Methanol synthesis from H2 and CO2 on a Mo6S8 cluster: a density functional study

Area of Science:

• Catalysis
• Materials Science
• Computational Chemistry

Background:

• Catalytic CO(2) hydrogenation to methanol is crucial for CO(2) utilization.
• Molybdenum sulfide (MoS(2)) is a known catalyst, but its bulk and cluster forms exhibit different behaviors.
• Chevrel phase clusters like Mo(6)S(8) offer unique structural and electronic properties.

Purpose of the Study:

• To investigate the mechanism of methanol synthesis from CO(2) and H(2) on a Mo(6)S(8) cluster using density functional theory.
• To compare the catalytic pathway on the Mo(6)S(8) cluster with that of bulk MoS(2).
• To elucidate the factors contributing to the catalytic activity of the Mo(6)S(8) cluster.

Main Methods:

• Density Functional Theory (DFT) calculations.
• Investigation of reaction pathways and energy barriers for methanol synthesis.
• Analysis of electronic structure changes and bonding interactions.

Main Results:

• The Mo(6)S(8) cluster follows a different pathway than bulk MoS(2), which promotes C-O scission leading to hydrocarbons.
• The Mo(6)S(8) cluster is less reactive than bulk MoS(2) as it cannot cleave the C-O bond of H(x)CO intermediates.
• The Mo(6)S(8) cluster exhibits moderate activity for methanol synthesis via the reverse water-gas shift reaction followed by CO hydrogenation.
• The rate-limiting step is CO hydrogenation to HCO with a barrier of +1 eV, lower than that of Cu nanoparticles.
• Mo sites bind CO(2), CO, and CH(x)O, while S sites facilitate H-H bond cleavage.

Conclusions:

• The Mo(6)S(8) cluster is a viable catalyst for methanol synthesis from CO(2) and H(2).
• Its unique cagelike geometry and electronic structure (interplay of Mo d-band and S p-band) dictate its catalytic performance.
• The Mo(6)S(8) cluster offers a promising alternative to traditional catalysts like copper nanoparticles for methanol production.