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MoS2 monolayer catalyst doped with isolated Co atoms for the hydrodeoxygenation reaction

Abstract

The conversion of oxygen-rich biomass into hydrocarbon fuels requires efficient hydrodeoxygenation catalysts during the upgrading process. However, traditionally prepared CoMoS2 catalysts, although efficient for hydrodesulfurization, are not appropriate due to their poor activity, sulfur loss and rapid deactivation at elevated temperature. Here, we report the synthesis of MoS2 monolayer sheets decorated with isolated Co atoms that bond covalently to sulfur vacancies on the basal planes that, when compared with conventionally prepared samples, exhibit superior activity, selectivity and stability for the hydrodeoxygenation of 4-methylphenol to toluene. This higher activity allows the reaction temperature to be reduced from the typically used 300 °C to 180 °C and thus allows the catalysis to proceed without sulfur loss and deactivation. Experimental analysis and density functional theory calculations reveal a large number of sites at the interface between the Co and Mo atoms on the MoS2 basal surface and we ascribe the higher activity to the presence of sulfur vacancies that are created local to the observed Co–S–Mo interfacial sites.

Figure 1: Superior activity and stability of Co–SMoS2.
Figure 2: Chemical characterization and identification of the Co atom in fresh Co–SMoS2 by EXAFS and HAADF–STEM and EELS.
Figure 3: Detailed atomic resolution HAADF–STEM characterization of the basal plane of used Co–SMoS2.
Figure 4: DFT optimized geometries of the three Co binding configurations and the energetics of how the Co–S–Mo interface promotes the formation of more sulfur vacancy sites.

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Acknowledgements

We acknowledge financial support from the EPSRC research council, UK. The authors wish to thank the National Synchrotron Radiation Center, Hsinchu, Taiwan (Y.-L. Soo and T.-S. Wu) for access to EXAFS facilities. A.W.R acknowledges financial support from KIER (B6-2452). Y.C.L. and K.S. thank the JST Research Acceleration Programme for support. The authors also acknowledge the use of the UCL Legion High Performance Computing Facilities Legion@UCL and Grace@UCL, and associated support services, in the completion of the theoretical portion of this work. The authors thank the financial support of CSC scholarship to G.L. and Swire scholarship to M.M.-J.L. to work at Oxford University.

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G.L. performed synthesis, catalyst testing and material characterizations; M.M.-J.L. carried out EXAFS analysis; W.C.H.K. carried out HAADF–STEM analysis; A.W.R. and J.H.W. performed AC–TEM analysis; A.W.R., Y.C.L. and K.S. for STEM–EELS analysis; M.T.D., M.H.M. and M.S. for DFT calculations; G.L., A.W.R. and S.C.E.T. wrote the main text; all authors discussed and reviewed this paper. S.C.E.T. planned, supervised and led the project.

Corresponding author

Correspondence to Shik Chi Edman Tsang.

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The authors declare no competing financial interests.

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Liu, G., Robertson, A., Li, MJ. et al. MoS2 monolayer catalyst doped with isolated Co atoms for the hydrodeoxygenation reaction. Nature Chem 9, 810–816 (2017). https://doi.org/10.1038/nchem.2740

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