Monodisperse Hierarchical N-Doped Carbon Microspheres with Uniform Pores as a Cathode Host for Advanced K–Se Batteries

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Review

batteries-3497913

The manuscript submitted by Seung-Keun Park et al. concerns the synthesis, characterization and electrochemical performance of monodisperse hierarchical N-doped carbon microspheres (NCHS) as cathode materials in K-Se batteries. The chosen topic is sound and very useful. Material is well characterized using various methods (SEM, TEM, BET, BJH, TGA and Raman) with only XPS potentially lacking to complete the picture of its structure. Electrochemical performance of prepared catalyst is good. Manuscript is overall very well written and results are clearly presented. The manuscript is acceptable for publication after addressing the comments below.

Comments

1. Lines 177-180 and lines 182-185 state the exact same thing twice in a row.
2. XPS measurements are highly recommended. Some of the conclusions reached by authors such as: “These findings confirm the complete removal of MoOx, resulting in a porous amorphous carbon matrix”, “Notably, no residual Se powder was observed on the outer surface of the carbon after Se loading, indicating the successful encapsulation of Se within the NCHS structure”, “This structure enabled high surface Se loading, with no unincorporated or overgrown Se observed, and showed that more Se was loaded on the surface than within the internal pores” and especially in conclusion “N doping, naturally introduced during the synthesis process, strengthened the chemical bonding between Se and the carbon host” while seemingly sound and correct, can only be definitively confirmed by XPS analysis of the surface chemistry and composition.
3. References are not cited with uniform style.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

In this work, Se-loaded N-doped carbon spheres (Se@NCHS) with a uniform flower-like hierarchical architecture were developed as a cathode material for K-Se batteries.  Specially, the flower-like microstructure, mitigated Se aggregation and facilitated uniform distribution  within the pores, enhancing Se utilization. Impressively，Se-loaded NCHS (Se@NCHS) exhibited  a high discharge capacity of 199.4 mA h g-1 at 0.5 C after 500 cycles with 70.4% capacity retention. This work is well organized and can be published with minor revisions.

Here are my comments regarding this work:

1,  Compared with the previous reports, what is the advantage of this work?  Carbon microspheres applied as cathode host is a common strategy, the author had better consider how to highlight the merit of the proposed Se@NCHS strategy. 

2,  In Figure 6b, the author mentioned "At current densities of 0.1, 0.2, 0.5, 1.0, 1.5, 2.0, 2.5, and  3.0 C, the discharge capacities of the Se@NCHS electrode were 384, 355, 318, 271, 252, 225,  202, 182, 192, 210, 238, and 264 mA h g-1, respectively" Please check the data again, as it is clear that the discharge capacity at 3.0C is lower than 200 mA h g-1.  And also check the data between line 332 and 344, and keep the comments accurate.  Additionally, check the Abstract, as the author mentioned "achieved 282 mA h g-1 at 3.0 C"

3, Is the pore size of the carbon microsphere optimized? A discussion regarding this had better be provided. 

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Accept