CO2-H2O synergy enables stable tar model compound reforming over Fe–Cu biochar catalyst for clean hydrogen production

Efficient tar conversion and catalyst stability remain key challenges limiting the large-scale application of biomass gasification for clean hydrogen production. In this study, a low-cost and highly active Fe-Cu bimetallic biochar catalyst (SFBC-FeCu) was synthesized using sheep feces as the precursor via an integrated impregnation–pyrolysis method. The catalytic performance and deactivation resistance of the catalyst were systematically evaluated under N₂, 10 %CO₂, 10 %H₂O, and 10 %CO₂-5 %H₂O atmospheres. The results show that the 10 %CO₂-5 %H₂O co-feeding atmosphere effectively suppresses carbon deposition, alleviates metal particle sintering, prevents excessive oxidation-induced deactivation, and synergistically stabilizes oxygen-containing functional groups (OFGs) on the catalyst surface. By regulating the redox behavior of metal sites, incorporating lattice oxygen, and continuously generating oxygen vacancies, a favorable electron transfer cycle is established, ensuring the stable and efficient operation of the catalyst. After 90 min of reaction, the catalyst maintained a toluene conversion rate of 30.56 %. In contrast, under single-component atmospheres (N₂, 10 %CO₂, 10 %H₂O), the catalyst deactivated rapidly due to rapid carbon accumulation, metal site sintering or oxidation, unstable OFGs turnover, and hydrogen accumulation on active sites. These factors collectively result in a rapid decline in catalytic performance and stability. This study provides a feasible pathway and theoretical basis for developing highly stable biomass gasification systems.