Adsorption of H2 on Penta-Octa-Penta Graphene: Grand Canonical Monte Carlo Study
Round 1
Reviewer 1 Report
In this manuscript, the authors implemented the Grand-Canonical Monte-Carlo (GCMC) approach with different potential parameters to calculate the adsorption of H2 on graphene and POP-graphene at two different temperatures (298K and 77K). Their results show a moderately better performance of the POP-graphene at 77K. Several explanations and clarifications are needed in a revised manuscript.
1. Figure 3, the H2 uptake shows an almost linear relationship with the pressure at 298K while a different trend is observed at low temperature (77K). This needs to be discussed in the paper.
2. Figure 4, the excess H2 uptake slightly decreases at larger slit width at 298 K (top panel), while it shows an increasing trend at 77K (bottom panel). What is the possible explanation?
3. Line 125, the authors said “exhibits 1 (for 10 Å) and 3 peaks (for 30 Å)”. Based on figure 6, it looks like 2 strong peaks (for 10 Å), 4 peaks (2 strong, 2 weak for 15 Å) and 4 peaks (2 strong, 2 weak for 30 Å). How did the authors count these peaks?
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
By grand canonical Monte-Carlo simulations, the authors estimate the hydrogen adsorption capacity of Penta-Octa-Penta (POP) graphene a new type of carbon bidimensional crystal. The adsorbent material studied by simulation is an arrangement of equidistant parallel POP graphene planes and, so, has a slit-pore geometry. The adsorption estimate is performed by using different pair potentials for modelling
the interaction between hydrogen molecules and that between hydrogen molecules and carbon atoms. The considered pair potentials are either potential already used in the literature or recently derived by fitting ab-initio calculations.The simulation results show that, in spite of
noticeable quantitive differences between the pair potentials, the computed gravimetric and excess computed gravimetric capacities and isosteric heats of adsorption of POP graphene, for all interaction models, are very close.
These results reinforce the assertion that, for any adsorbent materials having an adsorbent surface similar to graphene, the H2 excess adsorption capacity is weak at room temperature and pressure below 100 bars and, in the same domain of pressures, only significant at temperature below 100 K. Interesting between graphene and POP graphene is the remarkable variation of localisation of H2 molecules in the first adsorbed layer.
I believe that this work is a valuable contribution to estimate the adsorption properties of the new material: the POP graphene, and shows that physically acceptable modelling of the interactions between H2 and carbon adsorbents give coherent estimates.
I believe that this article deserves to be published in Carbon.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
Present manuscript describes investigation on H2 adsorption on POP-graphene.
The article is well-written, detailed and logically structured. The article could be interesting for the general auditory of Journal of Carbon Research.
However, there are some concerns that need to be addressed:
- The difference in H2 adsorption properties between POP-graphene and hexagonal graphene (even at 77K less than 1%). Authors should emphasize why they think that application POP-graphene in H2 adsorption is important, because synthesis of POP-graphene is more complicated.
- How defects in both hexagonal graphene and POP-graphene will affect H2 adsorption?
- Do two types carbon atoms in POP-graphene have different acidity?
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
