4 research outputs found
Influence of TiO<sub>2</sub> Particle Size on Dye-Sensitized Solar Cells Employing an Organic Sensitizer and a Cobalt(III/II) Redox Electrolyte
Dye-sensitized
solar cells (DSSCs) are highly efficient and reliable
photovoltaic devices that are based on nanostructured semiconductor
photoelectrodes. From their inception in 1991, colloidal TiO<sub>2</sub> nanoparticles (NPs) with the large surface area have manifested
the highest performances and the particle size of around 20 nm is
generally regarded as the optimized condition. However, though there
have been reports on the influences of particle sizes in conventional
DSSCs employing iodide redox electrolyte, the size effects in DSSCs
with the state-of-the-art cobalt electrolyte have not been investigated.
In this research, systematic analyses on DSSCs with cobalt electrolytes
are carried out by using various sizes of NPs (20–30 nm), and
the highest performance is obtained in the case of 30 nm sized TiO<sub>2</sub> NPs, indicating that there is a reversed power conversion
efficiency trend when compared with those with the iodide counterpart.
Detailed investigations on various factorslight harvesting,
charge injection, dye regeneration, and charge collectionreveal
that TiO<sub>2</sub> particles with a size range of 20–30 nm
do not have a notable difference in charge injection, dye regeneration,
and even in light-harvesting efficiency. It is experimentally verified
that the superior charge collection property is the sole origin of
the higher performance, suggesting that charge collection should be
prioritized for designing nanostructured TiO<sub>2</sub> photoelectrodes
for DSSCs employing cobalt redox electrolytes
Highly Efficient Bifacial Dye-Sensitized Solar Cells Employing Polymeric Counter Electrodes
Dye-sensitized
solar cells (DSCs) are promising solar energy conversion
devices with aesthetically favorable properties such as being colorful
and having transparent features. They are also well-known for high
and reliable performance even under ambient lighting, and these advantages
distinguish DSCs for applications in window-type building-integrated
photovoltaics (BIPVs) that utilize photons from both lamplight and
sunlight. Therefore, investigations on bifacial DSCs have been done
intensively, but further enhancement in performance under back-illumination
is essential for practical window-BIPV applications. In this research,
highly efficient bifacial DSCs were prepared by a combination of electropolymerized
poly(3,4-ethylenedioxythiphene) (PEDOT) counter electrodes (CEs) and
cobalt bipyridine redox ([Co(bpy)<sub>3</sub>]<sup>3+/2+</sup>) electrolyte,
both of which manifested superior transparency when compared with
conventional Pt and iodide counterparts, respectively. Keen electrochemical
analyses of PEDOT films verified that superior electrical properties
were achievable when the thickness of the film was reduced, while
their high electrocatalytic activities were unchanged. The combination
of the PEDOT thin film and [Co(bpy)<sub>3</sub>]<sup>3+/2+</sup> electrolyte
led to an unprecedented power conversion efficiency among bifacial
DSCs under back-illumination, which was also over 85% of that obtained
under front-illumination. Furthermore, the advantage of the electropolymerization
process, which does not require an elevation of temperature, was demonstrated
by flexible bifacial DSC applications
Understanding the Bifunctional Effect for Removal of CO Poisoning: Blend of a Platinum Nanocatalyst and Hydrous Ruthenium Oxide as a Model System
CO
poisoning of Pt catalysts is one of the most critical problems
that deteriorate the electrocatalytic oxidation and reduction reactions
taking place in fuel cells. In general, enhancing CO oxidation properties
of catalysts by tailoring the electronic structure of Pt (electronic
effect) or increasing the amount of supplied oxygen species (bifunctional
effect), which is the typical reactant for CO oxidation, has been
performed to remove CO from the Pt surface. However, though there
have been a few reports about the understanding of the electronic
effect for rapid CO oxidation, a separate understanding of bifunctional
modification is yet to be achieved. Herein, we report experimental
investigations of CO oxidation in the absence of electronic effect
and an extended concept of the bifunctional effect. A model system
was prepared by blending conventional Pt/C catalysts with hydrous
ruthenium oxide particles, and the CO oxidation behaviors were investigated
by various electrochemical measurements, including CO stripping and
bulk oxidation. In addition, this system allowed the observation of
CO removal by the Eley–Rideal mechanism at high CO coverages,
which facilitates further CO oxidation by triggering the CO removal
by the Langmuir–Hinshelwood mechanism. Furthermore, effective
CO management by this approach in practical applications was also
verified by single-cell analysis
High-Density Single-Layer Coating of Gold Nanoparticles onto Multiple Substrates by Using an Intrinsically Disordered Protein of α‑Synuclein for Nanoapplications
Functional
graffiti of nanoparticles onto target surface is an
important issue in the development of nanodevices. A general strategy
has been introduced here to decorate chemically diverse substrates
with gold nanoparticles (AuNPs) in the form of a close-packed single
layer by using an omni-adhesive protein of α-synuclein (αS)
as conjugated with the particles. Since the adsorption was highly
sensitive to pH, the amino acid sequence of αS exposed from
the conjugates and its conformationally disordered state capable of
exhibiting structural plasticity are considered to be responsible
for the single-layer coating over diverse surfaces. Merited by the
simple solution-based adsorption procedure, the particles have been
imprinted to various geometric shapes in 2-D and physically inaccessible
surfaces of 3-D objects. The αS-encapsulated AuNPs to form a
high-density single-layer coat has been employed in the development
of nonvolatile memory, fule-cell, solar-cell, and cell-culture platform,
where the outlying αS has played versatile roles such as a dielectric
layer for charge retention, a sacrificial layer to expose AuNPs for
chemical catalysis, a reaction center for silicification, and biointerface
for cell attachment, respectively. Multiple utilizations of the αS-based
hybrid NPs, therefore, could offer great versatility to fabricate
a variety of NP-integrated advanced materials which would serve as
an indispensable component for widespread applications of high-performance
nanodevices