Morphological and optical characterizations of Sb₂O₅ nanorods as new photoelectrode for hydrogen generation

Abstract

Sb2O5 nanorods were synthesized using vapor transport as a photoelectrode for
hydrogen generation. XRD revealed the formation of cubic Sb2O5 crystallographic
phase and no other impurity peaks were observed. The SEM images revealed
randomly oriented wedge shaped nanorods morphology. The optical band gap, the
refractive index and extinction coefficient of the synthesized Sb2O5 nanorods film
were calculated from the spectral transmittance and reflectance measurements. The
photocurrent density generated from Sb O2 5 nanorods film was – 0.055 mA/cm2 at -
0.88 V and it displayed a fast transient response in the on-off process of light. The
calculated hydrogen moles per active unit area was 0.48 μmole/h.cm2. The Sb2O5
nanorods photoelectrode have achieved an incident to photon conversion efficiency of
0.2 %. The results indicated that the Sb2O5 nanorods film could be used as a potential

Computational Prediction of an Antimony-Based n-Type Transparent Conducting Oxide: F-Doped Sb2O5

“…Indeed, an effective optical bandgap of ∼3.6 eV is predicted by determining the point at which the linear fit intersects the x -axis in the direct-gap Tauc plot ( Figure S2 ). We note that this aligns closely with the band gap of ∼3.55 eV from optical transmittance measurements by Mindil et al on cubic Sb 2 O 5 nanorod films; 41 however, no experimental measurement for C 2/ c monoclinic Sb 2 O 5 is known. Sb 2 O 5 has a centrosymmetric ( C 2/ c ) crystal structure, and so, it is likely that some of the low-energy optical transitions are symmetry-forbidden as in In 2 O 3 , 42 resulting in weak absorption just above the direct bandgap.…”

“…Due to the lack of low-energy-compensating acceptor species, the electron concentrations and Fermi levels under annealing and after cooling are mostly similar. The self-consistent Fermi level E F at room temperature is predicted to lie at 0.18 eV above the conduction band, assuming an annealing temperature of 700 °C. ,, The electron concentration at this predicted E F reaches 10 19 cm –3 , which is around 1 order of magnitude higher than the Mott criterion. At this carrier concentration, the predicted mobility and conductivity of F-doped Sb 2 O 5 are around 103 cm 2 V –1 s –1 and 100 S cm –1 , respectively, at room temperature, where the limiting scattering mechanism is mainly POP (Figure ).…”

“…The self-consistent Fermi level under O-poor conditions was predicted using the PY-SC-FERMI package. , An annealing/growth temperature of 700 °C was assumed as it is a widely reported growth temperature in the literature for Sb 2 O 5 synthesis. ,, To understand the defect behavior at operating (room) temperature, the “frozen defect approach” was applied where the total concentration of each defect is fixed to the equilibrium concentration at the annealing temperature. Upon cooling, the total concentration of each defect remains unchanged, whereas the relative populations of each defect charge state are allowed to re-equilibrate.…”

“…(b) Calculated self-consistent Fermi level positions in F-doped Sb 2 O 5 during annealing (gray) and upon cooling to operating temperature (300 K; black). The light blue block shows a range of growth temperatures from 500 to 700 °C reported in the literature. ,,, (c) Room-temperature carrier and defect concentrations as a function of annealing temperature. Defects with concentrations lower than 1 × 10 10 cm –3 are omitted from the legend and are plotted using DOPED and PY-SC-FERMI. ,, …”

“…The light blue block shows a range of growth temperatures from 500 to 700 °C reported in the literature. 16 , 41 , 65 , 69 (c) Room-temperature carrier and defect concentrations as a function of annealing temperature. Defects with concentrations lower than 1 × 10 10 cm –3 are omitted from the legend and are plotted using DOPED and PY-SC-FERMI.…”