The global transition to low-carbon energy systems necessitates sustainable alternatives to conventional fossil fuel-based technologies. Hydrogen is a promising clean energy carrier; however, its current production methods, such as steam methane reforming, are associated with high greenhouse gas emissions [1]. Methane pyrolysis offers a low-emission alternative by thermally decomposing methane into hydrogen and solid carbon, without CO₂ as a by-product [2]. The use of catalysts in this process significantly lowers the required temperature for methane cracking, thereby improving the overall energy efficiency of the process. Liquid catalysts offer advantages over solid ones, as they avoid deactivation caused by carbon deposition [3]. The solid carbon formed during the reaction floats on top of the molten bath and can be easily removed. To date, research on liquid metal reactors has primarily focused on liquid non-ferrous alloys, such as nickel, copper, bismuth, and tin [4–6].

This study investigates the catalytic performance of iron–silicon–manganese alloys as liquid metal catalysts for the methane pyrolysis. The experiments were conducted in a lab-scale reactor and the main performance indicators evaluated were methane conversion and hydrogen yield under varying alloy compositions.

Results demonstrate that increasing the silicon content in the alloy significantly enhances methane conversion and hydrogen output. In contrast, the role of manganese remains inconclusive based on the available data. Post-reaction SEM analysis of the carbon product revealed contamination due to metal discharge from the catalyst, resulting in impurities that may limit direct carbon utilisation.

These findings highlight both the potential and challenges of using molten iron alloys in catalytic methane pyrolysis. Further research is required to optimise catalyst composition, minimise carbon contamination, and assess the scalability of this approach for industrial hydrogen production with integrated carbon management.

Hydrogen is increasingly recognized as a critical vector in decarbonizing industrial energy systems. Its utilization as a fuel and reducing agent in sectors such as metallurgy and chemical processing has the potential to reduce greenhouse gas emissions and enhance energy system resilience significantly [1]. However, conventional hydrogen production, e.g., via steam methane reforming, is associated with substantial CO₂ emissions, necessitating the development of more ecological alternatives [1]–[4].

Methane pyrolysis in metallic melts has emerged as a promising route for CO₂-free hydrogen generation [3], [5]. In this process, methane is decomposed in an oxygen-free atmosphere in the presence of a liquid-metal catalyst to form solid carbon and gaseous hydrogen [3], [5]. The process operates at a comparable specific energy demand to steam methane reforming but circumvents direct carbon dioxide formation [3], [4]. The pyrolytic carbon produced constitutes a potentially valuable co-product whose physicochemical properties strongly influence its marketability and the overall economic viability of the process [4].

This study focuses on the specific energy demand of methane pyrolysis in molten metals, combining theoretical analysis with experimental findings. The influence of the nitrogen and methane inputs on energy consumption is investigated in laboratory scale-ups. The results enable a comparison with conventional hydrogen production routes and provide critical insights for designing integrated methane pyrolysis systems aimed at sustainable hydrogen and carbon co-production.