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

Abstract

Biomass-derived green hydrogen represents a promising route toward carbon-neutral energy. This study proposes an integrated catalytic pyrolysis strategy that achieves H₂ production and selective aromatic hydrocarbon formation over a Fe-Ni-CaO/C catalyst at 600 °C. The performance validation results demonstrated the superior efficacy of the Fe-Ni-CaO/C catalyst: the biomass-based hydrogen yield reached 345 mL g⁻¹ (Fe-CaO-Ni/0.2HC), which is 19.93% and 99.66% higher than those of the Fe-CaO/C and Fe/C catalysts (at the same reforming temperature of 600 °C and a 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 its 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 revealed that the 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.