The stabilisation of Pt–Fe dual-metal single atoms (SAs) anchored in ZIF-derived N-doped carbon under high-temperature pyrolysis is thoroughly examined in this work, which is monitored using in situ high-resolution HAADF-STEM. In contrast to the instability of single Fe systems, the discovery offers a clear mechanistic understanding of how Pt–Fe hetero-pair interactions inhibit Fe aggregation and evaporation.

The design of dual-atom catalysts (DACs) benefits greatly from the fundamental knowledge provided by the combination of in situ TEM, ex situ structural characterisation, and systematic precursor concentration change. Both the methodology and the technical quality of the work are excellent.

However, the submission would benefit from (i) a clearer explanation of its originality beyond Pt–Fe/ZIF systems, (ii) catalytic relevance or at least predictive of performance implications, (iii) a quantitative analysis of hetero-pair distribution, and (iv) a clearer assessment of electron beam effects in in situ experiments in order to fully meet Materials Horizons’ emphasis on conceptual advance and broad impact. Kindly consider the following improvements:
1. The study focuses exclusively on structural evolution, but no catalytic performance data is shown. Even if performance testing is outside scope, a quick proof-of-concept catalytic evaluation or discussion of prospective activity/selectivity trends based on the observed structures will improve the effect for Materials Horizons, which seeks wide materials relevance.
2. Although electron beam-induced effects (such as Fe₃C production) are acknowledged in the text, the extent to which the beam affects the observed structural evolution in comparison to pure thermal effects is not adequately quantified or discussed.
3. Given the high cost of Pt, the authors might talk about whether it is possible to substitute other noble or non-noble metals for Pt while maintaining the effects of hetero-pair stabilization.
4. The STEM analysis does not include a statistical distribution analysis (e.g., percentage of atoms existing as hetero-couples vs. isolated SAs), but it does qualitatively identify Pt–Fe pairs. This would assist in measuring the degree of stabilization.
5. The HPF-ZIF results are intriguing, but further explanation—possibly with references to DFT literature—is required for the mechanistic basis of the preferential Pt-doped α-Fe production (instead of carbides or distinct phases).
6. Improve visibility and more clearly annotate important elements in certain HAADF-STEM images due to their low contrast. Scale bars should be more obvious.
7. Terminology used should be uniform. In the Introduction, the terms "SAs," "hetero-pairs," "NCs," and "NPs" should be defined precisely and used consistently.
8. Include citations from operando DAC investigations, as some DAC-related references are quite recent yet restricted to particular systems.