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The catalyst layer (CL) is a critical component that determines the performance of proton exchange membrane fuel cells, and the production process of CL is important issue. A CL is fabricated from a catalyst ink mixed with platinum-supported carbon (Pt/C), ionomer solution, and a solvent. When the catalyst ink is coated on the sheet and dried, the CL is formed. By transferring the CL to the membrane, catalyst coated membrane can be made [1]. The process from the initial characteristics of the catalyst ink to the drying process determines the structure of CL and dominates the characteristics of the fuel cell. Thus, quality control of the catalyst ink is important to form a high performance and uniform CL [2]. We have reported that alcohol oxidation reaction and condensation reaction, as catalyzed by platinum, occurred in the catalyst ink fabrication process [3]. Several reaction products, aldehydes, acids, and esters, were detected by gas chromatography mass spectrometry (GC/MS) [4]. In this study, concentration of those reaction products were measured quantitatively, and the effect of those reaction products on the catalyst ink property and CL quality was investigated. Catalyst ink was prepared by using the mixture of water and ethanol as a dispersant. We used platinum catalyst supported on carbon black and Nafion dispersion. The solvent was composed of ethanol and water. The weight ratio between ethanol and water was set to 46:54 or 60:40. Nonvolatile content was 10 wt%. Weight ratio between Nafion and the carbon support was 0.75. As a mixing process, a high-speed rotary type mixer was used, and mixing time was set to 10 min. The quantitative concentration of reaction products in each ink were analyzed by GC/MS. After concentration measurement, CL was fabricated using each ink. The crack formation was observed, and the correlation with the initial composition of the ink and the concentration of the reaction product was investigated. As a result of GC/MS, several reaction products (acetaldehyde, acetic acid, and ethyl acetate) were detected in the catalyst ink. Table 1 shows quantitative concentration of reaction products. Comparing the both catalyst inks, the concentration of acetaldehyde increased remarkably when the ethanol concentration increased. CLs were fabricated with using those catalyst inks and observed by microscope (Figure 1). There was no crack in the low ethanol concentration ink, and cracks occurred in the high ethanol concentration ink. Those results suggest that acetaldehyde may be a factor in causing cracks in the CL. To clarify the effect of acetaldehyde, acetic acid, and ethyl acetate on the crack formation in the CL, each substance was artificially added to the low ethanol concentration catalyst ink. In actual catalyst ink, it is considered that ethanol reacts to produce a reaction product. Therefore, in the modified catalyst ink, the amount of ethanol was reduced according to the amount of added substance. The CL was fabricated by using those catalyst ink and the observation results were shown in Figure 2. When the same amount of acetaldehyde contained in the high ethanol concentration catalyst ink was added, many cracks were generated in the CL. Several cracks occurred when ethyl acetate was added, but the required amount was significantly higher than the ethyl acetate concentration detected in the actual catalyst ink. No cracks were generated even if a large amount of acetic acid was added to the catalyst ink. These results indicate that the acetaldehyde is a factor of crack in the CL. It is considered that when the generated acetaldehyde exceeds a certain concentration in the catalyst ink, crack is caused in the CL. Acknowledgment: This study is based on the results obtained from a project commissioned by the New Energy and Industrial Technology Development Organization (NEDO). References: T. Suzuki, ECS Transactions, 75(14), 423-434 (2016). S.J. Shin et al., J. Power Source 106, 146-152 (2002). S. Uemura et al., J. Electrochem. Soc., 166-2, F89 (2019). S. Uemura et al., ECS Trans., 92-8, 183-187 (2019). Figure 1

Catalyst ink is a key material of the catalyst layer in a proton exchange membrane fuel cell, but can be degraded as the reactions of alcohols are promoted by Pt in the ink. The present study quantitatively determined the concentrations of reaction products in an ethanol/water-based catalyst ink, and the effects of these substances on the ink and catalyst layer were investigated. The acetaldehyde concentration was found to be the key factor, as acetaldehyde caused particle agglomeration in the catalyst ink and micro-scale crack formation in the catalyst layer.

The catalyst layer (CL) of polymer electrolyte fuel cell (PEFC) comprises catalyst particles, catalyst support (e.g., carbon particles), and proton-conductive ionomers. The CL plays a critical role in PEFC operation, and also the production process of CL is of significant importance in terms of the cell performance as well as the system cost. The decal method has been used in the commercial production of CL in membrane electrode assemblies, in which the catalyst ink is prepared by mixing catalyst particles and ionomer in the solvent, coated on a decal substrate, dried to form a particulate layer with a specified thickness, and transferred to a membrane via hot pressing [1,2]. Since the three-phase interface (catalyst-void-ionomer) is essential for the mass transport during the electrochemical reaction, it is desirable to control the microstructure of CL [3]. Therefore, the catalyst ink and its use in the decal process should be studied in detail. We have developed a novel approach to investigate the characteristics of catalyst ink by using magnetic resonance imaging (MRI) combined with nuclear magnetic resonance (NMR) spectroscopy [4]. Although traditional NMR studies of ionomers have been reported [5,6], the detailed discussion regarding the spatial inhomogeneity of particles in catalyst ink and their dynamics during the drying process has been lacking. MRI enables us to visualize the spatial variations in the sample characteristics which cannot be accessed through other spectroscopy techniques [7]. In this study, we applied MRI and 1H/19F NMR to the catalyst ink for the decal process for gaining an insight on the dispersion state of catalyst and ionomer. Using the mixture of water and NPA as a dispersant, we prepared catalyst ink samples. We used platinum catalyst supported on carbon black (Pt/C) and Nafion dispersion D2020 (Chemours). Pre-mixing of catalyst ink was performed using ultrasonicaton to break large Pt/C agglomerates into smaller units. We then used a thin-film spin system high-speed mixer Filmix (Primix), which is designed for the production of slurries of nanometer-sized particles, in the main mixing process. Because Nafion works as a dispersant of Pt/C particles, the dispersion state of Nafion has an impact on the dispersibility of the Pt/C particles and eventually on the stability of catalyst ink. We conducted MRI/NMR measurements for the catalyst ink samples at each stage of preparation process to investigate changes in the dispersion state of Pt/C particles and Nafion. We found a fully-mixed sample exhibited a MRI image with submillimeter fine contrast because air bubbles were mixed in the sample during the main mixing process. It was difficult to remove air bubbles from the sample only by leaving it at rest for several hours. This observation was supported by the rheology measurement of catalyst ink. Hence we needed to use a magnetic stirrer to effectively perform the degassing of catalyst ink after the main mixing process. The degassed state of catalyst ink was confirmed by MRI image and 1H NMR spectrum. 19F NMR spectra showed remarkable changes concerning the peaks associated with the main and side chains of Nafion, which indicated the dispersion state of Nafion varied during the mixing process. In the present work, we have demonstrated that our experimental approach can provide a unique capability to investigate the dispersion state of catalyst ink. It is expected that the catalyst ink and its drying process will be investigated to optimize the fabrication process of PEFC catalyst layer. Acknowledgment:This study is based on the results obtained from a project commissioned by the New Energy and Industrial Technology Development Organization (NEDO). References:[1] H.J. Cho et al., Int. J. Hydrogen Energy 36 (2011) 12465. [2] X. Liang et al., Fuel 139 (2015) 393. [3] N. Zamel, J. Power Sources 309 (2016) 141. [4] Y. Kameya et al., ECS Trans 75 (2016) 275. [5] S. Ma et al., Solid State Ionics 178 (2007) 1568. [6] C. Welch et al., ACS Macro Lett. 1 (2012) 1403. [7] M.H. Levitt, "Spin dynamics" 2nd edition, Wiley (2008).

Perfluorosulfonated ionomers are the most successful ion-exchange membranes at an industrial scale. One recent, cutting-edge application of perfluorosulfonated ionomers is in polymer electrolyte fuel cells (PEFCs). In PEFCs, the ionomers are used as a component of the catalyst layer (CL) in addition to functioning as a proton-exchange membrane. In this study, the microstructures in the CLs of PEFCs were characterized by combined synchrotron X-ray scattering and transmission electron microscopy (TEM) analyses. The CL comprised a catalyst, a support, and an ionomer. Fractal dimensional analysis of the combined ultrasmall- and small-angle X-ray scattering profiles indicated that the carbon-black-supported Pt catalyst (Pt/CB) surface was covered with the ionomer in the CL. Anomalous X-ray scattering revealed that the Pt catalyst nanoparticles on the carbon surfaces were aggregated in the CLs. These findings are consistent with the ionomer/catalyst microstructures and ionomer coverage on the Pt/CB surface obtained from TEM observations.

Crystals of salt monomer prepared from aromatic tetracarboxylic acids and aromatic diamines were polymerized at 220°C for 3 h and at 400°C for 3 h under argon flow. Highly crystalline polyimide particles having clear morphology were obtained with good yield. They were lozenge-like crystals, long plate-like crystals, fibrillar crystals, and spherical aggregates of plate-like crystals. The crystals of salt monomer were polymerized in the solid-state with maintaining the morphology, and therefore the morphology of the polyimide particles were the same to that of the crystals of the corresponding salt monomer. Molecular orientation in the lozenge-shaped crystal of poly( p-phenylene pyromelliteimide) was examined by selected area electron diffraction, and the polymer molecules aligned perpendicular to the plate plane which was the direction of the thickness. Obtained particles possessed good thermal stability.

We demonstrated the controlled incorporation of Au nanoparticle grafted with polystyrene (PS) molecules in the helical microdomains of ABC-type linear triblock terpolymers composed of PS, polyisoprene (PI) and poly(methyl methacrylate) (PMMA). The Au nanoparticles grafted with three PSs with different molecular weights were synthesized and incorporated into the terpolymer films. The morphologies of composite films and localization of Au nanoparticles were three-dimensionally characterized with transmission electron microtomography observation. By varying the molecular weights of grafted PS molecules on Au nanoparticles, their assemblies were successfully controlled in the double-helical microdomains.

Metal phthalocyanines (PCs) are promising materials for various applications, including pigments, color filters, photovoltaic devices, and nonlinear optics, owing to their specific light-absorption properties and high stability to chemical and thermal degradation. Nanocrystals (NCs) of metal PCs have received much attention because the optical and electronic properties of metal PCs are improved considerably by decreasing the crystal size to the nanoscale. In this study, we demonstrated the direct synthesis of Cu and Zn PCs in nanosized micelles by irradiating precursors with UV light. The synthesized metal PC NCs were stably dispersed in water by adding polyethylene glycol as a stabilizer. The aqueous dispersions of PC NCs showed strong visible light absorption from 500 to 800 nm and high transparency at wavelengths in the non-absorption region.

The epitaxial relationship in the thermal phase transition between double gyroid (DG) and hexagonally packed cylinder (HEX) phases in polystyrene-block-polyisoprene thin films on Si wafer was investigated using transmission electron microtomography and grazing incidence small-angle X-ray scattering. Two different types of epitaxial transitions were observed, and they appeared to be selectively favored depending on the transition direction. One type of epitaxial relationship prevails in the phase transition from DG to HEX upon heating in which {121}DG, {111}DG, and {220}DG are converted to {100}HEX, {110}HEX, and {001}HEX, respectively. The interphase planes are {220}DG and {001}HEX, and the cylinders meet the {220}DG plane perpendicularly (head-on, Type A) at the grain boundary between DG and HEX. Although there are small dimensional mismatch and distortion in the location of the cylinders in this epitaxial relationship, all cylinders are formed along the topologically equivalent DG skeletal path. On the ...

The control of microphase-separated structures in a poly(styrene-block-butadiene-block-methyl methacrylate) (SBM) was investigated in three dimensions by transmission electron microtomography. Neat SBM self-assembled into a double-helical structure of polybutadiene (PB) domains around hexagonally packed core polystyrene (PS) cylinders in a poly(methyl methacrylate) matrix. When PS homopolymer with a lower molecular weight than that of the PS block in SBM was added to the SBM, the PB domains transformed from double-helical structures to spherical domains, while maintaining the helical trajectories. In contrast, adding a higher molecular weight PS to the SBM changed the helical structures from double- to triple-stranded structures and even to four-stranded structures. The helical structures of the PB domains were strongly affected by the distribution of the blended polystyrenes in the core cylindrical PS domains.

We report on the formation of tetragonally perforated lamellae from a polybutadiene-block-poly(2-vinylpyridine)-block-poly(tert-butyl methacrylate) (BVT) triblock terpolymer, PB22P2VP29PtBMA49110, ...

The orientation of nanoscale double-helical morphologies of SBM triblock terpolymer at various film thicknesses (h) were studied using transmission electron microtomography, following solvent annealing and drying at a controlled solvent evaporation rate (R). The combination of h and R were found to be essential factors to determine orientation of the double-helical microdomains in thin films. Perpendicularly aligned double-helical morphology extending several micrometers from the substrate to the air surface was achieved.

The effect of preferential wetting of one of the constituent block chains and corresponding block copolymer morphologies to a carbon substrate is studied from a molecular level. The single chain distribution of the block copolymer was estimated as a function of the distance from the substrate by a combined method of transmission electron microtomography (TEMT) and self-consistent field (SCF) simulation. The former provides three-dimensional (3D) morphological information of cylindrical microdomains near the surface, while the latter utilizes the 3D morphology to quantitatively determine the interaction between the block chains and substrate, which is further used to estimate the single chain distribution of one of the block chains, i.e., the subchain, of the matrix. It was found that the subchains in the vicinity of the wetting layer are substantially compressed, while the radius of gyration of the subchain at a distance L (L is the interlayer distance of the cylindrical microdomains from the substrate) has already reached the same value as that in the bulk, indicating that the propagation of the surface interaction is limited to one layer. The methodology developed in this study can be used not only to estimate the surface effect on polymer chains for a variety of different surfaces, but also to provide a means to understand complicated block copolymer morphologies from a molecular level.

Block copolymer nanopaticles were prepared from the mixture solutions containing good/poor solvents by a simple evaporation process. The block copolymers formed disorder, unidirectionally stacked lamellar, and onion-like structures in nanoparticles depending on preparation temperatures. Thermal annealing induced the disorder-order phase transition and order-order phase transformation in the block copolymer nanoparticles, even though the annealing temperature is lower than the of one polymer segment. The unusual thermal behaviors suggest that the glass transition temperature of the block copolymer is decreased by the effect of nanoparticle, whose surface areas are larger than their volumes.

Polymer electrolyte fuel cells (PEFCs) are attractive power converters for various applications including electric vehicles and stationary powers without emitting CO2. The electrochemical reaction to generate electric power occurs at the interface of catalyst nanoparticle and ionomer in a catalyst layer on electrodes. The catalyst layers consist of Pt catalyst nanoparticles supported on carbon (Pt/C) and ionomer as the binder. The fine structure of the catalyst layer such as the connected structure of carbon support, and the interconnected pore structure, and the state of ionomer coverage on carbon support, governs the performance of PEFCs. The catalyst layer is fabricated by coating of the catalyst ink consisting of the Pt/C, ionomer, and solvents. Precise structural analyses of the catalyst ink and the catalyst layer have been reported. However, the determining factor for the catalyst layer formation is still unclear. In this study, we performed in situ grazing-incidence small-angle x-ray scattering (GISAXS) measurements to investigate the aggregation process of Pt/C during the drying process of the catalyst ink. The catalyst ink was prepared by blending Pt/C (TEC10E50E, Tanaka Kikinzoku Kogyo), ionomer (Nafion® dispersion, DE2020, Chemours) and mixture of water/1-propanol (NPA) (1/1 v/v) at 6.5/3.5/90 w/w/w. The weight ratio of ionomer to carbon was 1:1. The catalyst ink was coated on a Si wafer using an automatic film applicator at 25 °C. The stainless-steel applicator with a gap of 100 μm height and 40 mm width was used as the blade. The drawing speed was fixed at 20 mm s-1 for all coatings. In situ GISAXS measurements were carried out at the BL45XU beam line of SPring-8. The X-ray with 0.100 nm in wavelength impinged onto the coating film under an incident angle of 0.12° and the scattering data were collected with 2D detector (PILATUS3X 2M Dectris Ltd.) located at a distance of 3.5 m from the sample. Figure 1a and 1b show 2D GISAXS patterns collected at several elapsed times (t), and the scattering intensities obtained from vertical line cuts of 2D patterns at qy = 7.37×10−2 nm−1 in a width of Δqy = 6.13×10−2 and plotted against qz , respectively. As seen in Figure 1b, the intensity profile at t = 70 s includes a maximum at qz = 0.2 nm−1, which shifts toward smaller qz with increasing t from 70 s to 250 s. It suggests that 30-nm-sized Pt/C primary particles aggregate to increase the size and spacing with the solvents evaporate. With further increasing t, the intensity profile did not change, indicating that the nanoscale structure was fixed at t = 250 s. In contrast, the gravimetry for the same process indicates that the decrease of the catalyst ink weight due to solvents evaporation completes at t = 1600 s. These results show that the aggregation of Pt/C particles mostly completes in the first half of drying process This work was supported by the PEMFC Research and Development Program for “Highly-Coupled Analysis of Phenomena in MEA and its Constituents and Evaluation of Cell Performance” from the New Energy and Industrial Technology Development Organization, NEDO, Japan. The synchrotron radiation experiments were performed at BL45XU beam line in SPring-8 with the approval of JASRI (Proposal No. 2017A1002 and 2017B1006). Figure 1

Microphase-separated structures in poly(styrene-block-isoprene) (SI) block copolymer thin films were investigated by transmission electron microtomography (TEMT). The SI block copolymer showed cylindrical microdomains in the bulk state. Several block copolymer thin films with different thicknesses were prepared by spin-coating and were extensively annealed before the TEMT experiments. Intriguingly, although the cylindrical morphology orienting parallel to the substrate was observed in most of the cases, spherical microdomains were found at certain film thicknesses. The thickness dependence was investigated using a computer simulation based on the self-consistent-field theory, producing a morphological phase diagram based on minimizing free energy. We find that the distortion of the hexagonal lattice of the cylindrical microdomains caused the morphological transition to the spherical microdomains.

Transmission electron microtomography (TEMT) has proven to be useful for investigating three-dimensional (3D) nanostructures in polymeric systems. However, the conventional TEMT that uses a tilt series around an axis occasionally fails to reconstruct nanostructures, especially when the nanostructure is highly anisotropic. Namely, if a certain geometrical relationship between orientation of the nanostructure and the tilt axis is fulfilled, the nanostructure does not appear in the 3D reconstruction. This problem can be solved by tilting the specimen around two (orthogonal) tilt axes and combining the resulting two 3D reconstructions after precise alignment between them. The strategy, called “dual-axis tomography”, is used to observe one of the commonly observed anisotropic polymer nanostructures, cylindrical morphology, of poly(styrene-block-isoprene) block copolymer. It was experimentally observed that the cylindrical nanodomains that were “missing” in one of the two tomograms were complementary reconstruc...

The catalyst layer (CL) of polymer electrolyte fuel cell (PEFC) comprises catalyst particles, catalyst support (e.g., carbon particles), and proton-conductive ionomers. The CL plays a critical role in PEFC operation, and also the production process of CL is of significant importance in terms of the cell performance as well as the system cost. The decal method has been used in the commercial production of CL in membrane electrode assemblies, in which the catalyst ink is prepared by mixing catalyst particles and ionomer in the solvent, coated on a decal substrate, dried to form a particulate layer with a specified thickness, and transferred to a membrane via hot pressing [1,2]. Since the three-phase interface (catalyst-void-ionomer) is essential for the mass transport during the electrochemical reaction, it is desirable to control the microstructure of CL [3]. Therefore, the catalyst ink and its use in the decal process should be studied in detail. We have developed a novel approach to investigate the characteristics of catalyst ink by using magnetic resonance imaging (MRI) combined with nuclear magnetic resonance (NMR) spectroscopy [4]. Although traditional NMR studies of ionomers have been reported [5,6], the detailed discussion regarding the spatial inhomogeneity of particles in catalyst ink and their dynamics during the drying process has been lacking. MRI enables us to visualize the spatial variations in the sample characteristics which cannot be accessed through other spectroscopy techniques [7]. In this study, we applied MRI and 1H/19F NMR to the catalyst ink for the decal process for gaining an insight on the dispersion state of catalyst and ionomer. Using the mixture of water and NPA as a dispersant, we prepared catalyst ink samples. We used platinum catalyst supported on carbon black (Pt/C) and Nafion dispersion D2020 (Chemours). Pre-mixing of catalyst ink was performed using ultrasonicaton to break large Pt/C agglomerates into smaller units. We then used a thin-film spin system high-speed mixer Filmix (Primix), which is designed for the production of slurries of nanometer-sized particles, in the main mixing process. Because Nafion works as a dispersant of Pt/C particles, the dispersion state of Nafion has an impact on the dispersibility of the Pt/C particles and eventually on the stability of catalyst ink. We conducted MRI/NMR measurements for the catalyst ink samples at each stage of preparation process to investigate changes in the dispersion state of Pt/C particles and Nafion. We found a fully-mixed sample exhibited a MRI image with submillimeter fine contrast because air bubbles were mixed in the sample during the main mixing process. It was difficult to remove air bubbles from the sample only by leaving it at rest for several hours. This observation was supported by the rheology measurement of catalyst ink. Hence we needed to use a magnetic stirrer to effectively perform the degassing of catalyst ink after the main mixing process. The degassed state of catalyst ink was confirmed by MRI image and 1H NMR spectrum. 19F NMR spectra showed remarkable changes concerning the peaks associated with the main and side chains of Nafion, which indicated the dispersion state of Nafion varied during the mixing process. In the present work, we have demonstrated that our experimental approach can provide a unique capability to investigate the dispersion state of catalyst ink. It is expected that the catalyst ink and its drying process will be investigated to optimize the fabrication process of PEFC catalyst layer. Acknowledgment: This study is based on the results obtained from a project commissioned by the New Energy and Industrial Technology Development Organization (NEDO). References: [1] H.J. Cho et al., Int. J. Hydrogen Energy 36 (2011) 12465. [2] X. Liang et al., Fuel 139 (2015) 393. [3] N. Zamel, J. Power Sources 309 (2016) 141. [4] Y. Kameya et al., ECS Trans 75 (2016) 275. [5] S. Ma et al., Solid State Ionics 178 (2007) 1568. [6] C. Welch et al., ACS Macro Lett. 1 (2012) 1403. [7] M.H. Levitt, “Spin dynamics” 2nd edition, Wiley (2008).

Polymer electrolyte fuel cells (PEFCs) have recently received considerable attention as a next-generation power source, since from the practical viewpoints of energy efficiency and environmental friendliness, they compare favorably with present energy sources1. The catalyst layer (CL) of membrane electrode assembly (MEA) in the PEFC consists from the carbon supported platinum (Pt) nanoparticle and ionomer. The CL is fabricated by coating of the catalyst ink containing the platinum-loaded carbon (Pt/C) catalyst, ionomer, and solvents. The electrochemical activity and transport phenomena in a MEA are affected by the nanostructures in the CL2,3. Though many research activities have been reported on a structural formation in the CL4,5, the dynamics of the CL formation process during the solvent evaporation is still unclear. In this study, we have demonstrated that the structural evolution in the catalyst inks and CLs in drying process was elucidated by cryogenic scanning electron microscopy (cryo-SEM) and cryogenic transmission electron microscopy (cryo-TEM). The catalyst ink was prepared by blending a Pt/C catalyst, ionomer (Nafion®) and solvents (water/1-propranol (NPA) =1:1 in volume ratio). The solid content of the catalyst ink was 10 wt.%, and the weight ratio of ionomer to carbon ratio was 1.0. The catalyst ink was frozen using a high-pressure freezer (EM ICE, Leica Microsystems, Vienna, Austria). The block surface of the frozen catalyst ink for the cryo-SEM observation was then trimmed with a cryo ultramicrotome (EM UC7/FC7T, Leica Microsystems, Vienna, Austria). The CLs were prepared by following procedure. The catalyst ink was coated on Cu substrates (3 mm diameter) placed on a PTFE film using a film applicator. The Cu substrates coated catalyst ink were picked up in 60 and 180 sec after the coating, and soaked into liquid ethane for freezing (CL60 and CL180, respectively). The dried CL was prepared by drying over an hour at room temperature (CLdry). The frozen catalyst ink and catalyst layers on the Cu substrates were observed with a scanning electron microscope (JSM-6701F, JEOL, Tokyo, Japan) incorporated with a liquid nitrogen cooled-stage (EM VCT100, Leica Microsystems, Vienna, Austria). The cryo-SEM image of the catalyst ink is shown in Fig. 1(a). The brighter particle and darker region correspond to the Pt catalyst nanoparticles and the frozen solvents, respectively. The Pt/C particles formed the several hundred nanometers to micrometer size agglomerates in the catalyst ink. The cryo-SEM images of the surface structure on the CL60 and CL180 are shown in Fig. 1(b) and (c), respectively. The bright particles with several-hundred nanometers correspond to the frost on the sample surface. In CL60, the shape of sample surface of the CL was flat and the agglomerates of Pt/C particles observed in the catalyst ink could not be seen on the surface. In CL180, the several ten micrometers agglomerates of the Pt/C particles could be seen in the CL. In contrast, the solvents and ionomers exhibited the network structure, which connected between the Pt/C agglomerates. In CLdry, the network structure does not exist any longer as shown in Fig. 1(d). In the CL formation process, the size of agglomerated of the Pt/C particles grew to larger agglomerates induced by solvent evaporation. The structure of the CL was changed the liquid–like to the solid via the network structure. The submicron structural evolution in the CL formation process during the solvent evaporation is demonstrated by the cryo-SEM observations. The further nanostructural investigations of the catalyst ink and the CL using cryo-TEM are now in progress. Acknowledgment This presentation is based on results obtained from the PEMFC Research and Development Program for “Highly‐Coupled Analysis of Phenomena in MEA and its Constituents and Evaluation of Cell Performance” commissioned by the New Energy and Industrial Technology Development Organization (NEDO). References 1. Mehta, V. and Cooper, J. S. Journal of Power Sources 114, 32–53 (2003). 2. Holdcroft, S. Fuel Cell Catalyst Layers: A Polymer Science Perspective. Chem. Mater. 26, 381–393 (2014). 3. Takeshi Terao, Gen Inoue, Motoaki Kawase, Norio Kubo, Makoto Yamaguchi, Kouji Yokoyama, Tomomi Tokunaga, Kazuhiko Shinohara, Yuka Hara, and Toru Hara. Journal of Power Sources 347, 108–113 (2017). 4. Fan Xu, HangYu Zhang, Jan Ilavsky, Lia Stanciu, Derek Ho, Matthew J Justice, Horia I Petrache, and Jian Xie. Langmuir 26, 19199–19208 (2010). 5. Takahashi, S., Mashio, T., Horibe, N., Akizuki, K. and Ohma, A. ChemElectroChem 2, 1560–1567 (2015). Figure 1

Nafion has been well known as the standard perfluorosulfonated material in the field of Polymer Electrolyte Membrane Fuel Cell and has been irreplaceable materials as a membrane and an ionomer of catalyst layer. Many researchers have investigated the proton conduction, water-uptake, mechanical property and nano-structure1,2).As for nano-structure researches, small angle X-ray scattering and small angle neutron scattering revealed the morphology characterization of Nafion solution3). X-ray irradiates many molecules in Nafion solution.The characterization was attributed to average information.TEM is very useful apparatus to observe nano-structure of materials. It is applicable to samples which withstand a vacuum condition.Nafion solution is not able to be observed by TEM because of high vapor pressure of solution. Freeze method is an idea to measure Nafion solution. In case of freeze method using liquid nitrogen, vaporized nitrogen severely damaged the sample. In case of another freeze liquid ethane method Figure1, liquid ethane was cooled by liquid nitrogen to avoid vaporization of ethane.Figure 2 shows TEM photograph of Nafion solution. Objects of rod structure were observed, some rods seemed to be linked each other and dark points also observed. Rod structure with radius 1.2 to 3.6 nm and length 16nm was predicted when entangle molecular weight 54904), EW=1000 and Nafion molecular weight between 0.1million and 1million were applied.Rod structure of TEM photograph is interpreted as the prediction.Dark points of TEM Photograph might be nano-crystals of PTFE part of Nafion.SAXS measurement of Nafion solution also showed nanocrystal with interval of 18nm. This interval value fairly fits to distances between dark points. This presentation is based on results obtained from a project commissioned by the New Energy and Industrial Technology Development Organization (NEDO). References 1)Kenneth A. Mauritz and Robert B. Moore, “State of Understanding of Nafion”, Chem. Rev. 2004, 104, 4535-4585 2)Adam Z. Weber and John Newman,” Modeling Transport in Polymer-Electrolyte Fuel Cells”, Chem. Rev. 2004, 104, 4679-4726 3)Makoto Yamaguchi, Takuro Matsunaga, Kazuki Amemiya, Akihiro Ohira, Naoki Hasegawa, Kazuhiko Shinohara, Masaki Ando and Toshihiko Yoshida, “Dispersion of Rod-like Particles of Nafion in Salt-Free Water/1-Propanol and Water/Ethanol Solutions”, J. Phys. Chem. B 2014, 118, 14922-14928 4)Souheng Wu; “Characterization of Polymer Molecular Weight Distribution by Transient Viscoelasticity: Polytetrafluoroethylenes”, Polymer Engineering & Science, 1988 - Wiley Online Library Figure 1

Block copolymer nanopaticles were prepared from the mixture solutions containing good/poor solvents by a simple evaporation process. The block copolymers formed disorder, unidirectionally stacked lamellar, and onion-like structures in nanoparticles depending on preparation temperatures. Thermal annealing induced the disorder-order phase transition and order-order phase transformation in the block copolymer nanoparticles, even though the annealing temperature is lower than the of one polymer segment. The unusual thermal behaviors suggest that the glass transition temperature of the block copolymer is decreased by the effect of nanoparticle, whose surface areas are larger than their volumes.

The effect of confinement on microphase-separated structures of a diblock copolymer is investigated in nanoparticles serving as a three-dimensional (3D) confinement system. We succeeded in preparing nanoparticles having various types of complex structures from hydrophobic diblock copolymers by a simple solvent evaporation method. The detailed 3D structural analysis of the nanoparticles by transmission electron microtomography (TEMT) revealed that complex structures were found only to form in the nanoparticle surface region, the thickness of which corresponded to the single-molecule length of the block copolymer in the bulk state. These results indicate that 3D confinement fundamentally affects block copolymer self-assemblies most strongly in the surface region of nanoparticles but only weakly in the central region.

A 3-dimensional Fddd network structure of a polystyrene-block-polyisoprene (PS-b-PI) diblock copolymer (Mn = 31500, fPI = 0.645) was observed for the first time in real space by transmission electron microtomography (TEMT). In a 650 nm thick film of the PS-b-PI thin film on a silicon wafer, the Fddd phase was developed after annealing at 215 °C for 24 h. The single network structure consists of the connected tripodal units of minor PS block domains. The {111}Fddd plane, the densest plane of the minor PS phase, was found to orient parallel to the film plane. The transitional structure from the wetting layer at the free surface to the internal {111}Fddd plane via a perforated layer structure was also observed.

We have been developing new techniques to evaluate polymer nano-alloys and nano-composites. This nanotechnology can be classified into nano-three dimensional (3D) measurement, nano-physical properties evaluation systems, and nano-spectroscopy. As for the nano-3D measurement, we developed polymer oriented energy-filtered 3D transmission electron microscopy. With this method, we can access important 3D structural and elemental information that cannot be obtainable from ordinary TEM. Nano-physical properties evaluation systems were also established by developing atomic force microscopy force-distance curve measurement. The distribution of mechanical properties such as Young's modulus and adhesive energy was quantitatively obtained on high lateral resolution. These methods give new pieces of information unobtainable by the conventional techniques on polymer nanotechnology. Several results are shown here.

An order-order transition (OOT) from the bicontinuous double-gyroid (G) structure to the hexagonally-packed cylindrical (C) structure in a poly(styrene-block-isoprene) (SI) block copolymer was investigated by transmission electron microtomography (TEMT). The coexistence of the G and C microdomains during the OOT was observed. The boundary structures between the G and C microdomains were directly three-dimensionally visualized. It was found that the {220} plane of the G structure changed to the {110} plane of the newlygenerated C structure, consistent with Matsen’s prediction from his computer simulations based on self-consistent field (SCF) theory.

Polymer electrolyte membrane fuel cell (PEMFC) has been considered as a highly efficient electrochemical power converter with zero emissions of CO2. The oxygen reduction reaction (ORR) occurs at the interface between platinum (Pt) catalyst nanoparticle and ionomer in the catalyst layer of membrane electrode assembly (MEA). The catalyst layer is fabricated by coating of the catalyst ink containing the carbon-supported platinum (Pt/C) catalyst, ionomer, and solvents. In the catalyst layers, ionomer provided an ultra-thin film, coating the Pt catalyst nanoparticles and the carbon support surfaces. These ultra-thin films have a significant influence on the electrochemical activity and transport phenomena that determine the whole cell performances. Recently, precise structural analyses of catalyst inks and catalyst layers have been reported. To the best of our knowledge, however, the dynamics of the catalyst layer formation process remain unclear. Herein, we performed in-situmeasurements of synchrotron radiation grazing-incidence small-angle X-ray scattering (GISAXS) of a catalyst ink during drying process. The ink was coated on a silicone (Si) wafer with a film applicator and the scattering images of the film were acquired as a function of the elapsed time. The catalyst ink was prepared by blending a Pt/C catalyst, ionomer (Nafion®) and solvents (water/1-propanol (NPA) =1:1 in volume ratio). The solid content of the catalyst ink was 10 wt%, and the weight ratio of ionomer to carbon ratio was 1:1. The catalyst ink was coated on a Si wafer using a film applicator and X-ray beam (wavelength λ = 0.100 nm) was irradiated on the film at a small grazing angle (0.15 °) and the scattering images were measured using a photon counting detector (PILATUS3X 2M, DECTRIS Ltd.) at a distance of 2700 mm from the film (BL45XU/SPring-8). Selected 2D GISAXS patterns during catalyst layer formation process are shown in Fig. 1. The 2D GISAXS pattern significantly change with the elapsed time, in particular for the out-of-plane direction. Several scattering peaks appear immediately after the ink coating. With time elapsed, the peak intensities increase and their peak positions shift toward smaller qz . The intensity profiles on the out-of-plane q z axis of GISAXS patterns measured during catalyst layer formation process as a function of the elapsed time (t) are shown in Fig. 2. From t = 0 s, the peak at around q z ~ 0.2 nm−1 shift toward smaller q z with increasing t. Furthermore, at t ~ 50 s, two peaks around q z ~ 0.5 nm−1 appear and combine into one peak. Thereafter, this peak shifts toward smaller q z with increasing t. These results demonstrate that nanostructural evolution of catalyst layer formation process can be traced by utilizing synchrotron X-ray scattering. The peak shifts would be due to the growth of Pt/C agglomeration induced by solvent evaporation. For the precise assignment of scattering peaks, further investigations based on direct observations of the catalyst ink using cryogenic transmission electron microscopy are now in progress. This presentation is based on results obtained from the PEMFC Research and Development Program for “Highly‐Coupled Analysis of Phenomena in MEA and its Constituents and Evaluation of Cell Performance” commissioned by the New Energy and Industrial Technology Development Organization (NEDO). The synchrotron radiation experiments were performed at BL45XU in SPring-8 with the approval of JASRI (Proposal No.2016A1194 and, No.2016B1004). Figure 1