Interplay between Surface Reconstruction and Redox State related to the CO₂ Activation on α-Fe₂O₃(012) single-crystal surfaces

Although Fe reduction is frequently linked to CO₂ activation on iron oxides, it remains unclear whether reactivity originates from the oxidation state itself or from the local environment in which reduced Fe species are formed. Here, near-ambient-pressure X-ray photoelectron spectroscopy combined with low-energy electron diffraction is used to address this question by comparing CO₂ activation on two well-defined α-Fe₂O₃(012) surface terminations with distinct local Fe environments. On the (1×1) termination, H₂ exposure induces partial surface reduction and generates Fe²⁺ species that enable subsequent CO₂ activation, leading to the formation of activated CO⁻ intermediates identified by a C 1s feature at 288.7 eV. In contrast, the reconstructed (2×1) termination does not promote charge-transfer-mediated CO₂ activation despite the presence of Fe²⁺ species; instead, CO₂ exposure favors bicarbonate formation and re-oxidizes surface Fe²⁺ to Fe³⁺. This termination-dependent response demonstrates that CO₂ activation on α-Fe₂O₃(012) is governed not only by Fe oxidation state but also by the local environment in which reduced Fe species are stabilized. These findings establish that reduced Fe sites become reactive only in specific surface environments, providing mechanistic insight into the structure–reactivity relationships governing CO₂ activation on iron oxide catalysts.