due to coke formation after continuous runs of up to 96 hrs whereas other existing catalysts tend to 
deactivate to ~half their initial rate within a day or two precluding their practical use. The authors 
investigation concludes that Pb selectively blocks more reactive Pt3 surface sites but not the more 
selective single Pt sites that are thought to be responsible for the observed catalytic performance. 
Further DFT calculations reveal that unblocked single Pt sites exhibit comparable barriers for C-H 
activation in C3H8 and C3H7 though a very high barrier for further dehydrogenation that far exceeds 
that for propylene desorption. It is my opinion that the authors have presented an excellent 
contribution that is of the quality and novelty expected from an article in Nature Communications. 

Therefore I recommend that, subject to consideration of the minor comments below and some 
wordsmithing by the editorial team, this manuscript should be accepted for publication. 

Minor Comments: 
pg 3 line 6: “Owing to the endothermicity and limited equilibrium propane conversion, high 
temperatures are requires…” – limited equilibrium propane conversion does not make sense. 
pg 3 line 16: “For Pt-based catalysts, Pt–Pt ensembles are known to be active for deep C–H(C) activation 
and their hydrogenolysis.” – what is “deep” C-H activation? Is it C-H scission from lower valency C 
atoms? The term is used in several places and is not, as far as I’m aware, commonplace in the C-H 
activation literature. 
Figure 2d: A more appropriate label for the x-axis would be “Sputtering Cycle”. 
pg 6 line 20: “CO pulse chemisorption experiment supported the partial coverage of surface Pt, where Pt 
dispersion decreased from 9.9% to 5.9% upon the Pb modification to PtGa/SiO2” – this isn’t terribly 
clear though after checking Table SI1, it seems that as Pt/Pb decreases, the Pt % dispersion also 
decreases. The text should be revised to convey this. Also, the “Pt dispersion” should be defined. 
pg 8 line 19: “Although PtGa exhibited high conversion and selectivity at the initial stage (40% conv. 
99.1% sel. at 0.5 h), conversion gradually decreased below half within 50 h.” – half of it’s initial value, 
rather than absolutely half. 
pg 11 Figure 5 and discussion: units of eV are used in the figure and mostly kJ/mol in the text/Table 1. 
This should be made uniform. 
pg 11 line 15: “The displacement of the hydrogen atom to be eliminated becomes larger due to the 
absence of closely neighboring Pt, which significantly destabilizes the transition state.” The energy 
required for the displacement… 
General improvements and editing should be carried out to improve the readability.