| 1. |
- Iakunkov, Artem, et al.
(författare)
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Swelling of graphene oxide membranes in alcohols : effects of molecule size and air ageing
- 2019
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 7, s. 11331-11337
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Tidskriftsartikel (refereegranskat)abstract
- Swelling of Hummers graphene oxide (HGO) membranes in a set of progressively longer liquid alcohols (methanol to 1-nonanol) was studied using synchrotron radiation XRD after air ageing over prolonged periods of time. Both precursor graphite oxides and freshly prepared HGO membranes were found to swell in the whole set of nine liquid alcohols with an increase of interlayer spacing from ∼7 Å (solvent free) up to ∼26 Å (in 1-nonanol). A pronounced effect of ageing on swelling in alcohols was found for HGO membranes stored in air. The HGO membranes aged for 0.5–1.5 years show progressively slower swelling kinetics, a non-monotonic decrease of saturated swelling in some alcohols and complete disappearance of swelling for alcohol molecules larger than hexanol. Moreover, the HGO membranes stored under ambient conditions for 5 years showed a nearly complete absence of swelling in all alcohols but preserved swelling in water. In contrast, precursor graphite oxide powder showed unmodified swelling in alcohols even after 4 years of ageing. Since the swelling defines the size of permeation channels, the ageing effect is one of the important parameters which could explain the strong variation in reported filtration/separation properties of GO membranes. The time and conditions of air storage require standardization for better reproducibility of results related to performance of GO membranes in various applications. The ageing of GO membranes can be considered not only as a hindrance/degradation for certain applications, but also as a method to tune the swelling properties of HGO membranes for better selectivity in sorption of solvents and for achieving better selective permeability.
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| 2. |
- Järvinen, Topias, et al.
(författare)
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An energy harvester based on UV-polymerized short-alkyl-chain-modified [DBU][TFSI] ionic liquid electrets
- 2023
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496.
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Tidskriftsartikel (refereegranskat)abstract
- Three short-alkyl-chain-modified [DBU][TFSI] ionic liquids (ILs) were synthesized and utilized in electrets. The electrets were prepared by mixing a UV-curable polymer with the ionic liquids followed by polymerization while applying an external electric field, thus forming spatially separated anions and cations in the proximity of opposing surfaces of the composite slabs. The immobilized surplus surface charge was measured by periodically engaging the electret with a metal counter electrode plate and detecting the displacement current using a charge amplifier. The results show that electrets based on polymerized [DBU][TFSI] ILs have a separated surface charge density of up to 64 nC × cm−2, which equals an energy harvesting density of 7.0 nJ × cm−2. Control measurements repeated after a few days to assess the stability and reproducibility of the systems showed that while charge separation reverses over time to some extent, the polymerized ionic liquid samples are resilient to exposure to atmospheric conditions and could be utilized in this type of energy harvesting scheme.
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| 3. |
- Kan, Zhipeng, et al.
(författare)
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Charge transport control via polymer polymorph modulation in ternary organic photovoltaic composites
- 2016
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 4:4, s. 1195-1201
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Tidskriftsartikel (refereegranskat)abstract
- The control on the charge transport properties of ternary organic photovoltaic P3HT : PCBM : QBT devices is enabled by modulating the distribution of P3HT polymorphs in the device photoactive layers. Negligible amounts of QBT induce striking modifications in the P3HT lamellar stacking direction, forming both densely packed and non-densely packed P3HT chains. The former reduce the charge carrier recombination rate, enabling an increased fill factor and short-circuit device photocurrent.
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| 4. |
- Li, Luhan, et al.
(författare)
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Tailoring charge reconfiguration in dodecahedral Co2P@carbon nanohybrids by triple-doping engineering for promoted reversible oxygen catalysis
- 2022
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 10:40, s. 21659-21671
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Tidskriftsartikel (refereegranskat)abstract
- Simultaneously tuning the electronic structure of active sites and the microenvironment of the carbon matrix in metal phosphide/carbon nanohybrids is the most effective way to design and develop bi-functional electrocatalysts for electrochemically related energy storage devices. Inspired by this, a robust and advanced N/P co-doped carbon-based dodecahedron catalyst with confined Fe-doped Co2P particles was successfully prepared through a multi-doping engineering strategy. Phytic acid molecules, which were used in the synthesis of the catalyst, not only contribute to the formation of the porous structure, but also act as a phosphorus source to form the corresponding metal phosphide and the P dopant in the carbon matrix. Thanks to the unique composition and structure-dependent merits, the microenvironment of the electrocatalyst was significantly modulated, thus promoting the advantageous local charge rearrangement and smooth mass/charge transfer processes during the oxygen-related electrocatalytic reactions. As a result, the resultant catalyst exhibited significantly enhanced reversible oxygen activity, as evidenced by an ultra-small potential gap of 0.655 V (half-wave potential of 0.895 V for the oxygen reduction reaction; η10 of 320 mV for the oxygen evolution reaction), a remarkable specific capacity of 762 mA h gZn−1, and high voltaic efficiency, exceeding most previous reports. This study provides a new synthetic approach for fabricating highly efficient bi-functional oxygen catalysts and can be handily extended to the synthesis of other heterogeneous electrocatalysts for sustainable energy storage.
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| 5. |
- Li, Yuanyuan, et al.
(författare)
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Towards centimeter thick transparent wood through interface manipulation
- 2018
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 6:3, s. 1094-1101
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Tidskriftsartikel (refereegranskat)abstract
- Transparent wood is an attractive structural material for energy-saving buildings due to its high optical transmittance, good thermal insulation, and high toughness. However, thick highly transparent wood is challenging to realize. In the current work, highly transparent wood (1.5 mm) with a transmittance of 92%, close to that of pure PMMA (95%), is demonstrated. The high transmittance was realized by interface manipulation through acetylation of wood template. Both experiments and electromagnetic modeling support that the improved transmittance is mainly due to elimination of interface debonding gap. By applying this method, a centimeter-thick transparent wood structure was obtained. The transparent wood could be used as a substrate for an optically tunable window by laminating a polymer dispersed liquid crystal (PDLC) film on top. The techniques demonstrated are a step towards the replacement of glass in smart windows and smart buildings.
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| 6. |
- Li, Ziyao, et al.
(författare)
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Atomic-level orbital coupling in a tri-metal alloy site enables highly efficient reversible oxygen electrocatalysis
- 2023
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 11:5, s. 2155-2167
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Tidskriftsartikel (refereegranskat)abstract
- Complex multi-metallic alloys with ultra-small sizes have received extensive attention in the fields of Zn-air battery and water splitting, because of their unique advantages including adjustable composition, tailorable active sites, and optimizable electronic structure. In this effort, an atomic-level orbital coupling strategy is presented to effectively regulate the electronic structures of ultra-small tri-metal Fe-Co-Ni nanoalloy particles confined in an N-doped carbon hollow nanobox. As expected, the optimal nanoalloy hybrid material exhibited notable bi-functional catalytic performances toward the oxygen reduction reaction (half-wave potential of 0.902 V) and oxygen evolution reaction (1.589 V at 10 mA cm−2) with a small ΔE of 0.687 V, exceeding the precious-metal-based and many previously reported catalysts. Furthermore, the as-assembled Zn-air device also displayed a superior specific capacity of 894 mA h g−1, a maximal power density of 247 mW cm−2, and impressive durability (over 100 hours). Ultraviolet photoelectron spectroscopy and density functional theory calculations revealed that the electronic structures could be finely tuned and optimized through ternary metal alloying, resulting in a suitable d-band center and advantageous interfacial charge-transfer, which in turn could effectively reduce the involved energy barriers in the electrocatalytic process and significantly boost its intrinsic activity of reversible oxygen catalysis. Thus, this work affords an effective method for the rational creation of bi-functional non-noble-metal-based electrocatalysts for sustainable energy technology.
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| 7. |
- Lin, Jhih-Fong, et al.
(författare)
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Trifluoroacetylazobenzene for optical and electrochemical detection of amines
- 2015
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 3:8, s. 4687-4694
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we demonstrate the solution processing of optical and electrochemical dye sensors based on 4-(dioctylamino)-4'-(trifluoroacetyl) azobenzene and its application in sensing different amine compounds. Distinct optical response of the sensors exposed to ammonia, tetramethylammonium hydroxide, ethylamine, cadaverine and putrescine (typical compounds upon the decomposition of proteins) is observed. Incorporation of inkjet deposited thin films of the dye as sensors in food packages of ground meat and salmon is found as a feasible route to detect the appearance of biogenic amines produced by the degrading food products. Furthermore, we demonstrate an electrochemical amine sensor based on (trifluoroacetyl) azobenzene dye added in carbon nanotube-Nafion (R) composites. The electrochemical sensor exploits the reaction between the dye and amines to detect amines in electrolytes, while the carbon nanotubes provide large surface for adsorption and also provide a percolating electrical network for allowing efficient charge transfer at the electrode electrolyte interface.
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| 8. |
- Ng, Chun Hin, et al.
(författare)
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Exploration and optimisation of poly(2,2 ‘-bithiophene) as a stable photo-electrocatalyst for hydrogen production
- 2015
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 3:21, s. 11358-11366
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Tidskriftsartikel (refereegranskat)abstract
- An organic photo-electrochemical catalyst for the hydrogen evolution reaction (HER) based on the conducting polymer, poly(2,2 ‘-bithiophene) (PBTh), is further explored. Long-term stability testing shows the successful operation of the catalyst over a period of 12 days at neutral pH with corresponding turnover numbers exceeding 6 x 10(4). Experimental parameters such as substrate type, electrolyte, pH and thickness of the film are explored and their subsequent effects on catalytic behaviour and performance discussed. Significant findings include the four-fold increase in performance by the reduction of thickness to better facilitate charge transfer and the successful photo-catalysis of the HER at pH 11, with an onset that is 0.14 V below E-0. Faradaic efficiency was also determined with a maximum recorded efficiency of 80% despite known losses such as crossover reactions and H-2 escape from within the system.
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| 9. |
- Nitze, Florian, 1981, et al.
(författare)
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Direct support mixture painting, using Pd(0) organo-metallic compounds - an easy and environmentally sound approach to combine decoration and electrode preparation for fuel cells
- 2014
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 2:48, s. 20973-20979
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Tidskriftsartikel (refereegranskat)abstract
- An inventive, fast and straight-forward approach for the direct preparation of fuel cell electrodes has been developed and tested. Our approach avoids long catalyst preparation and post-synthesis treatment. It reduces the use of chemicals and thereby concomitantly lowers the environmental impact and improves cost efficiency. It combines decoration of the support by palladium nanoparticles with electrode preparation through a simple one-step ink-painting and annealing process. Composites have been investigated by high resolution transmission electron microscopy, scanning electron microscopy, and Xray diffraction. Crystalline particles are well-attached and well-distributed on the support. Particles are of few nanometers in size and spherical for decorated Vulcan whereas they are larger and irregularly shaped for decorated helical carbon nanofibers (HCNFs). Electrodes with a metal loading of 0.8 mg cm(-2) have been tested in a direct formic acid fuel cell. Both the Vulcan and the HCNF electrodes show a similar and high power output of up to 120 mW mg(-1). They also show similar performances in deactivation experiments conducted at 200 mA cm(-2) even when using only high purity grade formic acid. After deactivation the electrodes show no structural damage, making them superior to most commercial catalysts. The electrodes can be completely regenerated to initial activity by simple treatment with water. The easy regeneration process indicates that CO-adsorption on the fuel cell anode catalyst is not the main poisoning mechanism responsible for electrode degeneration.
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| 10. |
- Wu, Ming-Chung, et al.
(författare)
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Photo-Kelvin probe force microscopy for photocatalytic performance characterization of single filament of TiO2 nanofiber photocatalysts
- 2013
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 1:18, s. 5715-5720
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Tidskriftsartikel (refereegranskat)abstract
- This is an in-depth study on the photocatalytic performance characterization for single filament of TiO2 nanofiber photocatalysts by the novel photo-Kelvin probe force microscopy technique (photo-KPFM) and first principles calculations. Three kinds of TiO2 nanofibers: anatase TiO2 nanofibers (anatase TiO2 NFs), nitrogen doped TiO2 nanofibers (N-TiO2 NFs), and nitrogen doped TiO2 nanofibers decorated with platinum nanoparticles (N-TiO2-Pt NFs) were investigated. The N-TiO2-Pt NFs exhibit the largest negative photo surface potential shift (-182 mV) as compared to anatase TiO2 NFs (-29 mV). The first-principles calculations based on density functional theory (CASTEP simulation software) indicate that the significant photo surface potential shift obtained by adding nitrogen and platinum into TiO2 NFs is induced by two mechanisms: (1) enhancement in absorbance to increase exciton generation and (2) decreased charge recombination to increase surface charge. These changes in the photo surface potential of various TiO2 nanofibers are closely correlated with their photocatalytic activity. Thus, this novel photo-KPFM provides a useful technique to easily monitor the photocatalytic capability of materials in the development of high performance photocatalysts.
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