Defect formation energies, electronic structures and optical properties of non-metal S, lanthanide metal Sc-doped and Sc–S co-doped anatase TiO
2
were systematically investigated via a GGA + U method ...based on density functional theory (DFT). The on-site Coulomb corrections were applied to both 3
d
orbitals of Ti atom (
U
Ti
_3
d
) and 2
p
orbitals of O atom (
U
O
_2
p
). The results show all doped TiO
2
systems exhibit a certain degree of red-shift due to the presence of impurity levels in the bandgap; in particular, the S-doped and Sc–S co-doped TiO
2
exhibit better light absorption properties in the visible light range than either pure or Sc-doped TiO
2
. In addition, the positive synergistic effect between the Sc and S atoms not only expands the absorption edge, but also increases the light absorption coefficient in the visible region. As a result, the Sc–S co-doped anatase TiO
2
shows the best optical absorption spectrum in all doping systems.
Graphical abstract
In view of the diverse functional groups left on the MXene during the etching process, we computationally investigated the effects of surface-group types on the structural, electronic and optical ...properties of Sc
CT
(T = -O, -OH, -F) MXenes. For all geometries of the Sc
CT
MXenes, the geometry I of Sc
CT
, which has the functional groups locating above the opposite-side Sc atoms, are lowest-energy structure. Accordingly, the energetically favorable Sc
CF
-I, Sc
CO
-I and Sc
C(OH)
-I were selected for further evaluation of the photocatalytic activities. We found that the Sc
CO
-I is metallic, while Sc
CF
-I and Sc
C(OH)
are semiconductors with visible-light absorptions and promising carrier mobilities. Compared with the Sc
C(OH)
-I, the Sc
CF
-I has not only more suitable band gap (1.91 eV), but also the higher redox capability of photo-activated carriers, which should have better photocatalytic performance.
Defect formation energies, electronic structures and optical properties of non- metal S, lanthanide metal Sc-doped and Sc-S co-doped anatase TiO.sub.2 were systematically investigated via a GGA + U ...method based on density functional theory (DFT). The on-site Coulomb corrections were applied to both 3d orbitals of Ti atom (U.sub.Ti_3d) and 2p orbitals of O atom (U.sub.O_2p). The results show all doped TiO.sub.2 systems exhibit a certain degree of red-shift due to the presence of impurity levels in the bandgap; in particular, the S-doped and Sc-S co-doped TiO.sub.2 exhibit better light absorption properties in the visible light range than either pure or Sc-doped TiO.sub.2. In addition, the positive synergistic effect between the Sc and S atoms not only expands the absorption edge, but also increases the light absorption coefficient in the visible region. As a result, the Sc-S co-doped anatase TiO.sub.2 shows the best optical absorption spectrum in all doping systems.
•CuCo2O4@RGO nanohybrid was prepared successfully.•The nanohybrid achieved a competitive PCE of 6.11%.•The sample offered a better electrochemical impedance.
In this article, the flower-like CuCo2O4 ...have been prepared by annealing treatment after a simple solvothermal technique, then dispersed on reduced graphene oxide (CuCo2O4@RGO) and applied as counter electrode (CE) in dye-sensitized solar cells (DSSCs). The DSSCs based on pure CuCo2O4 CE achieves a decent power conversion efficiency (PCE) of 5.19%, which has up to 84% of Pt CE (6.18%). However, after attaching RGO, the CuCo2O4@RGO nanohybrid obtains a competitive PCE of 6.11%. Through a series of electrochemical tests (Electrochemical impedance spectra, Tafel curve and cyclic voltammetry curve) and explaining the reason, the presence of RGO makes the nanohybrid possess a better catalytic activity than the pure CuCo2O4 and RGO. This work gives an alternative CE in non-Pt systems materials and a better choice in other related fields.
In this paper, the nanocomposites of the perovskite-phase La0.65Sr0.35MnO3 nanoparticles with reduced graphene oxide (LSMO@RGO) have been successfully prepared via the solution combustion method. ...LSMO@RGO nanocomposites exhibit excellent electrocatalytic performance for reduction of triiodide, owing to the positive synergetic effect between LSMO nanoparticles and RGO sheets. As a consequence, the dye-sensitized solar cell (DSSC) with the LSMO@RGO nanocomposites counter electrode (CE) yielded a power conversion efficiency (PCE) of 6.57%, which is observably higher than that of using pristine LSMO CE (5.35%) or RGO CE (4.93%) alone, and up to 92% of the Pt CE (7.13%).
•La0.65Sr0.35MnO3@RGO Nanocomposites were synthesized by solution combustion method.•The highest power conversion efficiency achieved 6.57%, reaching to 92% of Pt.•The cell possesses lower interface resistance.
Motivated by the successful synthesis of Janus monolayers of transition metal dichalcogenides ( i.e. , MoSSe), we computationally investigated the structural, electronic, optical, and transport ...properties of functionalized Janus MXenes, namely MM′CT 2 (M, M′ = Zr, Ti, Hf, M ≠ M′, T = –O, –F, –OH). The results of the calculations demonstrate that five stable O-terminated Janus MXenes (ZrTiCO 2 -I, ZrHfCO 2 -I, ZrHfCO 2 -III, HfTiCO 2 -I, and HfTiCO 2 -III), exhibit modest bandgaps of 1.37–1.94 eV, visible-light absorption (except for ZrHfCO 2 -I), high carrier mobility, and promising oxidization capability of photoinduced holes. Additionally, their indirect-gap, spatially separated electron–hole pairs, and the dramatic difference between the mobilities of electrons and holes could significantly limit the recombination of photoinduced electron–hole pairs. Our results indicate that the functionalized Janus MXene monolayers are ideal and promising materials for application in visible light-driven photocatalysis.
Motivated by the successful synthesis of Janus monolayers of transition metal dichalcogenides (i.e., MoSSe), we computationally investigated the structural, electronic, optical, and transport ...properties of functionalized Janus MXenes, namely MM′CT2 (M, M′ = Zr, Ti, Hf, M ≠ M′, T = –O, –F, –OH). The results of the calculations demonstrate that five stable O-terminated Janus MXenes (ZrTiCO2-I, ZrHfCO2-I, ZrHfCO2-III, HfTiCO2-I, and HfTiCO2-III), exhibit modest bandgaps of 1.37–1.94 eV, visible-light absorption (except for ZrHfCO2-I), high carrier mobility, and promising oxidization capability of photoinduced holes. Additionally, their indirect-gap, spatially separated electron–hole pairs, and the dramatic difference between the mobilities of electrons and holes could significantly limit the recombination of photoinduced electron–hole pairs. Our results indicate that the functionalized Janus MXene monolayers are ideal and promising materials for application in visible light-driven photocatalysis.
Searching for new two-dimensional (2D) Dirac cone materials has been popular since the discovery of graphene with a Dirac cone structure. Based on density functional theory (DFT) calculations, we ...theoretically designed a HfB
monolayer as a new 2D Dirac material by introducing the transition metal Hf into a graphene-like boron framework. This newly predicted HfB
monolayer has pronounced thermal and kinetic stabilities along with a Dirac cone with a massless Dirac fermion and Fermi velocities (3.59 × 10
and 6.15 × 10
m s
) comparable to that of graphene (8.2 × 10
m s
). This study enriches the diversity and promotes the application of 2D Dirac cone materials.
In this article, the flower-like CuCo2O4 have been prepared by annealing treatment after a simple solvothermal technique, then dispersed on reduced graphene oxide (CuCo2O4@RGO) and applied as counter ...electrode (CE) in dye-sensitized solar cells (DSSCs). The DSSCs based on pure CuCo2O4 CE achieves a decent power conversion efficiency (PCE) of 5.19%, which has up to 84% of Pt CE (6.18%). However, after attaching RGO, the CuCo2O4@RGO nanohybrid obtains a competitive PCE of 6.11%. Through a series of electrochemical tests (Electrochemical impedance spectra, Tafel curve and cyclic voltammetry curve) and explaining the reason, the presence of RGO makes the nanohybrid possess a better catalytic activity than the pure CuCo2O4 and RGO. This work gives an alternative CE in non-Pt systems materials and a better choice in other related fields
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