<p>The hydrogenation of CO₂ to CH₄ was studied over a series of Mg-promoted Fe catalysts containing 2&#xa0;wt% Mg. The catalysts were synthesized using different preparation methods and Mg precursors to systematically assess the impact of bulk and surface properties on catalytic behavior. Comprehensive characterization was performed using X-ray diffraction, N₂ physisorption, ⁵⁷Fe Moessbauer spectroscopy, X-ray photoelectron spectroscopy, temperature-programmed reduction by H₂, temperature-programmed desorption of NH₃ and temperature-programmed hydrogenation. Structure–activity relations indicate that a homogeneous Mg distribution in the bulk enhances the formation of surface defects and amorphous phases, while improving the reducibility of the fresh catalysts. These characteristics promote the formation of iron carbide and carbonaceous surface species, which are identified as the active phases responsible for CH₄ formation during CO₂ hydrogenation. The reverse water–gas shift reaction was found to be a key step driving CO₂ activation. The catalyst prepared by flame spray pyrolysis using magnesium acetate as precursor exhibited the highest performance. Under industrially relevant conditions (400&#xa0;°C, 14&#xa0;bar, 8500&#xa0;h⁻¹), a CO₂ conversion of 68% and a CH₄ selectivity of 78% were achieved, representing the highest efficiency reported to date for Fe-based catalysts.</p>