Correction to: Moth-eye Structured Polydimethylsiloxane Films for High-Efficiency Perovskite Solar Cells

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Reinforced Nafion Membrane with Ultrathin MWCNTs/Ceria Layers for Durable Proton-Exchange Membrane Fuel Cells

For further commercializing proton-exchange membrane fuel cells, it is crucial to attain long-term durability while achieving high performance. In this study, a strategy for modifying commercial Nafion membranes by introducing ultrathin multiwalled carbon nanotubes (MWCNTs)/CeO2 layers on both sides of the membrane was developed to construct a mechanically and chemically reinforced membrane electrode assembly. The dispersion properties of the MWCNTs were greatly improved through chemical modification with acid treatment, and the mixed solution of MWCNTs/CeO2 was uniformly prepared through a high-energy ball-milling process. By employing a spray-coating technique, the ultrathin MWCNTs/CeO2 layers were introduced onto the membrane surfaces without any agglomeration problem because the solvent rapidly evaporated during the layer-by-layer stacking process. These ultrathin and highly dispersed MWCNTs/CeO2 layers effectively reinforced the mechanical properties and chemical durability of the membrane while minimizing the performance drop despite their non-ion-conducting properties. The characteristics of the MWCNTs/CeO2 layers and the reinforced Nafion membrane were investigated using various in situ and ex situ measurement techniques; in addition, electrochemical measurements for fuel cells were conducted

Multifunctional Moth-Eye TiO₂/PDMS Pads with High Transmittance and UV Filtering

This work reports a facile fabrication method for constructing multifunctional moth-eye TiO₂/polydimethylsiloxane (PDMS) pads using soft nano-imprinting lithography and a gas-phase-deposited thin sacrificial layer. Mesoporous TiO₂ nanoparticles act as an effective UV filter, completely blocking high-energy UVB light and partially blocking UVA light and forming a robust TiO₂/PDMS composite pad by allowing the PDMS solution to easily fill the porous TiO₂ network. The paraboloid-shaped moth-eye nanostructures provided high transparency in the visible spectrum and also have self-cleaning effects because of nanoroughness on the surface. Furthermore, we successfully achieved a desired multiscale-patterned surface by partially curing select regions using TiO₂/PDMS pads with partial UVA ray blockers. The ability to fabricate multifunctional polymeric pads is advantageous for satisfying increasing demands for flexible and wearable electronics, displays, and solar cells

Multifunctional Moth-Eye TiO₂/PDMS Pads with High Transmittance and UV Filtering

This work reports a facile fabrication method for constructing multifunctional moth-eye TiO₂/polydimethylsiloxane (PDMS) pads using soft nano-imprinting lithography and a gas-phase-deposited thin sacrificial layer. Mesoporous TiO₂ nanoparticles act as an effective UV filter, completely blocking high-energy UVB light and partially blocking UVA light and forming a robust TiO₂/PDMS composite pad by allowing the PDMS solution to easily fill the porous TiO₂ network. The paraboloid-shaped moth-eye nanostructures provided high transparency in the visible spectrum and also have self-cleaning effects because of nanoroughness on the surface. Furthermore, we successfully achieved a desired multiscale-patterned surface by partially curing select regions using TiO₂/PDMS pads with partial UVA ray blockers. The ability to fabricate multifunctional polymeric pads is advantageous for satisfying increasing demands for flexible and wearable electronics, displays, and solar cells

Reusable and Transparent Impaction‐Based Filter with Micro Apertured Multiscale Polymeric Stencil for Particulate Matter Capture

Abstract Air pollution by particulate matter (PM) in the air including PM1.0, PM2.5, and PM10, which are categorized by particle size, is a critical global environmental issue, harming the climate, ecosystems, and human health. Especially, ultrafine dust including PM1.0 and PM2.5 poses significant human health risks. Commercial fabric‐based filters effectively trap PMs but cause high‐pressure drop and limited filter capacity and reusability. Electrospun nanofiber filters address some issues but have low mechanical strength, toxic exposure risks, long fabrication times, and restrained reusability. Herein, a reusable and transparent impaction‐based PM filter using a UV‐curable polymeric stencil with micro apertures is proposed. The polymeric stencil filters achieve high filter efficiency (68–94%), superior filter capacity, and low‐pressure drop (<64 Pa). The polymeric stencil filters can be easily cleaned with water or ethanol and remain stable under extreme temperatures (−196 to 450 °C) with slight shrinkage (0–7%). The polymeric stencil filters can be broadly utilized for not only industrial, indoor, and vehicle filters but also transparent and flexible facial health masks

Fabrication of an Ionomer-Free Electrode Containing Vertically Aligned One-Dimensional Nanostructures for Alkaline Membrane Fuel Cells

An ionomer-free electrode containing vertically aligned one-dimensional nanostructures was designed and fabricated for anion exchange membrane fuel cells (AEMFCs) by hydrothermal and vapor deposition processes. The silver-coated zinc oxide (ZnO) nanorod arrays (diameter = ca. 100 nm) were directly aligned with the gas diffusion layer (GDL), and these one-dimensional structures of the electrode enhanced the mass transport of the reactants to the catalytic surface via its short diffusion pathway and ionomer-free nature. Applied as a cathode, the membrane electrode assembly (MEA) containing the vertically aligned gas diffusion electrode showed about 80% increased maximum power density than that of MEA containing a conventional electrode, which consisted of randomly dispersed carbon-supported nanoparticle catalysts and an ionomer. Moreover, the durability test revealed that the prepared ionomer-free catalyst layer was a more stable electrode than the conventional one. Also, water consumption and oxygen transport characteristics of AEMFC with the ionomer-free electrode at the cathode were intensively investigated by varying the electrode thickness and compositions. (C) 2021 The Electrochemical Society ("ECS"). Published on behalf of ECS by IOP Publishing Limited.11Nsciescopu

Design Rule for Constructing Buckling-Free Polymeric Stencil with Microdot Apertures

A polymeric stencil with microdot apertures made by using polydimethylsiloxane (PDMS) molds with pillar patterns has many advantages, including conformal contact, easy processability, flexibility, and low cost compared to conventional silicon-based membranes. However, due to the inherent deformability of PDMS materials in response to external pressure, it is challenging to construct structurally stable stencils with high structural fidelity. Here, we propose a design rule on the buckling pressure for constructing polymeric stencils without process failure. To investigate the critical buckling pressure (Pcr), stencils are fabricated by using different PDMS molds with aspect ratio variations (AR: 1.6, 2.0, 4.0, and 5.3). By observing the buckled morphology of apertures, the structures can be classified into two groups: low (AR 1.6 and 2.0) and high (AR 4.0 and 5.3) AR groups, and Pcr decreases as AR increases in each group. To investigate the results theoretically, the analysis based on Euler&rsquo;s buckling theory and slenderness ratio is conducted, indicating that the theory is only valid for the high-AR group herein. Besides, considering the correction factor, Pcr agrees well with the experimental results

Moth-eye Structured Polydimethylsiloxane Films for High-Efficiency Perovskite Solar Cells

Highlights Moth-eye structured polydimethylsiloxane (PDMS) films with different sizes were fabricated to improve the efficiency of perovskite solar cells. The PDMS with 300-nm moth-eye films significantly reduced light reflection at the front of the glass and therefore enhanced the solar cell efficiency of ~ 21%. The PDMS with 1000-nm moth-eye films exhibited beautiful coloration.Large-area polydimethylsiloxane (PDMS) films with variably sized moth-eye structures were fabricated to improve the efficiency of perovskite solar cells. An approach that incorporated photolithography, bilayer PDMS deposition and replication was used in the fabrication process. By simply attaching the moth-eye PDMS films to the transparent substrates of perovskite solar cells, the optical properties of the devices could be tuned by changing the size of the moth-eye structures. The device with 300-nm moth-eye PDMS films greatly enhanced power conversion efficiency of ~ 21% due to the antireflective effect of the moth-eye structure. Furthermore, beautiful coloration was observed on the 1000-nm moth-eye PDMS films through optical interference caused by the diffraction grating effect. Our results imply that moth-eye PDMS films can greatly enhance the efficiency of perovskite solar cells and building-integrated photovoltaics.EMP_ID:A004761DEPT_NM:기계항공공학부EMAIL:[email protected]

Multiscale Hierarchical Patterning by Sacrificial Layer-Assisted Creep Lithography

The capability to fabricate various multiscale structures without limitations of size, morphology, and number of hierarchies via a simple process is highly desired in modern research. This work reports a powerful multiscale-patterning method called sacrificial layer-assisted creep lithography (SCL). Multiscale structures are successfully obtained by introducing a sacrificial layer, which has low creep compliance and preferential solubility in a nonpolar solvent, on a Nafion film during an additional creep-based imprinting process. Through this method, deformation or geometrical loss of preformed structures and complex multiscale structures could be prevented including three-level structures that are successfully constructed with well-preserved nano/microstructures thanks to the sacrificial layer. To assess the diverse applicability of the SCL, a multiscale poly(dimethylsiloxane) channel with vertically crossed two-groove structures is fabricated, and the directional switching of droplet spreading depending on the direction of the applied strain is demonstrated with the structure. Further, using multiscale pyramid structures, the overlapped optical properties of nano- and microstructures, which enhance overall reflectance of the surface, are verified.N

Guided cracking of electrodes by stretching prism-patterned membrane electrode assemblies for high-performance fuel cells

Guided cracks were successfully generated in an electrode using the concentrated surface stress of a prism-patterned Nafion membrane. An electrode with guided cracks was formed by stretching the catalyst-coated Nafion membrane. The morphological features of the stretched membrane electrode assembly (MEA) were investigated with respect to variation in the prism pattern dimension (prism pitches of 20 μm and 50 μm) and applied strain (S ≈ 0.5 and 1.0). The behaviour of water on the surface of the cracked electrode was examined using environmental scanning electron microscopy. Guided cracks in the electrode layer were shown to be efficient water reservoirs and liquid water passages. The MEAs with and without guided cracks were incorporated into fuel cells, and electrochemical measurements were conducted. As expected, all MEAs with guided cracks exhibited better performance than conventional MEAs, mainly because of the improved water transport. © 2018 The Author(s)1