Spinel-supported Fe-based catalysts for H2 production via catalytic methane decomposition: Experimental and theoretical studies

Catalytic methane decomposition (CMD) process has garnered significant attention for CO 2 -free hydrogen production. Fe catalyst has been widely investigated due to its low-cost and environmentally friendly features, but is prone to rapid deactivation due to elevated temperatures and coke deposition. To address these limitations, we synthesized a series of spinel-supported Fe catalysts with varying Fe/Mg/Al ratios via the sol–gel method. These catalysts were evaluated in a fixed-bed reactor, revealing that CMD performance depends significantly on Fe positioning within the spinel lattice in the as-prepared catalysts. Methane conversion was optimal and stable when Fe occupied octahedral sites, achieving 86.7 % CH 4 conversion and 92.9 % H 2 concentration in the outlet gas at 850 °C and 2 L g cat −1 h −1 . The mesoporous spinel structure enhances high-temperature stability and improves coke tolerance, which also contributed to additional layers of multi-walled carbon nanotubes. Density functional theory (DFT) calculations further identified the spinel-supported Fe catalysts as top performers. The energy barriers for the CMD process on Fe/MgAl 2 O 4 (1   1   1) and Fe/MgAl 2 O 4 (1   0   0) were lower than those on Fe(1   1   0). The difference charge density and Bader charge results of CH adsorption and dissociation on the structures, which was the rate-limiting step, demonstrated that the spinel support facilitated the efficient transportation and placement of electrons to the Fe cluster, thereby promoting C–H bond breaking. These findings offer novel insights into the design of cost-effective CMD catalysts with stable catalytic performance and high coke tolerance.