XPS experimental and DFT investigations on solid solutions of Mo_1−xRe_xS₂ (0 < x < 0.20)

Abstract

The synthesis, characterization, experimental X-ray photoelectron spectra (XPS) and density-functional theory (DFT) investigations on solid solutions of Mo1-xRexS2 (x = 0.05, 0.10, 0.15 and 0.20) are reported herein. It is shown that even at a low concentration of dopant Re atoms, clustering occurs. At an Re concentration of 5% the formation of dimer-like impregnations is observed. An increase in the dopant concentration leads to an increase in the amount of clustered rhenium atoms and to the formation of rhombic clusters. The absence of magnetism within the studied Mo1-xRexS2 solid solutions allowed us to suggest a mechanism for the distribution of rhenium inside molybdenum disulphide through the initial formation of rhenium disulphide and its subsequent spreading.

Extending the Colloidal Transition Metal Dichalcogenide Library to ReS2 Nanosheets for Application in Gas Sensing and Electrocatalysis

“…It is interesting to note that in the LPE and bulk cases, the S 2p signal can be decomposed in two different doublets, corresponding to two different chemical environments of sulfur. Similar results have been reported by Dalmatova et al, and the two S components have been assigned to ReS 2 (doublet at lower binding energy, with S 2p 3/2 component at ≈161.4 eV) and to S atoms that are not connected to Re atoms (doublet at higher binding energy, with S 2p 3/2 component at ≈162.1 eV). However, we cannot discard that the two S components come from the existence of different ReS bond lengths in the distorted ReS 2 structure, as illustrated in Scheme d .…”

Electrochemical Hydrogen Evolution over Hydrothermally Synthesized Re-Doped MoS2 Flower-Like Microspheres

“…These results, together with those of HAADF-STEM analysis, confirm a substitutional n-type Re doping on the MoS 2 structure and are consistent with previously synthesized Re-doped MoS 2 materials [33]. The sample with the highest amount of rhenium (39.2% Re-MoS 2 ) shows the most broadened spectra, having an additional low-energy component obtained by the deconvolution of the Mo 3d and S 2p spectra (Figure 5b,c), which suggests the presence of two kinds of molybdenum species [19]. This component at low binding energy can be considered as a contribution of structural defects or due to disordered structures close to the metastable 1T-MoS 2 configuration among a 2H-MoS 2 phase [19].…”

“…As it can been seen in Figure 1c,d, more discrete particles are observed for samples with higher rhenium content, with an average diameter of 1.63 µm for the 39.2% Re-doped MoS2 sample (Figure 1d). Higher magnification of the nanosheets reveals the Re-doped samples to have a smaller lateral size than that of the undoped sample, with the smallest size for the 39.2% Re-MoS2 sample (Insets Figure 1a- Figure 2, the XRD profiles of pristine and doped samples look very similar, showing a single-phase with four reflections at approximately 2 θ = 14.3, 33.2, 39.5, and 58.7° corresponding, respectively, to (002), (100), (103), and (110) planes of 2H-phase MoS2 polytype (JCPDS 37-1492) [19,23]. Dominance of 2H-MoS2 diffraction peaks makes it difficult to determine the presence of the 1Td-ReS2 phase (which has a particularly disordered lattice structure) in all XRD sample patterns [23].…”

“…The sample with the highest amount of rhenium (39.2% Re-MoS2) shows the most broadened spectra, having an additional low-energy component obtained by the deconvolution of the Mo 3d and S 2p spectra (Figure 5b,c), which suggests the presence of two kinds of molybdenum species [19]. This component at low binding energy can be considered as a contribution of structural defects or due to disordered structures close to the metastable 1T-MoS2 configuration among a 2H-MoS2 phase [19]. Figure 5d shows the Re 4f7/2 and 4f5/2 binding energy peaks for the 14.7%, 29.7%, and 39.2% Re-doped MoS2 samples, which confirms the presence of Re 4+ in all the Re-doped samples [30].…”

“…Doping with non-metallic or transition metals atoms into the MoS 2 structure activates both edges and basal plane, improving the electronic mobility, charge transportability, and catalytically active surface area, therefore enhancing HER activity of the material [12][13][14][15]. In this sense, rhenium doping has been proposed to tune the electronic structure and polymorphic phases and to activate the basal planes of MoS 2 [16][17][18][19]. It has been demonstrated that a low concentration Re (n-type) doping induces broader valence bands and electron accumulation close to the Fermi level in MoS 2 fullerenes, resulting in a better HER performance [20].…”