Understanding Polyol Decomposition on Bimetallic Pt–Mo Catalysts—A DFT Study of Glycerol

Abstract

Catalytic dehydrogenation and C−C and C−O bond cleavage for glycerol decomposition on bimetallic Pt−Mo alloy model catalysts are studied using periodic density functional theory. The scaling relationship developed for monometallic systems for fast binding energy prediction has been tested and validated on both Ptskin and Pt 3 Mo-skin bimetallic surfaces. Using only the binding energies of atomic C and O for corresponding alloy surfaces, this simple relationship is shown to be an extremely efficient approach to speeding up the catalytic trend analysis for bimetallic alloy catalysts. Similar to Pt(111), it is found that the Pt-skin surface also favors dehydrogenation via C−H bond cleavage and faster C−C bond cleavage over C−O bond cleavage, but the overall activity decreases compared with pure Pt. On Pt 3 Mo-skin surfaces, the overall reaction becomes much more exothermic, but Mo species significantly affect the selectivity by favoring the C−O bond cleavage. Thermodynamic analyses also predict that surface Mo species can be easily oxidized under typical reforming conditions, forming molybdate clusters and severely altering surface structures and potentially catalytic properties. Guided by experimental observations, this study also explores possible bifunctional characteristics for Pt−Mo bimetallic catalysts responsible for improved reforming activity and hydrogen production rates.

Navigating Glycerol Conversion Roadmap and Heterogeneous Catalyst Selection Aided by Density Functional Theory: A Review

“…During the reaction, the metallic Mo content increases, indicating that these surface Mo oxide clusters are catalytically functional. This hypothesis has been confirmed with DFT calculations conducted by Liu et al [62]. During experiments, Pt-Mo catalyst particles can retain their Pt-rich core Mo-rich shell morphology [51].…”

“…If properly used, the modeling can be utilized to predict and tune catalytic properties for catalyst developments. Liu and Greeley [60,62,67,68] investigated adsorptions of glycerol and its dehydrogenation intermediates on transition metals. Adsorption patterns of glycerol conversion intermediates were investigated on close-packed surfaces of Pt, Ni, Pd, Rh, and Cu.…”

“…Despite the loss of H2 as Similar analyses can be performed on other transition metals or even bimetallic alloys [62,68]. It should be mentioned that acquiring full detail of the entire glycerol decomposition network is extremely, computationally expensive.…”

“…Most recently, periodic DFT calculations, coupled with fast energetic and kinetic analysis, have been employed to investigate glycerol decomposition on bimetallic Pt-Mo alloys [62]. It is concluded that on the Pt skin of Pt-Mo bimetallic alloys, CO binding becomes weaker and is able to promote reforming activity due to mitigated CO poisoning.…”

“…Many bimetallic alloys [34,40,48,49,62,81,83], metal-acid/support catalysts [75] can all establish multi-functional systems to influence reaction activity and product formation pathways.…”