Unsaturated ZrO_x Sites Boost C–C Coupling for Selective CO₂ Hydrogenation to Olefins

Abstract

Direct hydrogenation of CO₂ to synthetic fuels and olefins using renewable hydrogen remains challenging owing to the scarcity of low-cost, active, and highly selective catalysts. Current catalytic systems often exhibit either excessive CO selectivity or generate substantial alkanes to cause a low olefin-to-paraffin (O/P) ratio that limits hydrogen utilization efficiency. Herein, we report an unsaturated ZrO_x-modified iron catalyst (Na–Fe/a-ZrO₂) that delivers an olefin selectivity exceeding 80% among organic products, while suppressing the combined CO+CH₄ selectivity to below 25% and raising the O/P ratio to as high as ∼28. Multimodal in situ/operando spectroscopies and synchrotron-based vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS) demonstrate that unsaturated ZrO_x sites can modulate the activation modes of surface-bound *CO intermediates and selectively promote *CO insertion into alkyl species. This process consumes reactive intermediates that would otherwise desorb to form undesirable byproducts, thereby enabling selective olefin synthesis compatible with hydrogen-efficient CO₂ conversion.