One-Step Synthesis AlCo₂O₄ and Derived “Al” to Double Optimise the Thermal Decomposition Kinetics and Enthalpy of Ammonium Perchlorate

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Dear Authors,

Thank you for submitting your manuscript, “One-step synthesis AlCo2O4 and derived “Al” to double optimize the thermal decomposition kinetics and enthalpy of ammonium perchlorate.” The Reviewer finds the work interesting and relevant to the field of energetic materials. The following suggestions are provided for improvement:

 

1. While the dual-optimization concept is understood, please ensure the Introduction and Conclusion sections explicitly state that the key novelty is the one-step synthesis of a composite catalyst (AlCo2O4 + in situ Al) via φ-controlled solution combustion, designed to tackle both AP decomposition kinetics and contribute metallic fuel enthalpy, distinguishing it from studies focusing solely on pure AlCo2O4 or other catalyst types.
2. Lines 217-227. The results indicate that the best-performing catalyst (φ = 0.5) has the smallest surface area and the largest pore size among the synthesized samples. This seems counterintuitive, as higher surface area usually implies more active sites. Please include a more explicit discussion that addresses why, in this specific system, the sample performs best despite these structural parameters. 
3. The text mentions derived "Al" nanoparticles based on XPS (Fig. 6a-c, Table 4) and discusses their role. However, clear visualization of these distinct metallic Al nanoparticles (beyond the host oxide structure) is not immediately apparent in the provided TEM images (Fig. 2d). Could you comment on this or point to specific features, highlighting them in the figure?
4. Some sentences are long and could be broken down for clarity. A final proofread focusing on sentence structure, conciseness, and grammatical flow is recommended.
5. The reference list includes several papers involving the corresponding authors (e.g., [29, 37, 46, 52, 59, 60, 64]). Please briefly review these self-citations to ensure each one is essential for providing necessary context or methodological background and that reliance on self-citation is not excessive.

Comments on the Quality of English Language

English is functional for conveying the research, but it lacks the clarity and polish of high-quality scientific writing, primarily due to complex sentence structures. 

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript presents a study on the synthesis of AlCo₂O₄ and derived metallic aluminum nanoparticles via a one-step solution combustion method, with varying oxidizer-fuel ratios. The materials are evaluated for their catalytic effect on the thermal decomposition of ammonium perchlorate. The study demonstrates that AlCo₂O₄ prepared at φ = 0.5 significantly reduces the high-temperature decomposition temperature of AP by 188.08°C, lowers the activation energy by 84.47 kJ/mol, and enhances the decomposition heat. 

In order to enhance the manuscript, there are some areas which require improvement.

Abstract:
- The abstract is informative but contains minor inaccuracies. For example, it states that AlCo₂O₄-0.5 has a “more excellent catalytic effect” than other samples, but Table 2 shows AlCo₂O₄-2 has a higher decomposition heat increase (1555.14 J/g vs. 1088.04 J/g for AlCo₂O₄-0.5). This discrepancy should be clarified. Additionally, the abstract could better emphasize the dual role of Al.

Methodology:
- The synthesis section (2.2) is clear, but the rationale for choosing φ values (0.5, 1, 2) is not explained. The authors should justify why these specific ratios were selected and whether other ratios were tested.
- The study optimizes the AlCo₂O₄-0.5 dosage (2–10 wt%) and identifies 7 wt% as optimal, but the reason for the increase in HTD temperature at 10 wt% is not discussed. This could be due to catalyst overloading or agglomeration, and a brief explanation would strengthen the analysis.
- The use of both Kissinger and Friedman methods is interesting, but the Friedman results (Table 3) show significant variation in activation energy (102.01–252.68 kJ/mol). The authors should discuss why Ea fluctuates and how it relates to the decomposition stages (LTD vs. HTD).

Results and discussion:
- The results are well-presented, but some sections lack depth in interpretation. For instance, the discussion of why AlCo₂O₄-0.5 outperforms AlCo₂O₄-1 and AlCo₂O₄-2 focuses on Co³⁺ and Ov content but does not fully address the role of pore size or crystallinity differences.
- The BET results (Table 1) show that AlCo₂O₄-0.5 has the smallest specific surface area (121.473 m²/g) yet the best catalytic performance. The authors conclude that surface area is not the primary factor, but they do not explore alternative factors (e.g., active site density, Al content) in depth. A more detailed discussion would strengthen this point.
- XPS Analysis: The reported Al/Al³⁺ ratio for AlCo₂O₄-0.5 (0.27) in Table 4 does not match the text’s claim of 0.76 (Page 10). This inconsistency must be resolved. Additionally, the role of oxygen vacancies in catalysis could be quantified (e.g., by comparing Ov content across samples).

Conclusion:
- Authors should expand the conclusion to include future research directions.

- Authors could include additional data (e.g., TG-MS spectra for all samples, detailed kinetic calculations) to support the main text.

Author Response

Please see the attachment

Author Response File: Author Response.pdf