Defective zirconia promotes monometallic iron catalysts for higher alcohol synthesis

Abstract

Efforts spanning decades toward the implementation of direct synthesis of higher alcohols from syngas have been unfruitful. Progress is hindered by insufficient understanding derived from catalyst complexity, as the need for different functionalities usually requires combining various metals, promoters, and supports. We reveal that iron becomes a remarkable catalyst when promoted by zirconia. Iron with 10 mol % ZrO2 achieves a space-time yield of 250 mgHA h−1 gcat−1 and 30% selectivity to higher alcohols at their optimized conditions, superior to reported monometallic Fe catalysts and comparable to state-of-the-art multimetallic materials. This catalyst, with an outstanding balance between performance and simplicity, was examined via operando X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Oxygen vacancy formation and healing in amorphous ZrO2 clusters enhance H2 and CO activation and Fe5C2 formation in contact with Fe3O4. Activity-composition correlations suggest this Fe3O4-Fe5C2 interface as the active phase. Promoted monometallic iron emerges as a promising platform for future generations of catalysts.