Exploration of high-performance W6S8-supported single-atom Rh-1 catalysts for reverse water-gas shift reaction and methanol formation via DFT computational study

Exploration of highly selective catalysts for the reverse water-gas shift reaction, which can achieve an economical CO2 hydrogenation, still remains an urgent and challenging task. Here, for the first time, we offer a guideline of this task that single-atom catalysts (SAC) exhibit unusual catalytic properties and provide an ideal platform for reducing noble-metal usage. In the present study, we identified the single-atom catalysts, namely Rh-1@W6S8, by means of density functional theory (DFT) computations, aiming at developing even more efficient and low-cost catalysts for RWGS reaction, which exhibit improved overall catalytic performance compared to W6S8 for the RWGS reaction via four mechanisms. The energetic span model (ESM) is applied to evaluate the efficiency of the four mechanisms. Our results reveal that mechanism C, the CO2 with the hydrogen atoms from dissociated hydrogen to yield the HCOOH* intermediate, which dissociates subsequently to generate CO and water on a single-atom Rh-1@W6S8 catalyst is the most suitable pathway for RWGS with lowest rate-determining energy barrier. Simultaneously, our work clearly shows that in comparison with the W6S8 or Rh-1@Mo6S8, the Rh-1@W6S8 has higher catalytic activity and highest TOF value. DFT calculations demonstrate that Rh-1@W6S8 promote the CO2 hydrogenation to CH3OH via the reverse water-gas-shift (RWGS) reaction to produce CO followed by Its hydrogenation to CH3OH through the formation of methoxy (CH3O*) as a reaction intermediate and the Rh-1@W6S8 is beneficial for the synthesis of methanol. In summary, this work could provide insights on the significant role of a single metal atom on RWGS reaction and a variety of industrial chemical reactions. (C) 2018 Elsevier Ltd. All rights reserved.