No abstract

In 2 O 3 has recently emerged as a promising catalyst for methanol synthesis from CO 2 . In this work, we present the promotional effect of Pd on this catalyst and investigate structure−performance relationships using in situ X-ray spectroscopy, ex situ characterization, and microkinetic modeling. Catalysts were synthesized with varying In:Pd ratios (1:0, 2:1, 1:1, 1:2, 0:1) and tested for methanol synthesis from CO 2 /H 2 at 40 bar and 300 °C. In:Pd(2:1)/SiO 2 shows the highest activity (5.1 μmol MeOH/g InPd s) and selectivity toward methanol (61%). While all bimetallic catalysts had enhanced catalytic performance, characterization reveals methanol synthesis was maximized when the catalyst contained both In−Pd intermetallic compounds and an indium oxide phase. Experimental results and density functional theory suggest the active phase arises from a synergy between the indium oxide phase and a bimetallic In−Pd particle with a surface enrichment of indium. We show that the promotion observed in the In−Pd system is extendable to non precious metal containing binary systems, in particular In−Ni, which displayed similar composition−activity trends to the In−Pd system. Both palladium and nickel were found to form bimetallic catalysts with enhanced methanol activity and selectivity relative to that of indium oxide.