Fig. 4: Characterizations and catalytic performance showing the impact of the FeO_x overlayer on CO₂ reduction.

Rh K-edge EXAFS spectra (a), isotherms of H₂ and CO₂ chemisorption (b, c), CO₂ conversion rates (d), and CO selectivity for CO₂ conversion (e), and the Arrhenius plots for CO₂ reduction to CO (f) for FeO_x/Rh/Fe₃O₄ and Rh/Fe₃O₄. Reaction conditions: 523–623 K, 101 kPa, CO₂/H₂/He = 7/28/105 mL min⁻¹ (gas hourly space velocity of 7 × 10⁵ mL g⁻¹ h⁻¹). The CO₂ and CO rates are normalized to the concentration of surface Rh as derived from EXAFS fitting.