Synergistic catalytic biomass-H2O gasification for H2 production and biochar etching mechanism: Experimental and DFT studies

Biomass-H₂O gasification facilitated by multi-metal synergistic catalysis for H₂ production. Oxygen transfer, carbon dissolution, lateral/vertical etching mechanism, and hydrogen production capacity of biomass self-contained K and added Ni catalytic gasification were studied through biomass loaded with K and Ni pyrolysis, biochar gasification experiments, and DFT calculations. The H₂ yield from KNi catalytic gasification was 67.09 mmol/g (increased by 13.51%). Driven by *OH, K migrates and transforms from the inside of the carbon matrix to form active sites (C_K), increasing carbon defects (40–50%) and reactivity. The vertical etching ability of Ni on biochar is enhanced from outside to inside (forming NiC and C_K to reduce carbon dissolution energy barrier) and the gasification reaction rate is increased. The competition between the strong attraction of Ni on OH and the van der Waals force of K on OH leads to a 7.7% increase in the energy barrier of the rate-determining step (H transfer). The work enhances the understanding of the multi-metal catalytic gasification of rich H₂ and provides a foundation for developing catalytic gasification technology.