Enhanced activity and stability in microwave steam reforming of tar with TiO2-coated zeolitic imidazole framework-67 derived Co/C

Microwave steam reforming using carbon-based catalyst presents a promising solution for tar elimination in biomass gasification, crucial for renewable syngas production toward heating, electricity, and value-added chemicals. However, activated-steam-induced catalyst deactivation remains challenging. Herein, a ZIF-67-derived core-shell Co/C-TiO 2 catalyst was engineered via tailored TiO 2 hydrophilicity and structural protection. Catalytic performance exhibited a volcano-type trend versus TiO 2 shell thickness. The optimal catalyst (Co/C-T2) achieves a 96.62 % toluene conversion rate and a 72.17 % carbon conversion rate at 550 °C, sustaining >87.61 % efficiency over 6 h. Structural characterizations revealed the core-shell architecture transformed carbon-supported Co(111) structure into anatase TiO 2 (101)-stabilized Co 3 O 4 (311) configuration, significantly enhancing surface basicity and oxygen species density. DFT-based molecular dynamics simulations further elucidated the mechanism by demonstrating reduced adsorption and dissociation energy barriers for H 2 O molecules, which facilitate steam activation in the reforming process. However, excessive TiO 2 coating induces diffusion limitations at the reactant/metal active site interface, coupled with coking-induced pore occlusion, consequently triggering significant deterioration in catalytic activity and stability. This work establishes a facile modification paradigm for developing microwave-responsive carbon catalysts while providing fundamental insights into the structure-activity relationships of core-shell systems in heterogeneous catalysis. These findings offer practical guidance for designing advanced catalysts in sustainable energy conversion applications.