4 research outputs found
Study on the Ambient Temperature as an Important but Easily Neglected Factor in the Process of Preparing Photovoltaic All-Inorganic CsPbIBr<sub>2</sub> Perovskite Film by the Elegant Solvent-Controlled Growth Strategy
All-inorganic CsPbIBr2 perovskite has received
extensive
attention in the field of solar cells due to its good wet and thermal
stability as well as a moderate band gap. In the preparation of CsPbIBr2 film by one-step spin-coating method, the amount of dimethyl
sulfoxide solvent remaining in the precursor film has a great influence
on the process of film growth. Therefore, it is necessary to ensure
that an appropriate amount of solvent exists in the precursor film
before annealing. Herein, we adopted the solvent-controlled growth
(SCG) strategy, that is, standing by the precursor films in the nitrogen
glovebox for a period of time before annealing, to make sure that
excess solvent can be evaporated from the precursor film. In this
work, we found that the ambient temperature is an important but easily
neglected factor in the process of preparing CsPbIBr2 film
by the SCG strategy. When the ambient temperature is 20 °C, SCG
treatment is required to obtain a flat and dense CsPbIBr2 film. However, SCG treatment is not essential at 30 °C. The
ambient temperature has an impact on the evaporation rate of the solvent
in the precursor film, and thus affects the effect of the SCG strategy.
This work highlights that, when preparing CsPbIBr2 film
by a one-step spin-coating method, in order to obtain a high-quality
CsPbIBr2 film, the influence of ambient temperature on
solvent-controlled growth strategy should be considered
Probing the Performance Limitations in Thin-Film FeVO<sub>4</sub> Photoanodes for Solar Water Splitting
FeVO<sub>4</sub> is
a potentially promising n-type multimetal oxide
semiconductor for photoelectrochemical water splitting based on its
favorable optical band gap of ca. 2.06 eV that allows for the absorption
of visible light up to around 600 nm. However, the presently demonstrated
photocurrent values on FeVO<sub>4</sub> photoanodes are yet considerably
low when comparing with α-Fe<sub>2</sub>O<sub>3</sub>, although
FeVO<sub>4</sub> can absorb comparable wavelengths of sunlight as
α-Fe<sub>2</sub>O<sub>3</sub>. Donor-type doping and constructing
nanoporous film morphology have afforded desirable (but far from satisfactory)
improvements in FeVO<sub>4</sub> photoanodes, whereas the fundamental
properties, such as absorption coefficients and the nature of optical
transition, and a quantitative analysis of the efficiency losses for
FeVO<sub>4</sub> photoanodes remain elusive. In the present study,
we conduct a thorough experimental analysis of structural, optical,
charge transport, and surface catalysis properties of FeVO<sub>4</sub> thin films to investigate and clarify how and where the efficiency
losses occur. Based on the results, the charge recombination pathways
and light-harvesting loss in FeVO<sub>4</sub> thin-film photoanodes
are identified and quantitatively determined. Our study will deepen
the understanding on the photoelectrochemical behaviors of FeVO<sub>4</sub> photoanodes and will also shed light on the optimization
routes to engineer this material to approach its theoretical maximum
Band Structure Engineering of Carbon Nitride: In Search of a Polymer Photocatalyst with High Photooxidation Property
The
electronic band structure of a semiconductor photocatalyst
intrinsically controls its level of conduction band (CB) and valence
band (VB) and, thus, influences its activity for different photocatalytic
reactions. Here, we report a simple bottom-up strategy to rationally
tune the band structure of graphitic carbon nitride (g-C<sub>3</sub>N<sub>4</sub>). By incorporating electron-deficient pyromellitic
dianhydride (PMDA) monomer into the network of g-C<sub>3</sub>N<sub>4</sub>, the VB position can be largely decreased and, thus, gives
a strong photooxidation capability. Consequently, the modified photocatalyst
shows preferential activity for water oxidation over water reduction
in comparison with g-C<sub>3</sub>N<sub>4</sub>. More strikingly,
the active species involved in the photodegradation of methyl orange
switches from photogenerated electrons to holes after band structure
engineering. This work may provide guidance on designing efficient
polymer photocatalysts with the desirable electronic structure for
specific photoreactions
High-Crystallinity Urchin‑like VS<sub>4</sub> Anode for High-Performance Lithium-Ion Storage
VS<sub>4</sub> anode
materials with controllable morphologies from
hierarchical microflower, octopus-like structure, seagrass-like structure
to urchin-like structure have been successfully synthesized by a facile
solvothermal synthesis approach using different alcohols as solvents.
Their structures and electrochemical properties with various morphologies
are systematically investigated, and the structure–property
relationship is established. Experimental results reveal that Li<sup>+</sup> ion storage behavior in VS<sub>4</sub> significantly depends
on physical features such as the morphology, crystallite size, and
specific surface area. According to this study, electrochemical performance
degrades on the order of urchin-like VS<sub>4</sub> > octopus-like
VS<sub>4</sub> > seagrass-like VS<sub>4</sub> > flower-like
VS<sub>4</sub>. Among them, urchin-like VS<sub>4</sub> demonstrates
the
best electrochemical performance benefiting from its peculiar structure
which possesses large surface area that accommodates the volume change
to a certain extent, and single-crystal thorns that provide fast electron
transportation. Kinetic parameters derived from EIS spectra and sweep-rate-dependent
CV curves, such as charge-transfer resistances, Li<sup>+</sup> ion
apparent diffusion coefficients and stored charge ratio of capacitive
and intercalation contributions, both support this claim well. In
addition, the EIS measurement was conducted during the first discharge/charge
process to study the solid electrolyte interface (SEI) formation on
urchin-like VS<sub>4</sub> and kinetics behavior of Li<sup>+</sup> ion diffusion. A better fundamental understanding on Li<sup>+</sup> storage behavior in VS<sub>4</sub> is promoted, which is applicable
to other vanadium-based materials as well. This study also provides
invaluable guidance for morphology-controlled synthesis tailored for
optimal electrochemical performance