Surface functionalization and molecular mechanisms of KOH- modified activated carbon catalysts in methane decomposition for hydrogen production

Catalytic decomposition of methane (CMD) is a promising approach for CO₂-free hydrogen production, accompanied by solid carbon formation. However, the rapid deactivation of carbon-based catalysts due to carbon deposition and pore blockage remains a major challenge. In this work, a series of KOH-modified activated carbons were synthesized and evaluated for CMD at 950 °C. Catalyst performance and structural evolution were systematically investigated through SEM, XRD, BET, XPS, Raman and molecular simulations. KOH treatment significantly enhanced catalytic activity by introducing surface defects and oxygen-containing functional groups. The catalyst modified with 4 % KOH showed the best performance, achieving a hydrogen yield 50.94 % higher than that of unmodified carbon and maintaining a final methane conversion of 32.4 %. Potassium removal led to reduced activity, confirming its role in stabilizing active sites. Post-reaction characterizations revealed that deactivation is primarily caused by graphitization and pore blockage. Simulations based on molecular dynamics and density functional theory demonstrated that polar groups, especially carbonyl and carboxyl, enhance methane adsorption through strong electrostatic interactions and increased adsorption heat. These insights contribute to the rational design of efficient, stable, and metal-free carbon-based catalysts for clean hydrogen production.