First-principles and microkinetic simulation studies of CO2 hydrogenation mechanism and active site on MoS2 catalyst

[Display omitted] •CO2 + H2 mechanism and active site are studied by DFT and microkinetic modeling.•CO is exclusively formed via redox mechanism on S edge at 580–780 K, 1 bar, H2/CO2 = 1.•Rate determining step of CO2 hydrogenation at S edge on MoS2 is C-O scission in CO2.•CO formation rate: Mo edge > S edge > MoS2(001), meaning Mo edge as active site on MoS2.•The fundamental insights on MoS2 accelerate design of CO2 hydrogenation catalyst. Molybdenum disulphide (MoS2) has attracted much attention as a promising non-precious metal catalyst for CO2 hydrogenation to energy-rich commodities. However, the exact reaction mechanism and active site on the MoS2 catalyst are still a matter of debate. Using density functional theory (DFT) calculations and microkinetic modeling, we study the competitive pathways leading to the formation of CO, methane and methanol at the S edge site in MoS2 catalyst, and the results are compared to those on the Mo edge and MoS2(001) in our previous work. It is found that CO is exclusively produced through redox mechanism on the S edge at 580–780 K, 1 bar and H2/CO2 ratio of 1, with the rate determining step of C-O bond scission in CO2. The rate of CO formation follows the order of Mo edge > S edge > MoS2(001), suggesting the Mo edge as the likely active site on the MoS2 catalyst. This work offers a mechanistic understanding toward CO2 hydrogenation on the MoS2 catalyst at the atomic level, and the insights gained can be used to design improved catalysts for the CO2 and CO hydrogenation and other important reactions of technological interest.