Three-dimensional, ordered macroporous materials such as inverse opal structures are attractive materials for various applications in electrochemical devices because of the benefits derived from their periodic structures: relatively large surface areas, large voidage, low tortuosity and interconnected macropores. However, a direct application of an inverse opal structure in membrane electrode assemblies has been considered impractical because of the limitations in fabrication routes including an unsuitable substrate. Here we report the demonstration of a single cell that maintains an inverse opal structure entirely within a membrane electrode assembly. Compared with the conventional catalyst slurry, an ink-based assembly, this modified assembly has a robust and integrated configuration of catalyst layers; therefore, the loss of catalyst particles can be minimized. Furthermore, the inverse-opalstructure electrode maintains an effective porosity, an enhanced performance, as well as an improved mass transfer and more effective water management, owing to its morphological advantages.

The production of multiscale architectures is of significant interest in materials science, and the integration of those structures could provide a breakthrough for various applications. Here we report a simple yet versatile strategy that allows for the LEGO-like integrations of microscale membranes by quantitatively controlling the oxygen inhibition effects of ultraviolet-curable materials, leading to multilevel multiscale architectures. The spatial control of oxygen concentration induces different curing contrasts in a resin allowing the selective imprinting and bonding at different sides of a membrane, which enables LEGO-like integration together with the multiscale pattern formation. Utilizing the method, the multilevel multiscale Nafion membranes are prepared and applied to polymer electrolyte membrane fuel cell. Our multiscale membrane fuel cell demonstrates significant enhancement of performance while ensuring mechanical robustness. The performance enhancement is caused by the combined effect of the decrease of membrane resistance and the increase of the electrochemical active surface area.

Heteroatom‐doped porous carbon materials have attracted much attention because of their extensive application in energy conversion and storage devices. Because the performance of fuel cells and the rate capability of supercapacitors depend significantly on multiple factors, such as electrical conductivity and transport rate of ions and reactants, designing these carbon‐based materials to optimize performance factors is vital. In order to address these issues, alveoli that possess a hollow cavity where oxygen exchange can occur are synthesized, inspired by N‐doped carbon materials with a high surface area and low transport resistance. By incorporating a dopamine coating on zeolitic imidazolate framework (ZIF), pore size is modified and electrical conducting pathways are constructed, resulting in changes to the reaction kinetics. These highly interconnected electron connection channels and proper pore sizes facilitate the diffusion of reactants and the conduction of electrons, leading to high activity of the oxygen reduction reaction (ORR), which is comparable to Pt, and high rate performance in supercapacitors.

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.

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We investigated the carbon support microporosity effect on active site formation for the oxygen reduction reaction in Fe–N–C catalysts.

In spite of their high conversion efficiency and no emission of greenhouse gases, polymer electrolyte membrane fuel cells (PEMFCs) suffer from prohibitively high cost and insufficient life-span of their core component system, the membrane electrode assembly (MEA). In this paper, we are proposing Ti foam as a promising alternative electrode material in the MEA. Indeed, it showed a current density of 462 mA cm(-2), being ca. 166% higher than that with the baseline Toray 060 gas diffusion layer (GDL) (278 mA cm(-2)) with 200 ccm oxygen supply at 0.7 V, when used as the anode GDL, because of its unique three-dimensional strut structure promoting highly efficient catalytic reactions. Furthermore, it exhibits superior corrosion resistance with almost no thickness and weight changes in the accelerated corrosion test, as opposed to considerable reductions in the weight and thickness of the conventional GDL. We believe that this paper suggests profound implications in the commercialization of PEMFCs, because the metallic Ti foam provides a longer-term reliability and chemical stability, which can reduce the loss of Pt catalyst and, hence, the cost of PEMFCs.

Ionic resistance and double layer capacitance of catalyst layer (CL) variations with the thickness of the cathode CL were estimated by electrochemical impedance spectroscopy (EIS) using the modified transmission-line model (TLM). 0.1–0.4 mgPt cm−2 of commercial 20, 40, and 60 wt% Pt/C catalysts were used to control cathode CL thicknesses. The catalyst with a low Pt to C ratio was favorable for maximum power density when the catalyst loaded was ≤0.2 mgPt cm−2, and the catalyst with a high Pt to C ratio was favorable when catalyst loading was ≥0.3 mgPt cm−2. The electrochemical surface areas of 20, 40, and 60 wt% Pt/C were different, whereas the Pt utilization of these catalysts was similar. Modified TLM under the non-faradaic condition was used for an easy estimate of the ionic resistance and double layer capacitance of the CL. Moreover cell inductance, electrolyte resistance, and the charge transfer resistance of crossovered H2 were used for a precise estimate. The ionic resistances and double layer capacitances of the CL were linearly proportional to CL thickness regardless of the Pt to C ratio.