Molten GaBi catalyst for low-carbon, cost-effective hydrogen via moderate- temperature methane pyrolysis

Methane pyrolysis is a promising method for CO 2 -free H 2 production. While conventional solid catalysts suffer from deactivation due to carbon product deposition, molten metal catalysts offer continuous operation for long-term stability by allowing carbon to float on the liquid surface. However, they typically require extreme temperatures above 900 °C to achieve a sufficient H 2 product yield, necessitating the development of catalysts with high activity at lower temperatures. Herein, we present a molten GaBi catalyst that is effective for methane pyrolysis at moderate temperatures of 500–800 °C. The Ga 0.11 Bi 0.89 alloy exhibited the lowest activation energy (67.2 kJ/mol) among reported molten catalysts and maintained stable hydrogen production for 158 h at 800 °C. Ab initio molecular dynamics calculations verified that the exceptional performance originates from the simultaneous suppression of Ga Ga aggregation (coordination number of 0.77) and enhancement of Ga mobility (diffusivity of 0.845 ± 0.012 cm 2 s −1 ). The 552 ton H 2 /day pyrolysis plant with the presented catalyst demonstrated superior economic and environmental feasibility compared to water electrolysis, achieving a net-negative environmental impact, a 80.7% reduction in total installed cost, and an 79.1% decrease in operating cost. The results provide critical insights that advance the design of efficient molten catalysts for methane pyrolysis. • Molten GaBi catalyst enables CO 2 -free H 2 production at 500–800 °C. • The Ga 0.11 Bi 0.89 alloy exhibited an activation energy of 67.2 kJ/mol. • Stable operation for 158 h was observed at 800 °C in a bubble column reactor. • Simulations revealed the suppression of Ga Ga aggregation and enhanced Ga mobility. • 552 ton H 2 /day plant achieved superior economic and environmental feasibility.