Bandgap Shrinkage and Charge Transfer in 2D Layered SnS₂ Doped with V for Photocatalytic Efficiency Improvement

Abstract

Effects of electronic and atomic structures of V‐doped 2D layered SnS2 are studied using X‐ray spectroscopy for the development of photocatalytic/photovoltaic applications. Extended X‐ray absorption fine structure measurements at V K‐edge reveal the presence of VO and VS bonds which form the intercalation of tetrahedral OVS sites in the van der Waals (vdW) gap of SnS2 layers. X‐ray absorption near‐edge structure (XANES) reveals not only valence state of V dopant in SnS2 is ≈4+ but also the charge transfer (CT) from V to ligands, supported by V Lα,β resonant inelastic X‐ray scattering. These results suggest V doping produces extra interlayer covalent interactions and additional conducting channels, which increase the electronic conductivity and CT. This gives rapid transport of photo‐excited electrons and effective carrier separation in layered SnS2. Additionally, valence‐band photoemission spectra and S K‐edge XANES indicate that the density of states near/at valence‐band maximum is shifted to lower binding energy in V‐doped SnS2 compare to pristine SnS2 and exhibits band gap shrinkage. These findings support first‐principles density functional theory calculations of the interstitially tetrahedral OVS site intercalated in the vdW gap, highlighting the CT from V to ligands in V‐doped SnS2.

Mn3+ eg Configuration and Electron Transfer in Na-Incorporating α-MnO2 to Improve Electrochemical Supercapacitor: An In Situ and Ex Situ X-ray Absorption Spectroscopic Investigation

“…Thus, the valence state of the Mn ions in the α-MnO 2 in the charge–discharge process is quantitatively determined. According to the dipole-transition selection rule, the main absorption feature in the Mn K -edge XANES spectra is primarily associated with the Mn 1s → 4p transition, and the intensity of the threshold feature is attributable to the unoccupied Mn p–d hybridized states. , As observed in the literature on in-situ Mn K -edge XANES measurements of MnO 2 -related materials, , the threshold feature of α-MnO 2 [ x = 0.0 (Pristine) and 1.5] gradually shifts toward higher energies during the charging process from 0.0 to 0.5 and to 1.0 V, revealing an increase in the valence state of Mn ions with the operating potential. In contrast, the threshold feature shifts toward lower energies during the discharge process from 1.0 to r0.5 V to r0.0 V, indicating a decrease in the valence state of Mn ions in α-MnO 2 .…”

Interstitial/Substitutional Se Doping in Nanosheet Heterostructures for Sensing NH3: Experimental and Theoretical Study

“…Therefore, according to the Pauli exclusion principle and Hund rule, it is easier to form an adsorption model in which the N atom is adsorbed as a donor to the Sn atom as an acceptor. In contrast, the 2s and 2p orbitals of Sn in SnS 2 hybridize to form Sn 4+ , which form a stable molecular structure with the S atom, so the sulfur atom has two pairs of lone pairs of electrons as donors and empty orbitals of the H atom as acceptors to form ligands. , …”

“…In contrast, the 2s and 2p orbitals of Sn in SnS 2 hybridize to form Sn 4+ , which form a stable molecular structure with the S atom, so the sulfur atom has two pairs of lone pairs of electrons as donors and empty orbitals of the H atom as acceptors to form ligands. 55,56 As seen in Table 1, compared to SnS/SnS 2 , the E ad of NH 3 in the modified models of Se S −SnS/SnS 2 (SnS-TOP) and Se i − SnS/SnS 2 (SnS-TOP) is increased by nearly 2.90 and 3.18 times, respectively. The Se i −SnS/SnS 2 with the adsorption configuration of SnS-TOP displays the largest absolute E ad value (−0.701 eV), suggesting the most stable and preferential adsorption structure of NH 3 molecules on Se i −SnS/SnS 2 .…”

Photocatalysis with atomically thin sheets

“…The formation of these surface symmetry breakings ( e.g. , vacancy, 50,117,118 doping, 119,120 single atom, 121–124 cluster, 125,126 hetero-phase junction, 127,128 heterojunction, 129,130 and hole 131,132 or organic group 133 ) can lead to local polarization, thereby forming a qualitative polarized electric field. Under the action of this electric field, rapid separation and transfer of charges can be achieved.…”