Highly Efficient CO2 Hydrogenation to Linear α-Olefins on FeZnK Catalysts with Balanced Zn–O–Fe Interfaces and Fe5C2 Species

Abstract

C₄₊ linear α-olefins (LAOs) synthesis from direct CO₂ hydrogenation is a promising strategy to realize the fixation of CO₂ to high-value chemical products. However, identifying active catalysts with satisfactory activity and selectivity is quite difficult nowadays. Herein, we fabricate a series of iron–zinc–potassium (FeZnK) catalysts via a citric acid-mediated combustion method that can both actively and selectively synthesize LAOs from CO₂ hydrogenation. The Fe₁Zn_0.1K_0.1 catalyst with balanced Zn–O–Fe interfaces and active Fe₅C₂ species provides an LAOs selectivity of 44.7% at a high CO₂ conversion of 43.3% in CO₂ hydrogenation. Notably, the space–time yield of LAOs over Fe₁Zn_0.1K_0.1 reaches 0.40 g·g_cat^–1·h^–1, surpassing the performance of current state-of-the-art Fe-based catalysts. The reaction results and multiple characterizations reveal that the introduction of an appropriate amount of Zn composition can not only enhance the CO₂ adsorption ability by forming Zn–O–Fe interfaces but also improve the LAOs selectivity by promoting the formation of active Fe₅C₂ species. Interestingly, active Fe₅C₂ species tend to form in the bulk phase of the FeZnK catalysts, which are more closely correlated with catalytic activity. In situ/ex situ characterizations combined with H₂/D₂ exchange and CO pulse hydrogenation probe experiments elucidate the structure–activity relationship and reaction mechanism. Furthermore, Fe₁Zn_0.1K_0.1 shows a 160 h long-time on-stream stability, indicating its strong potential as an industrial catalyst for direct CO₂ conversion to high-value LAOs.