Peer review of: Surface oxygenation of multicomponent nanoparticles toward active and stable oxidation catalyst (2020)

Reviewer #1 (Remarks to the Author): 

It is a well-conducted piece of work reporting the dynamic valent state changes of Co and Ni in 
trimetallic PtCoNi NPs, and their consequences on oxidation reactions. The PtCoNi catalyst is indeed 
more active than Pt catalyst alone loaded on the same support. The characterizations are detailed and 
the origins of the increased activity is properly identified. I would recommend acceptance without 
revision should the paper is submitted to a specialized catalysis journal such as ACS Catal., the 
leading one in the area. 

Considering Nat. Commun. has a much broader audience, I have to see whether the paper has broad 
enough implications. Although the authors claim their catalyst represents a different design approach, 
and "may represent a paradigm shift in the design of self-supported catalysts", I am not able to be 
convinced. The report herein is a rebranding of what has already been known before. 

First of all, it is common knowledge that when PtM (M = 3d metal elements) is exposed to oxidative 
conditions, M on the surface will be oxidized, which then results in reorganization of the particle 
structure and electron distribution. The same applies to tertiary alloy particles such as PtCoNi studied 
in this paper. I do not see why this can be claimed as a design strategy for oxidation catalysts. 

Secondly, the method does not have tuning flexibility, since the oxidation state and structure of the 
PtNiCo NPs depend on the thermodynamics. That is, we can not control the NP to stay in the best 
possible electronic/geometric state for a certain reaction. Rather, that structure is determined by the 
reaction condition (one reaction condition, one structure). 

Another issue is the lack of control samples. It is a bit strange to see that the authors did not prepare 
and compare the structure and activity of PtNi and PtCo NPs. 



Reviewer #2 (Remarks to the Author): 

The authors present a very thorough study of propane total oxidation by ternary alloy nanoparticles. 
The breath of approaches applied to the problem and the number of samples studied is impressive. 
The authors conclude that the ternary alloy produces a more active catalyst by creating an active 
surface with mixed Ni and Co oxides decorated by Pt, as well as conclusions about the mechanism and 
instabilities in the kinetics. The conclusions are largely supported by the data, though some of the 
evidence in the main body of the paper is obscured by figures that are at best challenging to read. I 
have no doubts about the significance and novelty of the work, but considering its breath and the 
compromises in readability that the authors made to compress the paper to fit the page limits of a 
communication, I am not convinced this is the best venue for this paper. It would be much easier to 
follow and digest as a detailed long paper with all of the relevant figures in a single article, rather than 
needing to toggle to a supplement with 25 figures to understand what is going on. Below is a list of 
specific comments and questions the authors should address before publication. 

1)The Introduction co-mingles partial and total oxidation but the authors do not make it clear that this 
paper is focused on total oxidation and the arguments they make about metal and oxide supports are 
relevant to total oxidation. In contrast, partial oxidation catalysts are most often oxides of earlier 
transition metals, e.g. V and Mo. The suggestion is that the authors clearly state their focus on total 
oxidation. 

2) The ternary alloy phase diagram of Co-Ni-Pt is never mentioned but is extremely important. What 
is the miscibility range? Are there any ordered intermetallic phases? The description of the solid 
structure by a single fcc lattice constant suggests a solid solution, is this known to be the case over 
the composition range of interest? 

3) Line 95 – “further confirms the presence of the surface sites with Ni and Co atoms in the nearest 
neighbor of Pt atoms.” It’s not obvious how the figure tells us this, particularly since TEM sees through 
the entire particle. Since it is an important point the authors build on later on, it is important to 
explain how they came to this conclusion. 

4) Figure 1 and the discussion surrounding it on page 3 – the surface layer in Fig 1a is not obvious 
and in the accompanying Fig. S3a the labels on the image were illegible on my copy. The discussion of 
strain, I don’t understand the significance of the strain with respect to Pt, should be with respect to 
the bulk alloy with the composition of interest, and definitely need to indicate whether that strain is 
compressive or tensile. 

5) Also on page 3, concerning the EXAFS analysis, in the fcc structure how do you get >12 nearest 
neighbors (Ni-Ni = 13.2)? I don’t follow how the numbers lead to the suggestion of an ordered-layered 
structure. An ordered layered structure would not be consistent with a solid solution with an fcc 
structure. Review of information about what is known about the bulk ternary alloy would be helpful 
here. 

6) Catalyst aging – the aging conditions are very extreme compared to their operating conditions, did 
the authors see any changes in activity with time on stream? 

7) Figure 3 is so compressed that it is almost impossible to understand, it was only by looking in detail 
at the supplement that I was able to tell what was going on. The axis on the 3D plots are impossible 
to see, the color 3D IR spectra do not really show peaks that are easy to see when compared to the 
text, two of the three insets in the mass spec trace are impossible to see. The point about oscillations 
in the surface species does not come through at all, it is only in Figs. S19 and 21 that the reader can 
be convinced that this in fact occurs. 

8) Mass spec data – m/z = 44 corresponds to the parent ions of both CO2 and propane. The authors 
should try to correct the m/z = 44 trace for the propane contribution by analyzing the cracking 
pattern, e.g. the 44/29 ratio when only propane is leaked into the mass spectrometer. 

9) Page 7 Line 228 – “introducing lattice vacancy” where does this conclusion come from? 

10) Page 9 Line 309 – “regular-irregular oscillatory kinetics” This term is used in several places, I 
don’t know what it means. 

11) Also on page 9, first time experimental evidence of oscillatory kinetics. As a blanket statement this 
certainly can’t be true. Are they referring specifically to the Monte Carlo calculation referenced? This 
statement needs to be clarified. 




Reviewer #3 (Remarks to the Author): 

As the authors mentioned, oxidation reactions, total or partial oxidations, are widely used in the 
chemical industry and environmental governance, and the activation of gaseous oxygen is very 
important for these applications. The multi-component synergy of catalysts is one of the most 
important research topics in heterogeneous catalysis, and the interfacial interaction between different 
components is one of the key factors in determining the performance of catalysts. The present work 
reported an interesting phenomenon that the surface oxygenation of a multicomponent alloy of Pt with 
oxyphilic metals such as Ni and Co under catalytic reaction condition can generate multifunctional 
surface-active sites with substrate-active Pt center and surface oxygen-activating NiO/CoO sites. By 
using in-situ/operando time-resolved characterizations, the authors successfully show reasonable 
explanation and make fruitful discussion. Some insights in this phenomenon is expected to generate 
wide interest in this area. I recommend it to publish after a minor revision. Here are some specific 
comments for consideration during the revision. 
1.The authors called the surface oxygenation of Pt-alloyed multicomponent nanoparticles an Oxidation 
Catalysts. I cannot agree with it. In general, an oxidation catalyst means a non-metal oxidation 
catalyst. In the present work, the Pt-alloy is only partially oxidized. 
2.Since the active sites are very complicated, the calculation of TOF is questionable. Can the oxidation 
degree be added as a correction factor? The authors used changes of TOF over different samples to 
support their concussion that that the catalytic activity originates from the ternary compositions, 
which needs further discussion and more evidences. 
Is it possible that the surface oxidation of metal catalyst is common phenomenon? In the present 
work, what is the role of the alloy during self-oxidation. What happened for a single metal catalyst 
during the catalytic process? 
3.The authors highlighted that the self-activated catalysts are stable oxidation catalysts. However, no 
related data is given to show what will happen if the used catalysts are pretreated in reduction 
atmosphere for reuse. 
4.The discussions on reaction mechanism is a little confusing, especially on the Langmuir–Hinshelwood 
or Mars–van Krevelen pathway over different sites.