70 research outputs found
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High green density ceramic components fabricated by the slurry-based 3DP process
The 3DP process has been modified to directly fabricate high green density parts using
submicron powder. The slurry-based 3DP process deposits the powder bed by spraying a
dispersed slurry of the component material onto a piston. Alumina, silicon nitride, and
lead zirconate titanate components with green densities as high as 67% have been
fabricated by the slurry-based 3DP process. Solution phase binder systems have proven
to be successful for the new process. Substantially improved surface finish over the
conventional dry powder-based 3DP process has been demonstrated. Layer heights less
than 50 Jlm can be prepared with this process. Thus, the stepped surface topography
commonly observed in solid free form parts is substantially reduced.Mechanical Engineerin
Strategies for enhancing the photocurrent, photovoltage, and stability of photoelectrodes for photoelectrochemical water splitting
To accelerate the deployment of hydrogen produced by renewable solar energy, several technologies have been competitively developed, including photoelectrochemical (PEC), photocatalytic, and photovoltaic-electrolysis routes. In this review, we place PEC in context with these competing technologies and highlight key advantages of PEC systems. After defining the unique performance metrics of the PEC water splitting system, recently developed strategies for enhancing each performance metric, such as the photocurrent density, photovoltage, fill factor, and stability are surveyed in conjunction with the relevant theoretical aspects. In addition, various advanced characterization methods are discussed, including recently developed in situ techniques, allowing us to understand not only the basic properties of materials but also diverse photophysical phenomena underlying the PEC system. Based on the insights gained from these advanced characterization techniques, we not only provide a resource for researchers in the field as well as those who want to join the field, but also offer an outlook of how thin film-based PEC studies could lead to commercially viable water splitting systems
Formation of yttria-stabilized zirconia nanotubes by atomic layer deposition toward efficient solid electrolytes
Abstract We describe a fabrication strategy for preparing yttria-stabilized zirconia nanotube (YSZ-NT) arrays embedded in porous alumina membranes by means of template-directed atomic layer deposition (ALD) technique. The individual YSZ-NTs have a high aspect-ratio of well over 120, about ~ 110 nm in diameter, and ~ 14 µm in length. Interfacing the tube arrays with porous Pt was also introduced on the basis of partial etching technique in order to construct Pt/YSZ-NTs/Pt membrane electrode assembly (MEA) structures. The resulting YSZ-NTs MEAs show a 7 mm in diameter with a roughness factor of ~ 2. Area specific resistance was measured up to 1.84 Ω cm2 at 400 °C using H2 as fuel
Direct methane solid oxide fuel cells based on catalytic partial oxidation enabling complete coking tolerance of Ni-based anodes
Solid oxide fuel cells (SOFCs) can oxidize diverse fuels by harnessing oxygen ions. Benefited by this feature, direct utilization of hydrocarbon fuels without external reformers allows for cost-effective realization of SOFC systems. Superior hydrocarbon reforming catalysts such as nickel are required for this application. However, carbon coking on nickel-based anodes and the low efficiency associated with hydrocarbon fueling relegate these systems to immature technologies. Herein, we present methane-fueled SOFCs operated under conditions of catalytic partial oxidation (CPOX). Utilizing CPOX eliminates carbon coking on Ni and facilitates the oxidation of methane. Ni-gadolinium-doped ceria (GDC) anode-based cells exhibit exceptional power densities of 1.35 W cm−2 at 650 °C and 0.74 W cm−2 at 550 °C, with stable operation over 500 h, while the similarly prepared Ni-yttria stabilized zirconia anode-based cells exhibit a power density of 0.27 W cm−2 at 650 °C, showing gradual degradation. Chemical analyses suggest that combining GDC with the Ni anode prevents the oxidation of Ni due to the oxygen exchange ability of GDC. In addition, CPOX operation allows the usage of stainless steel current collectors. Our results demonstrate that high-performance SOFCs utilizing methane CPOX can be realized without deterioration of Ni-based anodes using cost-effective current collectors
Enhanced Photocurrent of Transparent CuFeO<sub>2</sub> Photocathodes by Self-Light-Harvesting Architecture
Efficient
sunlight-driven water-splitting devices can be achieved by using an
optically and energetically well-matched pair of photoelectrodes in
a tandem configuration. The key for maximizing the photoelectrochemical
efficiency is the use of a highly transparent front photoelectrode
with a band gap below 2.0 eV. Herein, we propose two-dimensional (2D)
photonic crystal (PC) structures consisting of a CuFeO<sub>2</sub>-decorated microsphere monolayer, which serve as self-light-harvesting
architectures allowing for amplified light absorption and high transparency.
The photocurrent densities are evaluated for three CuFeO<sub>2</sub> 2D PC-based photoelectrodes with microspheres of different sizes.
The optical analysis confirmed the presence of a photonic stop band
that generates <i>slow light</i> and at the same time amplifies
the absorption of light. The 410 nm sized CuFeO<sub>2</sub>-decorated
microsphere 2D PC photocathode shows an exceptionally high visible
light transmittance of 76.4% and a relatively high photocurrent of
0.2 mA cm<sup>–2</sup> at 0.6 V vs a reversible hydrogen electrode.
The effect of the microsphere size on the carrier collection efficiency
was analyzed by in situ conductive atomic force microscopy observation
under illumination. Our novel synthetic method to produce self-light-harvesting
nanostructures provides a promising approach for the effective use
of solar energy by highly transparent photocathodes
Highly Transparent Low Resistance ZnO/Ag Nanowire/ZnO Composite Electrode for Thin Film Solar Cells
We present an indium-free transparent conducting composite electrode composed of silver nanowires (AgNWs) and ZnO bilayers. The AgNWs form a random percolating network embedded between the ZnO layers. The unique structural features of our ZnO/AgNW/ZnO multilayered composite allow for a novel transparent conducting electrode with unprecedented excellent thermal stability (∼375 °C), adhesiveness, and flexibility as well as high electrical conductivity (∼8.0 Ω/sq) and good optical transparency (>91% at 550 nm). Cu(In,Ga)(S,Se)<sub>2</sub> (CIGSSe) thin film solar cells incorporating this composite electrode exhibited a 20% increase of the power conversion efficiency compared to a conventional sputtered indium tin oxide-based CIGSSe solar cell. The ZnO/AgNW/ZnO composite structure enables effective light transmission and current collection as well as a reduced leakage current, all of which lead to better cell performance
Materials for chiral light control
International audienceSolution-processable semiconductors based on small molecules, polymers or halide perovskites combine sustainable manufacturing with exceptional optoelectronic properties that can be chemically tailored to achieve flexible and highly efficient optoelectronic and photonic devices. A new exciting research direction is the study of the influence of chirality on light-matter interactions in these soft materials and its exploitation for the simultaneous control of charge, spin and light. In this Viewpoint, researchers working on different types of chiral semiconductors discuss the most interesting directions in this rapidly expanding field
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