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

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 Fe1Zn0.1K0.1 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 Fe1Zn0.1K0.1 reaches 0.40 g·gcat–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, Fe1Zn0.1K0.1 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.