Carbon dioxide (CO2) recycling as a feedstock for producing chemicals contributes to hinder the greenhouse effect caused by the increasing CO2 emissions. Hydrogenation of CO2 to synthesize methanol (CO2 + 3H2 ® CH3OH + H2O) has attracted considerable interests. This reaction is of great industrial importance because CH3OH has been proposed as an alternative energy source and is an important resource to synthesize organic compounds. Bare MoS2 nanoparticles and edge surfaces convert syngas only to hydrocarbons. The promoters are found necessary for the higher sulfur- and coke-resistance, and better selectivity to higher alcohols. In the present talk, DFT calculations were performed to investigate the CH3OH synthesis from CO2 and H2 on a model Mo6S8 cluster modified by various metals (M = K, Ti, Ni, Co, Cu, and Rh), aiming to understand the behaviors of Mo, S and M during the methanol synthesis and improve the activity of Mo6S8. Our study showed that by adopting a unique conformation a model Mo6S8 cluster displayed high selectivity to CH3OH and the CH3OH production was likely to be higher than pure Cu, while the cluster both in gas phase and supported on Au(111) stayed intact in interaction with the adsorbates. However, the overall conversion of CO2 was much lower than that of MoS2, which was associated with weaker binding and therefore higher barrier for bond breaking due to the higher S/Mo ratio. Using K as a modifier is able to accelerate the methanol synthesis on Mo6S8 the most; while the promotion by Rh is relatively small. Using the modifiers like Ti, Co, Ni, and Cu, the activity of Mo6S8 is decreased instead. The relative stability between *HCOO and *HOCO is identified as a descriptor to capture the variation in mechanism and scales well with the estimated activity. Our study not only provides better understanding of the reaction mechanism and actives on the modified Mo6S8, but also predicts some possible candidates, which can be used a promoter to facilitate the CH3OH synthesis on Mo sulfides.

Mechanistic study of methanol synthesis from CO2 and H2 on a modified model Mo sulfide-based catalysts

251st National Meeting (2016)

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