Engineering the microenvironment in Ba-doped Fe catalyst with alkali metal promoters for enhanced CO2 hydrogenation to α-olefins

The catalytic conversion of CO₂ into olefins holds significant promise for carbon neutrality. However, achieving precise control over target olefin selectivity requires the development of an efficient catalyst. Herein, we explore the impact of alkali metal (AM) promoters on the reactive microenvironment of Ba-doped Fe catalyst for enhanced CO₂ hydrogenation to α-olefins. The results revealed that Na/BaFe and K/BaFe catalysts exhibited the highest efficiency among the studied catalysts, with enhanced reducibility, surface reactivity, and olefin selectivity due to the increased FeC_x sites induced by the AM promoters. Notably, Na/BaFe, with more surface FeC_x coverage, facilitates the production of C_2-4-rich α-olefins, while K/BaFe surfaces are more conducive to generating C₅₊-rich α-olefins. Li/BaFe exhibited the lowest α-olefin selectivity. The highest α-olefin selectivity (68.8 %) was achieved with Na/BaFe, making it an efficient Fe-based catalyst for CO₂ hydrogenation to α-olefins. Compared to BaFe, in situ DRIFTS confirmed that Na/BaFe facilitated the formation and subsequent hydrogenation of CO species, promoting chain growth and reducing excessive CH₄ and CO production, attributed to facile carburization. The study provides valuable insights for optimizing Fe-based catalysts for CO₂ hydrogenation.