Gas product behaviour using flower-like nickel-based MOF catalysts for sustainable hydrogen production from biomass

Abstract

Biomass pyrolysis offers a promising pathway for converting renewable feedstocks into hydrogen-rich syngas. However, the efficiency of this process depends heavily on the catalyst used. Nickel-based catalysts, while known for their catalytic activity and cost-effectiveness, often face challenges such as deactivation and agglomeration under pyrolysis conditions. To overcome these limitations, this study explores metal-organic frameworks (MOFs) as catalysts, with additional metal promoters to enhance Ni-based systems. Ni-MOF and Ce-Ni-MOF catalysts were synthesized and systematically evaluated, focusing on variables such as catalyst type, temperature, and catalyst-to-biomass ratio. Both catalysts exhibited highly textured, flower-like structures with loosely packed sheets, providing a large surface area for enhanced catalytic reactions. Ni-MOF increased hydrogen production by 96 % (13,785 mL/g, 53.0 vol%) within 10 min compared to non-catalytic conditions. Ce-Ni-MOF showed superior long-term performance, producing 2252 mL/g (44 vol%) of H₂ and achieving 66 % and 76 % higher hydrogen yields than Ni-MOF at 20 and 30 min, respectively. Structural analysis revealed that the catalysts’ flower-like morphology remained intact after pyrolysis, with increased porosity suggesting partial evolution of the MOF structure at high temperatures. Ni-MOF exhibited an increase in nickel loading from 39.8 wt% to 59.5 wt% post-pyrolysis, which further enhanced its catalytic activity. Ce-Ni-MOF displayed a narrower particle size distribution (6–11 nm) and improved stability, with nickel loading only slightly decreasing from 20.7 wt% to 18.4 wt%, maintaining uniformity over time. Both catalysts achieved optimal catalytic activity at a 1:1 catalyst-to-biomass ratio, although Ni-MOF experienced a 61 % reduction in H₂ production at a 1:4 ratio. Higher temperatures (800 °C) further enhanced hydrogen, CO, and CH₄ yields for both catalysts. These findings demonstrate the potential of MOF-based nickel catalysts for advancing renewable hydrogen production, with Ce-Ni-MOF offering enhanced stability and long-term catalytic efficiency under various conditions.