Facile Multiscale Patterning by Creep-Assisted Sequential Imprinting and Fuel Cell Application

Abstract

The capability of fabricating multiscale structures with desired morphology and incorporating them into engineering applications is key to realizing technological breakthroughs by employing the benefits from both microscale and nanoscale morphology simultaneously. Here, we developed a facile patterning method to fabricate multiscale hierarchical structures by a novel approach called creep-assisted sequential imprinting. In this work, nanopatterning was first carried out by thermal imprint lithography above the glass transition temperature (Tg) of a polymer film, and then followed by creep-assisted imprinting with micropatterns based on the mechanical deformation of the polymer film under the relatively long-term exposure to mechanical stress at temperatures below the Tg of the polymer. The fabricated multiscale arrays exhibited excellent pattern uniformity over large areas. To demonstrate the usage of multiscale architectures, we incorporated the multiscale Nafion films into polymer electrolyte membrane fuel cell, and this device showed more than 10% higher performance than the conventional one. The enhancement was attributed to the decrease in mass transport resistance because of unique cone-shape morphology by creep-recovery effects and the increase in interfacial surface area between Nafion film and electrocatalyst layer.

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

“…To further confirm the degree of mass transfer at the cathode catalyst, we calculated the oxygen gain (Δ V ) using the following equation 14 , 28 : …”

“…Although many technological advances have been achieved in the research field of PEMFCs, some practical issues still hinder their commercialization. To obtain high device performance, ohmic loss should be reduced by using a thinned electrolyte membrane 8 – 10 and water transport at the cathode of the membrane electrode assembly (MEA) should be enhanced 11 – 14 . In relation to water transport, water molecules that are generated by the oxygen reduction reaction block the catalyst surface and pores in the cathode catalyst layer, reducing device performance.…”

Multifunctional Structured Platforms: From Patterning of Polymer-Based Films to Their Subsequent Filling with Various Nanomaterials

“…NIL has been widely utilized by many research groups for its high reproducibility in the realization of defect-free patterns over a large area [92] to be incorporated in sensors [93], organic solar cells [94], reverse osmosis membranes [95], and soft electrodes [96], or to develop applications in the biomedical field [97][98][99]. With NIL, different complex patterns such as elliptical hemisphere arrays [100], hole arrays [101], pillar structures [102,103], and nanogratings [104] can be achieved. Moreover, imprint molds [105] of different types have been designed, developed, and eventually improved in order to replicate high-resolution periodic patterns on various substrates with the help of various lithographic approaches derived from NIL that include thermal NIL, UV-based NIL, or molding capillaries NIL.…”

Synergetic Structural Transformation of Pt Electrocatalyst into Advanced 3D Architectures for Hydrogen Fuel Cells

“…Moreover, to lower the contact resistance at the electrode–electrolyte interface, some strategies for creating micro‐ or nanoscale patterns in polymer electrolytes have been reported. [ 182–184 ] Such approaches can be applied to both 3D Pt thin‐film electrodes and carbon‐supported Pt electrodes. For example, a multiscale‐patterned Nafion membrane for fuel cells was prepared using multiplex lithography, which showed a lower contact resistance at the electrode–electrolyte interface due to the increase in the membrane surface area (Figure 8g,h).…”