A DFT study of transition metal (Fe, Co, Ni, Cu, Ag, Au, Rh, Pd, Pt and Ir)-embedded monolayer MoS2 for gas adsorption

The structures and electronic properties of diverse transition metal (TM = Fe, Co, Ni, Cu, Ag, Au, Rh, Pd, Pt and Ir)-embedded monolayer MoS2 in the S-vacancy and the adsorption of various gas molecules (CO, NO, O2, NO2, NH3) have been systematically investigated using density functional theory (DFT). Our results show that strong interactions between the different transition metal atoms and S defect site in monolayer MoS2 suggest that the transition metal-embedded monolayer MoS2 should be stable. The embedded transition metal atoms can effectively modulate the electronic structures and magnetic properties of inert monolayer MoS2, and drastically enhance the adsorption and the activation of CO, NO, O2, NO2 and NH3 gas molecules, with respect to that on pristine monolayer MoS2 with weak physisorption. The electronic structure analysis reveals that introduced nd orbital impurity states of embedded transition metals in the band gap play an important role in the adsorption and effectively activation of gas molecules. In addition, obvious charge transfer occur from TM-MoS2 to oxidizing gas molecules (NO2, O2) acting as acceptors, whereas the direction of charge transfer is reversed for the adsorption of the reducing gas (NH3) as donor. Particularly, among all transition metal elements, embedded Fe and Co have better thermal stability, adsorption properties and chemical activities for gas molecules adsorption. Our results open new perspectives for the design and the study of high active MoS2-based 2D-nanomaterials.