Formation of (Rh–Fe)–FeOx Complex Sites Enables Methanol Synthesis from CO₂

We addressed the challenges of designing catalysts for selective CO2 hydrogenation by incorporating Fe oxide species onto Rh nanoparticles. Nanoscopic FeOx domains created a "reverse catalyst" structure (i.e., a metal oxide supported on a metal) that increased the density of interfacial sites compared to traditional supported catalysts. The contact between the metal nanoparticle and the oxide overlayer induced the formation of a surface Rh–Fe alloy that stabilized methoxy groups while suppressing hydrogenolysis to methane. Sites at FeOx–metal interfaces interact with CO2 much stronger than sites on metal surfaces, show larger energy barriers to cleave the C–O bonds, and offer a barrierless pathway for the hydrogenation of methoxy species to methanol. Consequently, the multifunctional sites over FeOx/Rh–Fe catalysts highlight and meet the requirements of a selective methanol catalyst: strong interaction with CO2 to ensure a high density of transition states, metal sites to activate and make hydrogen available to surface intermediates, and high energy barriers for C–O bond cleavage to form carbides. These synthetic and catalytic chemistries, demonstrated for Rh–Fe–FeOx interfaces, enable us to overcome the limitations to the design of methanol production catalysts.