| SELYANCHYN ROMAN（セリャンチン ロマン） | データ更新日：2024.04.04 |
准教授 ／
エネルギー研究教育機構
| 1. | Lingcong Li, Shinta Miyazaki, Ziyang Wu, Takashi Toyao, Roman Selyanchyn, Zen Maeno, Shigenori Fujikawa, Ken-ichi Shimizu, Continuous direct air capture and methanation using combined system of membrane-based CO2 capture and Ni-Ca based dual functional materials, Applied Catalysis B: Environmental, 10.1016/j.apcatb.2023.123151, 123151, 123151, 2023.12, [URL], Direct CO2 capture from the air by membranes (membrane-based DAC, m-DAC) is a promising new technique to achieve CO2 net zero emissions. In addition, a continuous system for CO2 capture and its reduction by hydrogen using coupled reactors has scarcely been investigated. In this study, a new continuous system consisting of a m-DAC and a methanation process (m-DAC-M) was developed. For methanation, Ni nanoparticles supported on Ca-loaded Al2O3 (Ni-Ca/Al2O3; 10 wt% Ni and 6 wt% CaO) were utilized as a dual functional material (DFM). The Ni-Ca/Al2O3 exhibited high CH4 productivity and selectivity, good stability over 100 h, and high humidity resistance properties at a low reaction temperature of 350 °C. The catalytic properties of Ni-Ca/Al2O3 were elucidated using microscopic and spectroscopic techniques. The characterization results indicated that the CaO species not only served as CO2 adsorption sites to trap concentrated CO2 from the m-DAC system but also improved the reducibility of oxidized Ni species in the hydrogenation period, thereby promoting the reduction of surface carbonate species to CH4.. |
| 2. | Sinan Feng, Yokajaksusri Nutthon, Hiroyasu Masunaga, Sono Sasaki, Roman Selyanchyn, Shigenori Fujikawa, Shinichi Murata, and Atsushi Takahara, Controlling Microstructure–Transport Interplay in Poly(ether-block-amide) Multiblock Copolymer Gas Separation Membranes, Langmuir, 10.1021/acs.langmuir.3c02516, 39, 49, 17879-17888, 2023.11, [URL], In this study, we investigated the effect of morphology on the gas-transport properties of a poly(ether-block-amide) (PEBA) multiblock copolymer. We annealed the copolymer samples and varied the annealing temperature to evaluate the influence of changes in the microstructure on the gas transport properties of PEBA. In addition, we used time-resolved attenuated total reflection Fourier transform infrared spectroscopy to evaluate the diffusion coefficient of CO2 in PEBA based on the Fickian model. The effect of the annealing temperature on the microphase-separated structure of the multiblock copolymer is discussed in detail. Furthermore, the gas diffusivity was significantly affected by the purity of the soft domains. The annealed sample demonstrated a 38% increase in CO2 permeability while maintaining a high CO2/N2 permselectivity of approximately 53. The findings of this study provide valuable insight into the design and optimization of PEBA membranes for gas separation applications.. |
| 3. | Hongfang Guo, Jing Wei, Yulei Ma, Zikang Qin, Xiaohua Ma, Roman Selyanchyn, Bangda Wang, Xuezhong He, Bo Tang, Lin Yang, Lu Yao, Wenju Jiang, Yuanfa Zhuang, Dengguo Yin, Xue Li, Zhongde Dai, Carbon molecular sieve membranes fabricated at low carbonization temperatures with novel polymeric acid porogen for light gas separation, SEPARATION AND PURIFICATION TECHNOLOGY, 10.1016/j.seppur.2023.123883, 317, 2023.07, [URL]. |
| 4. | Olena Selyanchyn, Thomas Bayer, Dino Klotz, Roman Selyanchyn, Kazunari Sasaki, Stephen Matthew Lyth, Cellulose Nanocrystals Crosslinked with Sulfosuccinic Acid as Sustainable Proton Exchange Membranes for Electrochemical Energy Applications, MEMBRANES, 10.3390/membranes12070658, 12, 7, 2022.07, Nanocellulose is a sustainable material which holds promise for many energy-related applications. Here, nanocrystalline cellulose is used to prepare proton exchange membranes (PEMs). Normally, this nanomaterial is highly dispersible in water, preventing its use as an ionomer in many electrochemical applications. To solve this, we utilized a sulfonic acid crosslinker to simultaneously improve the mechanical robustness, water-stability, and proton conductivity (by introducing -SO3−H+ functional groups). The optimization of the proportion of crosslinker used and the crosslinking reaction time resulted in enhanced proton conductivity up to 15 mS/cm (in the fully hydrated state, at 120 °C). Considering the many advantages, we believe that nanocellulose can act as a sustainable and low-cost alternative to conventional, ecologically problematic, perfluorosulfonic acid ionomers for applications in, e. fuel cells and electrolyzers.. |
| 5. | Shigenori Fujikawa and Roman Selyanchyn, Direct air capture by membranes, MRS BULLETIN, 10.1557/s43577-022-00313-6, 2022.05. |
| 6. | A. Chapman, E. Ertekin , M. Kubota, A. Nagao, K. Bertsch, A. Macadre, T. Tsuchiyama, T. Masamura, S. Takaki, R. Komoda, M. Dadfarnia, B. Somerday, A. Staykov, J. Sugimura, Y. Sawae, T. Morita, H. Tanaka, K. Yagi, V. Niste, P. Saravanan, S. Onitsuka, K.S. Yoon, S. Ogo, T. Matsushima, G. Tumen-Ulzii, Dino Klotz, D. H. Nguyen, G. Harrington, C. Adachi, H. Matsumoto, L. Kwati, Y. Takahashi, N. Kosem, T. Ishihara, M. Yamauchi, B. Saha, Md. A. Islam, J. Miyawaki, H. Sivasankaran, M. Kohno, S. Fujikawa, R. Selyanchyn, T. Tsuji, Y. Higashi, R. Kirchheim, and P.Sofronis, Achieving a Carbon Neutral Future through Advanced Functional Materials and Technologies, Bulletin of the Chemical Society of Japan, 10.1246/bcsj.20210323, 95, 1, 73-103, 2022.01, [URL]. |
| 7. | Yulei Ma, Hongfang Guo, Roman Selyanchyn, Bangda Wang, Liyuan Deng, Zhongde Dai, Xia Jiang, Hydrogen sulfide removal from natural gas using membrane technology: a review, JOURNAL OF MATERIALS CHEMISTRY A, 10.1039/d1ta04693d, 9, 36, 20211-20240, 2021.09, [URL], ABSTRACT: Natural gas, having a significantly lower CO2 emission factor than oil and coal when combusted, is accepted as an important transition fuel towards carbon net-zero society. To meet the calorific value requirements (≥34.0 MJ m−3) and reduce possible corrosion of transportation pipelines, acid gases such as CO2 and H2S must be removed from raw natural gas. Membrane separation is a promising alternative approach to removing acid gases from natural gas. This paper aims to review the development of various polymer-based membranes and membrane processes for H2S separation from natural gas. Progress in glassy polymer membranes, rubbery polymer membranes, hybrid membranes, and membrane contactors for H2S removal from natural gas are summarized and analyzed. The H2S separation performance of various membranes are plotted in one diagram and a new H2S/CH4 upper bound is proposed. Challenges of membranes for H2S separation and prospects of future development are thoroughly discussed.. |
| 8. | Keiki Inoue, Roman Selyanchyn, Shigenori Fujikawa, Fumitaka Ishiwari, Takanori Fukushima, Thermal and Gas Adsorption Properties of Troger's Base/Diaza-cyclooctane Hybrid Ladder Polymers., ChemNanoMat, 10.1002/cnma.202100151, 7, 7, 824-830, 2021.04, [URL], ABSTRACT: A polymer of intrinsic microporosity (PIM) consisting of Tröger's base (TB) undergoes ring-opening of the bicyclic amine upon N-methylation followed by alkaline hydrolysis, resulting in a hybrid ladder polymer that contains diazacyclooctane (DACO) units with tert- and sec-amino groups. The hybrid ladder polymers with various TB/DACO ratios can be prepared depending on the reaction conditions. Here we report a systematic study on the effect of DACO content on the thermal and gas adsorption properties of the hybrid ladder polymer. Using a PIM derived from 2,5-diamino-p-xylene, we prepared hybrid ladder polymers with a DACO content ranging from 19% to 55% while having a similar molecular weight. The thermal stability of the hybrid ladder polymers, evaluated by thermogravimetric analysis, is decreased with the increase in DACO content. Based on gas adsorption measurements, the increase in DACO content results in the decrease in the BET surface area but improves the gas adsorption selectivity for CO2 against N2, likely due to the high basicity of the sec-amino group of DACO unit. This result demonstrates that the partial TB-to-DACO conversion of the TB-based PIM may provide a simple but useful strategy to design polymer materials that enable selective CO2 capture and/or separation.. |
| 9. | Ievgen Pylypchuk, Roman Selyanchyn, Tetyana Budnyak,Yadong Zhao, Mikael Lindström, Shigenori Fujikawa, Olena Sevastyanova, “Artificial Wood” Lignocellulosic Membranes: Influence of Kraft Lignin on the Properties and Gas Transport in Tunicate-Based Nanocellulose Composites, MEMBRANES, 10.3390/membranes11030204, 11, 3, 2021.03, [URL], ABSTRACT: Nanocellulose membranes based on tunicate-derived cellulose nanofibers, starch, and ~5% wood-derived lignin were investigated using three different types of lignin. The addition of lignin into cellulose membranes increased the specific surface area (from 5 to ~50 m2/g), however, the fine porous geometry of the nanocellulose with characteristic pores below 10 nm in diameter remained similar for all membranes. The permeation of H2, CO2, N2, and O2 through the membranes was investigated and a characteristic Knudsen diffusion through the membranes was observed at a rate proportional to the inverse of their molecular sizes. Permeability values, however, varied significantly between samples containing different lignins, ranging from several to thousands of barrers (10−10 cm3 (STP) cm cm−2 s−1 cmHg −1), and were related to the observed morphology and lignin distribution inside the membranes. Additionally, the addition of ~5% lignin resulted in a significant increase in tensile strength from 3 GPa to ~6–7 GPa, but did not change thermal properties (glass transition or thermal stability). Overall, the combination of plant-derived lignin as a filler or binder in cellulose–starch composites with a sea-animal derived nanocellulose presents an interesting new approach for the fabrication of membranes from abundant bio-derived materials. Future studies should focus on the optimization of these types of membranes for the selective and fast transport of gases needed for a variety of industrial separation processes.. |
| 10. | Thomas Bayer, Benjamin Vaughan Cunning, Břetislav Šmíd, Roman Selyanchyn, Shigenori Fujikawa, Kazunari Sasaki, Stephen Matthew Lyth, Spray deposition of sulfonated cellulose nanofibers as electrolyte membranes in fuel cells, CELLULOSE, 10.1007/s10570-020-03593-w, 28, 3, 1355-1367, 2021.02, [URL], ABSTRACT: Nanocellulose is a promising new membrane material for fuel cells, with a much lower cost and environmental impact compared with Nafion or Aquivion. It is mechanically strong, is an excellent hydrogen barrier, and has reasonable proton conductivity. Here, sulfonation of cellulose nanofibers is performed to enhance the conductivity (up to 2 × 10− 3 S cm− 1) without compromising the membrane integrity, and fuel cells are fabricated with 30 µm-thick “paper” membranes. The hydrogen crossover current is two orders of magnitude lower than for Nafion fuel cells with equivalent thickness, but the power density is rather low. Spray-coating is used to deposit 8 µm-thick membranes directly onto the electrocatalyst layer, in a process analogous to 3D printing or additive manufacturing. The resulting paper fuel cell has a high current density (> 0.8 A cm− 2) and power density (156 mW cm− 2) under standard measurement conditions (H2/air; 80°C; 95% RH; 0.1 MPa), attributed to decreased membrane resistance. The cost of the spray-painted cellulose membranes is calculated to be ~ 50 $ m− 2, which is much lower than that of Nafion, even without taking into consideration economies of scale. This new concept in electrochemical energy conversion paves the way for the mass production of affordable, recyclable fuel cells.. |
| 11. | Shigenori Fujikawa, Roman Selyanchyn, Toyoki Kunitake, A new strategy for membrane-based direct air capture., Polym. J. (Tokyo, Jpn.), 10.1038/s41428-020-00440-4, 53, 1, 219, 2021.01, [URL], ABSTRACT: Direct CO2 capture from the air, so-called direct air capture (DAC), has become inevitable to reduce the concentration of CO2 in the atmosphere. Current DAC technologies consider only sorbent-based systems. Recently, there have been reports that show ultrahigh CO2 permeances in gas separation membranes and thus membrane separation could be a potential new technology for DAC in addition to sorbent-based CO2 capture. The simulation of chemical processes has been well established and is commonly used for the development and performance assessment of industrial chemical processes. These simulations offer a credible assessment of the feasibility of membrane-based DAC (m-DAC). In this paper, we discuss the potential of m-DAC considering the state-of-the-art performance of organic polymer membranes. The multistage membrane separation process was employed in process simulation to estimate the energy requirements for m-DAC. Based on the analysis, we propose the target membrane separation performance required for m-DAC with competitive energy expenses. Finally, we discuss the direction of future membrane development for DAC.. |
| 12. | Olena Selyanchyn, Roman Selyanchyn, Stephen M. Lyth, A Review of Proton Conductivity in Cellulosic Materials, FRONTIERS IN ENERGY RESEARCH, 10.3389/fenrg.2020.596164, 8, 2020.11, [URL], ABSTRACT: Cellulose is derived from biomass and is useful in a wide range of applications across society, most notably in paper and cardboard. Nanocellulose is a relatively newly discovered variant of cellulose with a much smaller fibril size, leading to unique properties such as high mechanical strength. Meanwhile, electrochemical energy conversion in fuel cells will be a key technology in the development of the hydrogen economy, but new lower-cost proton exchange membrane (PEM) materials are needed. Nanocellulose has emerged as a potential candidate for this important application. In this review, we summarize scientific developments in the area of cellulosic materials with special emphasis on the proton conductivity, which is the most important parameter for application in PEMs. We cover conventional cellulose and nanostructured cellulose materials, polymer composites or blends, and chemically modified cellulose. These developments are critically reviewed, and we identify interesting trends in the literature data. Finally, we speculate on future directions for this field.. |
| 13. | Olena Selyanchyn, Roman Selyanchyn, Shigenori Fujikawa, Critical role of the molecular interface in double-layered Pebax-1657/PDMS nanomembranes on highly efficient CO2/N2 gas separation, ACS Applied Materials and Interfaces, 10.1021/acsami.0c07344, 2020.07, [URL], ABSTRACT: In this work, we deposited a CO2-selective block copolymer, Pebax-1657, as a selective layer with a thickness of 2–20 nm on the oxygen plasma-activated surface of poly(dimethylsiloxane) (PDMS) used as a gutter layer (thickness ∼400 nm). This double-layered structure was subsequently transferred onto the polyacrylonitrile (PAN) microporous support and studied for CO2/N2 separation. The effect of interfacial molecular arrangements between the selective and gutter layers on CO2 permeance and selectivity has been investigated. We have revealed that the gas permeance and selectivity do not follow the conventional theoretical predictions for the multilayer membrane (resistance in series transport model); specifically, more selective CO2/N2 separation membranes were achieved with ultrathin selective layers. Detailed characterization of the chemical structure of the outermost membrane surface suggests that nanoscale blending of the ultrathin Pebax-1657 layer with O2 plasma-activated PDMS chains on the surface takes place. This nanoblending at the interface between the selective and gutter layers played a critical role in enhancing the CO2/N2 selectivity. CO2 permeances in the developed thin-film composite membranes (TFCM) were between 1200 and 3500 gas permeance units (GPU) and the respective CO2/N2 selectivities were between 72 and 23, providing the gas separation performance suitable for CO2 capture in postcombustion processes. This interpenetrating polymer interface enhanced the overall selectivity of the membrane significantly, exceeding the separation ability of the pristine Pebax-1657 polymer.. |
| 14. | Shigenori Fujikawa, Miho Ariyoshi, Roman Selyanchyn, Toyoki Kunitake, Ultra-fast, selective CO2 permeation by free-standing siloxane nanomembranes, Chemistry Letters, 10.1246/cl.190558, 48, 11, 1351-1354, 2019.11, [URL], ABSTRACT: Fabrication and gas permselective behavior of free-standing polydimethylsiloxane (PDMS) nanomembranes is discussed. The largest CO2 permeance is close to 40,000 GPU (the highest one ever reported) at 34-nm membrane thickness without losing the CO2/N2 selectivity of 10-12, indicating the formation of pin-hole free nanomembranes.. |
| 15. | Prabakaran Saravanan, Roman Selyanchyn, Hiroyoshi Tanaka, Shigenori Fujikawa, Stephen Matthew Lyth, Joichi Sugimura, The effect of oxygen on the tribology of (PEI/GO)15 multilayer solid lubricant coatings on steel substrates, Wear, 10.1016/j.wear.2019.05.035, 432-433, 2019.08, [URL], ABSTRACT: Multilayers of polyethyleneimine and graphene oxide, (PEI/GO)15, were coated onto steel substrates via electrostatic layer-by-layer (LbL) deposition, and their tribological properties were investigated as solid lubricants. The coefficient of friction (COF) and specific wear rate (SWR) were measured against a poly(methyl methacrylate) (PMMA) counterface ball, in various gas environments with different oxygen concentrations. The COF and SWR both significantly decreased with decreasing oxygen content. Detailed surface characterization of the contact area of the counterface ball revealed that continuous transfer films were formed in oxygen-free environments, but not in oxygen-rich environments. This is attributed to an increased proportion of sp3 bonding in the wear debris in the presence of oxygen (as confirmed by Raman spectroscopy), as well as possible suppression of wear debris adhesion on the counterface ball due to oxygen adsorption on the surface.. |
| 16. | Roman Selyanchyn, Shigenori Fujikawa, Molecular Hybridization of Polydimethylsiloxane with Zirconia for Highly Gas Permeable Membranes, ACS Applied Polymer Materials, 10.1021/acsapm.9b00178, 1, 5, 1165-1174, 2019.05, [URL], ABSTRACT: Inorganic–organic nanocomposite hybrids containing zirconium dioxide (ZrO2) as inorganic cross-linker/filler and polydimethylsiloxane (PDMS) as a polymeric matrix have been synthesized using the in situ sol-gel reaction between silanol-terminated PDMS and zirconium normal butoxide (Zr(OC4H9)4). Hybrid materials were used to fabricate gas separation membranes which were characterized by scanning electron microscopy, dynamic scanning calorimetry, nanoindentation, ATR-FTIR, and XPS spectroscopies. The amorphous structure of incorporated ZrO2 fillers was verified by X-ray diffraction. Small gases (He, H2, O2, N2, and CO2) permeability experiments were carried out to study the effect of the inorganic component amount on the properties of the ZrO2@PDMS hybrids. The permeability of the developed hybrids considerably exceeded the permeability of conventional PDMS which is known as “gold standard” highly gas-permeable rubbery polymer. Depending on the ZrO2 content, fabricated hybrids demonstrated increased permeability for all gases with improvement inversely proportional to the kinetic diameter of gas molecules, that is, the highest permeability increase (relatively to PDMS) was observed for H2 and lowest for N2. Such behavior suggests the formation of the size-sieving amorphous zirconia domains within PDMS which do not impede gas transport due to the nanosize of the fillers. As a result, gas separation membranes prepared using the developed materials demonstrated better separation performance for CO2/N2, H2/N2, and O2/N2 pairs compared to the conventional PDMS.. |
| 17. | Roman Selyanchyn, Shigenori Fujikawa, Naohiro Katsuta, Kazuya Suwa, Masashi Kunitake, Study of Gases Permeation in Necklace-Shaped Dimethylsiloxane Polymers Bearing POSS Cages, Membranes, 9, 4, 1, 2019.04, The transport of small gases (H2, CO2, N2, O2) through a series of novel membranes based on necklace-shaped inorganic polymers (DMS@POSS), in which a polyhedral oligomeric silsesquioxane (POSS) cage unit and soft chains of oligo-dimethyl siloxane (DMS) were alternately connected, was investigated. The influence of the DMS chain length and crosslinking density of the DMS@POSS on membrane properties were studied. The membranes revealed characteristic structure-property relation towards both glass transition and gases transport. Specifically, a clear dependence of properties from the length of DMS units (or overall siloxane content) was revealed. Gas transport properties, when compared to state-of-art polydimethylsiloxane and commercial silicone rubber, demonstrated significantly higher selectivity of DMS@POSS for carbon dioxide (in CO2/N2), hydrogen (in H2/N2) and oxygen (in O2/N2) but lowered permeability, proportional to the amount of POSS in the material. With precise control over mechanical and thermal properties compared to conventional silicone rubbers, described materials could be considered as materials of choice in niche gas separation or other applications.. |
| 18. | Roman Selyanchyn, Miho Ariyoshi, Shigenori Fujikawa, Thickness effect on CO2/N2 separation in double layer Pebax-1657®/PDMS membranes, Membranes, 10.3390/membranes8040121, 8, 4, 2018.12, [URL]. |
| 19. | Prabakaran Saravanan, Roman Selyanchyn, Motonori Watanabe, Shigenori Fujikawa, Hiroyoshi Tanaka, Stephen Matthew Lyth, JoichiSugimura, Ultra-low friction of polyethylenimine / molybdenum disulfide (PEI/MoS2)15 thin films in dry nitrogen atmosphere and the effect of heat treatment, Tribology International, 10.1016/j.triboint.2018.06.003, 127, 255-263, 2018.06, [URL]. |
| 20. | Sergiy Korposh, Suguru Kodaira, Roman Selyanchyn, Francisco H. Ledezma, Stephen W. James, Seung-Woo Lee, Porphyrin-nanoassembled fiber-optic gas sensor fabrication: Optimization of parameters for sensitive ammonia gas detection, Optics & Laser Technology, 10.1016/j.optlastec.2017.10.027, 101, 1-10, 2018.05, [URL]. |
| 21. | Shiyan Feng, Shoichi Kondo, Takahiro Kaseyama, Taichi Nakazawa, Takamasa Kikuchi, Roman Selyanchyn, Shigenori Fujikawa, Liana Christiani, Kazunari Sasaki, Masamichi Nishihara, Development of polymer-polymer type charge-transfer blend membranes for fuel cell application, Journal of Membrane Sciences, 10.1016/j.memsci.2017.11.025, 548, 223-231, 2018.02, [URL]. |
| 22. | Anteneh Mersha, Roman Selyanchyn, Shigenori Fujikawa, Preparation of large, ultra-flexible and free-standing nanomembranes of metal oxide–polymer composite and their gas permeation properties, Clean Energy, 1, 1, 80-89, 2017.12, In this work, fabrication of free-standing nanomembranes of metal oxide (MOx) and polymers by the simple spin-coating method is discussed. First, double-layer nanomembranes containing MOx and epoxy resin of polyethyleneimine and poly[(o-cresyl glycidyl ether)-co-formaldehyde] were prepared. Free-standing nanomembranes were successfully prepared, but defects formed in the metal oxide nanolayer during sharp bending of the nanomembrane. To overcome the fragility of MOx nanolayer, poly(vinyl alcohol) nanolayers were introduced between MOx nanolayers by layer-by-layer (LbL) assembly process. The LbL nanomembrane was also free-standing and was highly flexible during macroscopic membrane manipulations. Even after the transfer of the LbL nanomembrane onto a porous support, it did not have apparent cracks, confirmed by scanning electron microscopy (SEM). The LbL nanomembrane sustained low gas permeance, confirming the absence of significant defects, although it shows excellent flexibility. We believe that the presented LbL nanomembrane could be a platform useful for the design of molecular nanochannels, which is the next challenge for efficient gas separation.. |
| 23. | Prabakaran Saravanan, Roman Selyanchyn, Hiroyoshi Tanaka, Shigenori Fujikawa, Stephen Matthew Lyth, Joichi Sugimura, Ultra-low friction between polymers and graphene oxide multilayers in nitrogen atmosphere, mediated by stable transfer film formation, Carbon, 10.1016/j.carbon.2017.06.090, 122, 395-403, 2017.10, [URL], The efficiency and lifetime of mechanical devices is significantly decreased by friction and wear, significantly contributing to global energy consumption. We previously showed that multilayer polyethyleneimine/graphene oxide thin films, (PEI/GO)15, on steel display superlubricity against a steel counterface ball. Here, the coefficient of friction (COF) and wear of (PEI/GO)15 with six different counterface polymer balls is investigated in air and in nitrogen, with particular focus on the formation of tribological transfer films. The polymers polyoxymethylene (POM), polyetheretherketone (PEEK), polyethylene (PE), poly(methyl methacrylate) (PMMA), polycarbonate (PC), and polytetrafluoroethylene (PTFE) are utilized. The COF of (PEI/GO)15 vs steel is 0.35 in both air and nitrogen. In air, the COF ranges from 0.06 to 0.17 for all polymers. Significantly, in nitrogen, four polymers (POM, PEEK, PMMA and PC) display ultra-low friction (COF ∼0.02) whilst two do not (PTFE and PE). The wear tracks and transfer films are investigated using e.g. optical microscopy, electron microscopy, and Raman mapping, and the tribological behavior is correlated to the hydrophilicity and relative hardness of the polymer balls compared to GO.. |
| 24. | Roman Selyanchyn, Shigenori Fujikawa, Membrane thinning for efficient CO2 capture, Science and Technology of Advanced Materials , 10.1080/14686996.2017.1386531, 18, 1, 816-827, 2017.09, [URL]. |
| 25. | Thomas Bayer, Roman Selyanchyn, Shigenori Fujikawa, Kazunari Sasaki, Stephen M. Lyth, Spray-painted graphene oxide membrane fuel cells, Journal of Membrane Science, 10.1016/j.memsci.2017.07.012, 541, 347-357, 2017.01, [URL], Graphene oxide (GO) is potentially a useful electrolyte material for polymer electrolyte membrane fuel cells due to its high strength, excellent hydrogen gas barrier properties, hydrophilicity, and proton conducting acidic functional groups. Here, GO paper is prepared from aqueous dispersion by vacuum-filtration, and the hydrogen permeability (2 × 10−2 barrer) is measured to be 3 orders of magnitude lower than Nafion (30 barrer) at 30 °C. The in-plane and through-plane conductivities are measured to be 49.9 and 0.3 mS cm−1, respectively. This significant anisotropy is attributed to the lamellar structure of GO, and the physical anisotropy between the thickness and lateral size of the GO nanoplatelets. Interestingly, the in-plane conductivity of GO is comparable to the through-plane conductivity of Nafion. GO membrane fuel cells (GOMFCs) are fabricated. To compensate for the low in-plane conductivity of GO, whilst taking advantage of the excellent hydrogen gas barrier properties, extremely thin electrode-supported GOMFCs are prepared by spray painting GO directly onto the electrocatalyst layer. The effect of membrane thickness on cell performance is investigated. Decreasing membrane thickness by spray painting improves the power density from 3.7 mW cm−2 for a 50 μm-thick membrane-supported GOMFC, to 79 mW cm−2 for a 3 µm-thick, spray-painted membrane, electrode-supported GOMFC.. |
| 26. | Prabakaran Saravanan, Roman Selyanchyn, Hiroyoshi Tanaka, Durgesh Darekar, Aleksandar Staykov, Shigenori Fujikawa, Stephen Matthew Lyth, Joichi Sugimura, Macroscale Superlubricity of Multilayer Polyethylenimine/Graphene Oxide Coatings in Different Gas Environments, ACS Applied Materials and Interfaces, 10.1021/acsami.6b06779, 8, 40, 27179-27187, 2016.10, [URL], Friction and wear decrease the efficiency and lifetimes of mechanical devices. Solving this problem will potentially lead to a significant reduction in global energy consumption. We show that multilayer polyethylenimine/graphene oxide thin films, prepared via a highly scalable layer-by-layer (LbL) deposition technique, can be used as solid lubricants. The tribological properties are investigated in air, under vacuum, in hydrogen, and in nitrogen gas environments. In all cases the coefficient of friction (COF) significantly decreased after application of the coating, and the wear life was enhanced by increasing the film thickness. The COF was lower in dry environments than in more humid environments, in contrast to traditional graphite and diamond-like carbon films. Superlubricity (COF 2. Microstructural analysis of the wear debris revealed that carbon nanoparticles were formed exclusively in dry conditions (i.e., N2, vacuum), and it is postulated that these act as rolling asperities, decreasing the contact area and the COF. Density functional theory (DFT) simulations were performed on graphene oxide sheets under pressure, showing that strong hydrogen bonding occurs in the presence of intercalated water molecules compared with weak repulsion in the absence of water. It is suggested that this mechanism prevents the separation graphene oxide layers and subsequent formation of nanostructures in humid conditions.. |
| 27. | Thomas Bayer, Benjamin V. Cunning, Roman Selyanchyn, Masamichi Nishihara, Shigenori Fujikawa, Kazunari Sasaki, Stephen M. Lyth, High temperature proton conduction in nanocellulose membranes Paper fuel cells, Chemistry of Materials, 10.1021/acs.chemmater.6b01990, 28, 13, 4805-4814, 2016.07, [URL], Polymer electrolyte membrane fuel cells are an efficient and clean alternative power source, but high cost impedes widespread commercialization. The fuel cell membrane, e.g., Nafion, contributes significantly to this cost, and therefore, novel alternatives are required. Temperature is also an important factor; high temperature operation leads to faster reaction kinetics, lower electrocatalyst loading, and improved water management, thereby further reducing cost. However, higher temperature puts greater demands on the membrane. Conductivity is related strongly to humidification, and therefore, this generally decreases above 100 °C. Nanocellulose membranes for fuel cells in which the proton conductivity increases up to 120 °C are reported here for the first time. The hydrogen barrier properties are far superior to conventional ionomer membranes. Fuel cells with nanocellulose membranes are successfully operated at 80 °C. Additionally, these membranes are environmentally friendly and biodegradable.. |
| 28. | Thomas Bayer, Benjamin V. Cunning, Roman Selyanchyn, Takeshi Daio, Masamichi Nishihara, Shigenori Fujikawa, Kazunari Sasaki, Stephen M. Lyth, Alkaline anion exchange membranes based on KOH-treated multilayer graphene oxide, Journal of Membrane Science, 10.1016/j.memsci.2016.02.017, 508, 51-61, 2016.06, [URL], A novel class of alkaline anion exchange membrane (AAEM) is presented, in the form of KOH-modified multilayer graphene oxide paper (GOKOH). Such membranes can be easily fabricated at large scale with varying thickness using conventional filtration techniques, and have high tensile strength (24.5 MPa). However, a large degree of swelling is observed. SEM investigations show that the morphology of GO changes after KOH-treatment, whilst XPS measurements and XRD analysis confirm successful chemical modification. The hydrogen gas permeability is several orders of magnitude lower than conventional polymer-based ionomer membranes. The maximum anion conductivity is 6.1 mS/cm at 70 °C, and the dominant charge carrier is confirmed to be OH- by utilization of anion and proton-conducting blocking layers. The ion exchange capacity is 6.1 mmol/g, measured by titration. A water-mediated reverse Grotthuss-like mechanism is proposed as the main diffusion mode of OH- ions. Finally, a prototype AAEM fuel cell is fabricated using a GOKOH membrane, confirming the applicability to real systems.. |
| 29. | Roman Selyanchyn, Aleksandar Staykov, Shigenori Fujikawa, Incorporation of CO2 philic moieties into a TiO2 nanomembrane for preferential CO2 separation, RSC Advances, 10.1039/c6ra18419g, 6, 91, 88664-88667, 2016.01, [URL], Here we report a preferential CO2 separation membrane consisting of a nanometer-thick TiO2 layer incorporated with phtalic acid (PA) molecules on polydimethylsiloxane (PDMS) (PA@TiO2/PDMS). Incorporated PAs in TiO2 act as CO2-philic pores for preferential CO-2 permeation over nitrogen. CO2 binding to the PA incorporated in TiO2 is confirmed by the density functional theory calculation (DFT). As a result, membranes with of PA@TiO2 layer demonstrated much higher selectivity to CO2 for mixed CO2/N2 gas separation compared to a conventional PDMS membrane. The exceptional selectivity of the composite layer alone (>150) was estimated by a resistance model.. |
| 30. | Yusuke Ogimoto, Roman Selyanchyn, Naoki Takahara, Shunichi Wakamatsu, Seung Woo Lee, Detection of ammonia in human breath using quartz crystal microbalance sensors with functionalized mesoporous SiO2 nanoparticle films, Sensors and Actuators, B: Chemical, 10.1016/j.snb.2015.03.103, 215, 428-436, 2015.08, [URL], Quartz crystal microbalance (QCM) sensors with porous films comprising silica nanoparticles and poly(allylamine hydrochloride) (PAH) were fabricated. The films were deposited via an electrostatic self-assembly method, and they exhibited considerable sensitivity to relative humidity. The infusion of poly(acrylic acid) (PAA) into multi-layer porous films (5 or 10 cycles) enabled the construction of a highly sensitive and selective QCM sensor device for the detection of gaseous ammonia. Two types of QCM sensors, with and without PAA, were used as sensors for the simultaneous quantitative detection of humidity and ammonia. A comprehensive Fourier transform infrared (FTIR) investigation of the fabricated films was conducted to elucidate the mechanism of the chemical interaction at the sensor device interface. Preliminary tests were conducted to detect low concentrations of ammonia in human breath, which are of clinical relevance. The results of these tests showed that the sensor can detect ammonia in human breath at pathological levels (greater than 3 ppm).. |
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