Atomistic insights into catalytic role of platinum-graphene nanostructures in decomposition of high-energy-density fuels

초록

To advance the cooling performance critical for hypersonic vehicles, high-energy-density fuels have emerged as promising candidates, with platinum-graphene (Pt@FGS) nanocatalysts demonstrating significant potential for enhancing their regenerative cooling efficiency. However, the underlying catalytic mechanisms of these nanocatalysts, particularly their influence on reaction pathways and carbonization processes, remain insufficiently understood. This study employs a ReaxFF-based hybrid simulation approach to investigate the effects of Pt@FGS nanocatalysts on the decomposition of exo-tetrahydrodicyclopentadiene (exo-THDCPD) across a broad temperature range (900-2000 K). The Pt@FGS nanocatalysts were modeled as a partially oxidized graphene structure with six platinum atoms anchored at defect sites. ReaxFF molecular dynamics (MD) simulations were performed to capture real-time pyrolysis pathways and nanocatalyst-fuel interactions at the atomic scale. To extend the timescale and observe low-temperature pyrolysis relevant to experimental conditions, the collective variabledriven hyperdynamics (CVHD) method was employed. Nudged elastic band (NEB) calculations quantified key bond dissociation energy barriers, providing insight into catalytic dehydrogenation mechanisms. The MD results revealed that Pt@FGS nanocatalysts reduce the activation energy by approximately 33 % compared to neat fuel, significantly enhancing fuel conversion rates by up to a factor of four through catalytic dehydrogenation. Heat sink capacity improvements were observed at lower temperature ranges, attributed to nanocatalyst-promoted dehydrogenation, as confirmed by NEB analysis. The CVHD approach enabled pyrolysis simulations under experimentally relevant conditions, yielding activation energies and product distributions consistent with those obtained from high-temperature MD simulations. Interestingly, additional MD simulations demonstrated Pt@FGS nanocatalysts can delay carbonization onset effectively suppressing the formation of carbon deposits. By combining MD, CVHD, and NEB analyses, we elucidated the reaction mechanisms of exo-THDCPD decomposition over Pt@FGS nanocatalysts. The results demonstrate at the atomistic scale that Pt suppresses coke formation by interacting with intermediates and hindering aromatic ring closure, providing insights into the design of fueldispersible catalysts for regenerative fuel cooling.

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