Lattice oxygen-mediated bifunctional Fe/γ-Al₂O₃ for cyclic biomass gasification coupled with CO₂ splitting

With the extensive utilization of biomass energy, the efficient use of byproduct CO₂ can promote negative carbon emissions in biomass utilization processes, serving as an important approach for carbon removal. This study develops an innovative strategy for synergistic CO₂ utilization through integrated biomass gasification and CO₂ reduction using bifunctional Fe-based oxygen carriers. Nano zero-valent iron (nZVI) and Fe/γ-Al₂O₃ composites were engineered to serve as high-efficiency reductants for CO₂-to-CO conversion at elevated temperatures, and as oxidants providing lattice oxygen for generating high-quality syngas from poplar wood feedstock. The physicochemical properties of the oxygen carriers were characterized using XRD, BET, SEM and TEM. The characterization results revealed that Fe species were homogeneously dispersed on the γ-Al₂O₃ support with minimal aggregation. Comparative redox performance tests demonstrated the superior activity of Fe/γ-Al₂O₃ oxygen carriers over pure nZVI. Redox performance evaluations of oxygen carriers with varying Fe loadings (60-100 wt%) identified 80 wt% Fe/γ-Al₂O₃ as the optimal formulation, achieving a syngas yield of 13.42 mmol/g_biomass at 900 °C. while simultaneously enabling efficient CO₂ conversion with a production rate of 51.15 mmol CO at 900 °C. The revealed lattice oxygen transfer mechanism establishes a sustainable pathway for concurrent biomass valorization and carbon utilization.