Peer review of: Atomically dispersed cobalt catalyst anchored on nitrogen-doped carbon nanosheets for lithium-o (2020)

Reviewers' comments: 

Reviewer #1 (Remarks to the Author): 

This manuscript reported a catalyst Co-SAs/N-C synthesized by a green gas-migration-trapping 
procedure which can act as bifunctional catalyst for Li-O2 batteries. However, it has been reported 
that catalyst is not effective for oxygen evolution reaction but mainly CO2 evolution (JACS, 2011, 133, 
18038-41). To defend their work, the authors should provide evidence if their catalyst is doing O2 
evolution or CO2 evolution. Otherwise it could be just side reactions. 

1.In Figure 3g and 3h, cycling at 400 mA g-1 under a capacity of 1000 mAh g-1 is less than 1/10 of 
the total capacity (16000 mAh g-1 (Supplementary Figure 14a)). How would the cycle life change 
when cycling at a more reasonable capacity say 70-80% of the total capacity? 
2. More characterization of the discharge product of Li2O2 such as Roman is required to confirm the 
small particle/amorphous Li2O2 which is not easy detected by XRD. 
3. In Supplementary Figure 14 (a-c), please label the cathode material. 



Reviewer #2 (Remarks to the Author): 

In this manuscript, Wang et al. prepared an atomic cobalt catalyst supported on N doped carbon, 
which shows a superior capacity and an excellent stability. The results are interesting, and some 
points are need to be clared before it is considered to be published. 

(1) The XPS peak fitting is failed in Fig 2a, where the same N species shows a large difference in 
FWHM, especially pyrrolic N. 
(2) In line 126, page 4, it makes a confusion by the description “the Co K edge XANES in R and k 
space”. And the conclusion is less rigorous with the square-planar Co-N4 configuration from the Co K 
edge EXAFS spectra. One of standard references should be put into Table S2 and all of error bars for 
each parameter should be provided. 
(3) In Fig. 3a, the authors should give more discussion for the CV curves. What’s the meaning of the 
peak around 3.5 V? 
(4) After the discharge, the SEM is more suitable to check the uniform of the Co-SAs/N-C in a large 
scale. 
(5) How about the electronic state of the Co 2p for Co-SAs/N-C after the long-time cycles, in 
comparison with the pristine one? 
(6) Some previous works have been published, such as Na-S batteries (Nat. Commun., 2018, 9, 4082), 
Li-metal batteries (Adv. Energy Mater., 2019, 9, 1804019) and Li-S batteries (J. Am. Chem. Soc., 
2019, 141, 3977-3985; Adv. Mater., 2019, 31, 1903955). It should be summarized and discussed in 
the introduction section. 
(7) The details of DFT calculation is missing. Most important, the descrption of the model used in 
current study is not described. Therefore, the validity and relaibility of current calculation can not be 
evaluated. For example, in Figure 30 in supporting infomration, there is a huge deformation of 
graphene, probably because authors used a bad model. Meanwhile, the huge adsorption energy of 
LiO2 on Co-N is strange, which means the active site of Co-N will be "poisioned" due to the adsorption 
of LiO2. Again, it is not professional to describe the adsorption energy with four number after decimal 
point. Does the calculated accuracy reach the level of meV?