Catalytic mechanism of Ca doped Ni–Fe during biomass steam gasification for hydrogen-rich gas: Experiments and density functional theory calculations

Biomass catalytic reforming for hydrogen or syngas production is one of the important research directions. In this paper, the Ni–Fe–Ca catalyst was selected as the research object. The aim was to clarify whether Ca doping has a synergistic or antagonistic effect on the Ni–Fe catalyst during the biomass steam catalytic gasification process and to elucidate the mechanisms of both. The fixed-bed experiment results showed that Ca doping significantly increased the syngas yield. When Ca completely replaced Fe, the hydrogen concentration reached 65 vol%. The presence of Fe could slow down the increase in grain size in the material, thus delaying the sintering of the material. Density functional theory (DFT) calculations revealed that the Fe-modified surface had a stronger affinity for CO and the Fe atoms had a relatively strong interaction with the (CaO)₄ cluster. This inhibited the migration and agglomeration of the cluster, which further verified the fixed - bed experiment results. This study provided valuable insights into the technical routes for biomass catalytic reforming to produce hydrogen or syngas and the design of Ni–Fe–Ca catalysts.