Highly selective photothermal CO2 hydrogenation to C2+ hydrocarbons over Mn-modified K–Fe catalysts

Abstract

Efficient and selective CO₂ hydrogenation pathways are pivotal for tackling climate change while enabling sustainable energy solutions. Herein, we report a series of potassium-promoted Fe_xMn_y catalysts for the photothermal hydrogenation of CO₂ to C₂⁺ hydrocarbons under mild reaction conditions. By tuning the Fe/Mn ratio, we identify K–Fe₁₀Mn₁ as the optimal composition, exhibiting a remarkable C₂⁺ selectivity of 79.2% and a C_2-5 hydrocarbon yield of 4.8 mmol g⁻¹ h⁻¹ at 250 °C and 20 bar, under 4 W cm⁻² light irradiation. This catalyst also exhibited the lowest CO selectivity (24.1%) and the highest chain-growth probability (α = 0.64) among the series. In contrast, detailed characterization revealed that excessive Mn leads to over-stabilization of Fe₁Mn_1−xO species, diminishing the availability of active Fe₅C₂ species and reducing C–C coupling efficiency. Mechanistic studies, including in situ DRIFTS, demonstrate that non-thermal effects dominate the reaction pathway, with light irradiation accelerating the generation of key intermediates without altering the intrinsic mechanism. These findings provide fundamental insights into the structure–activity relationship of K–FeMn systems and offer a promising route for solar-driven CO₂-to-hydrocarbon conversion under industrially relevant conditions.