Biomass pyrolysis with Fe-Ni-CaO char-based catalyst for efficient green hydrogen generation and bio-oil upgrading via coupled C-H/O-H activation

Abstract

Biomass-derived green hydrogen is a promising route toward carbon-neutral energy. This work presents an integrated catalytic pyrolysis strategy that realizes H2 generation and selective aromatic production using a Fe-Ni-CaO/C catalyst under 600 ℃. Performance validation results demonstrated the superior efficacy of the Fe-Ni-CaO/C catalyst: the biomass-based hydrogen yield reached 345 mL/g (Fe-CaO-Ni/0.2HC), which is 19.93% and 99.66% higher than that of the Fe-CaO/C and Fe/C catalysts (the same reforming temperature of 600 ℃ and 1:2 catalyst-to-feedstock mass ratio), respectively, marking a significant breakthrough in low-energy hydrogen production from biomass. Additionally, the catalyst achieved 100% conversion of heavy oil fractions in pyrolysis oil and 100% selectivity toward high-value benzene and toluene. Systematic parameter optimization shows that the tri-metallic synergistic system outperforms single-metal and dual-metal counterparts in catalytic activity; a 2:1 feedstock-to-catalyst mass ratio achieved a balance between raw material conversion and target product selectivity. Characterization and DFT analysis reveal that Fe-Ni redox coupling facilitates C–H bond activation and continuous H2 evolution, while controlled carbon-chain scission governs aromatic upgrading. This study establishes a mechanistic and scalable framework for low-energy catalytic biomass valorization, advancing sustainable hydrogen and bio-aromatic production.