Abstract The review provides a short summary of the production of turquoise hydrogen using catalytic methane pyrolysis, focusing on transition metal (Fe, Ni, Co) and carbon-based catalysts. Methane pyrolysis enables the production of CO 2 -free hydrogen, with solid carbon serving as a valuable by-product. Fe, Ni, and Co catalysts are highlighted due to their strong C–H activation capacity, high activity, and economic feasibility. In turn, carbon-based catalysts offer high thermal stability and resistance to coking, providing a longer catalyst lifetime. Other materials, such as noble metals or complex oxides, are less considered due to the cost, limited scalability, or lower selectivity in solid carbon formation. Focusing on combined cocatalysts and carbon systems provides a balance between catalytic performance, durability, and economic viability, which is the most practical direction for promoting sustainable turquoise hydrogen production.
Sika et al. (Mon,) studied this question.