| 1. |
- Alkadir Abdulahi, Birhan, 1985, et al.
(författare)
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Structural engineering of pyrrolo[3,4-: F] benzotriazole-5,7(2 H,6 H)-dione-based polymers for non-fullerene organic solar cells with an efficiency over 12%
- 2019
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 7:33, s. 19522-19530
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we have synthesized two wide band gap donor polymers based on benzo[1,2-b:4,5-b′]dithiophene (BDT) and pyrrolo[3,4-f]benzotriazole-5,7(2H,6H)-dione (TzBI), namely, PBDT-TzBI and PBDT-F-TzBI and studied their photovoltaic properties by blending them with ITIC as an acceptor. Polymer solar cell devices made from PBDT-TzBI:ITIC and PBDT-F-TzBI:ITIC exhibited power conversion efficiencies (PCEs) of 9.22% and 11.02% and while annealing at 160 °C, improved the device performances to 10.24% and 11.98%, respectively. Upon solvent annealing with diphenyl ether (DPE) (0.5%) and chlorobenzene (CB), the PCE of the PBDT-F-TzBI-based device increased to 12.12%. The introduction of the fluorinated benzodithiophene (BDT-F) moiety on the backbone of PBDT-F-TzBI improved the open circuit voltage, short circuit current and fill factor simultaneously. The high PCEs of the PBDT-F-TzBI:ITIC-based devices were supported by comparison and analysis of the optical and electronic properties, the charge carrier mobilities, exciton dissociation probabilities, and charge recombination behaviors of the devices.
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| 2. |
- Burks, Terrance, 1969-
(författare)
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Application of Nanomaterials for the Removal of Hexavalent Chromium and their Biological Implications
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The International Agency for Research on Cancer (IARC) stated that chromium in the form of Cr(VI) has been deemed to be a class-A human carcinogen. It has been a major contaminant associated with wastewater. Moreover, the existence of heavy metals in aquatic systems is a critical concern for the environment as well as industries that manufacture or consume these particular elements. In order to remove these particular toxic metals, several well-known conventional methods including ion-exchange, filtration and adsorption are used. Amongst these methods, adsorption offers significant advantages such as the low-cost materials, ease of operation and efficiency in comparison to the other conventional methods.The aim of this work was to develop nanomaterials (particles and fibers) to address some critical issues for the treatment of heavy metals, especially chromium in aqueous systems. Furthermore, the use of nanomaterials and how they relate to nanoscale operations at the biological level has generated considerable concerns in spite of their novel properties.The first part of this thesis deals with the synthesis and characterizations of Fe3O4, magnetite, as nanoparticles which were further coated with surfactants bis(2,4,4-trimethylpentyl)dithiophosphinic acid, Cyanex-301, and 3-Mercaptopropionic acid with the active compound being the thiol (SH) groups, that will suffice as a viable material for Cr(VI) removal from aqueous solutions. The proposed mechanism was the complexation between the thiol group on Cyanex-301 and 3-Mercaptopropionic acid, respectively. The effect of different parameters on the adsorption including contact time, initial and final Cr(VI) ion concentration and solution pH was investigated.The second part of this thesis encompassed the fabrication of flexible nanocomposite materials, with a large surface area and architecture for the removal of Cr(VI) in batch and continuous flow mode. A technique known as electrospinning was used to produce the nanofibers. The flexible yet functional materials architecture has been achieved by growing ZnO nanorod arrays through chemical bath deposition on synthesized electrospun poly-L-lactide nanofibers. Moreover, polyacrylonitrile nanofibers (PAN) were synthesized and adapted by the addition of hydroxylamine hydrochloride to produce amidoxime polyacrylonitrile nanofibers (A-PAN). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to identify the morphologies and particle sizes whereas Fourier-Transform Infrared spectroscopy (FT-IR) was used to identify either the presence or absence of functional groups for the formation of PAN and A-PAN nanofibers. The optimization of functionalized nanoadsorbents to adsorb Cr(VI) was also carried out to investigate the effect of experimental parameters: contact time, solution pH, initial, final and other metal ion concentration. Commercially manufactured pristine engineered (TiO2, ZnO and SiO2) nanoparticles and lab-made functionalized (Fe3O4 and CeO2) nanoparticles were studied while the powders were suspended in appropriate media by Dynamic Light Scattering (DLS) to identify their cytotoxicity effects.
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| 3. |
- Burks, Terrance, et al.
(författare)
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ZnO-PLLA Nanofiber Nanocomposite for Continuous Flow Mode Purification of Water from Cr(VI)
- 2015
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Ingår i: Journal of Environmental and Public health. - : Hindawi Publishing Corporation. - 1687-9805 .- 1687-9813. ; 2015
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Tidskriftsartikel (refereegranskat)abstract
- Nanomaterials of ZnO-PLLA nanofibers have been used for the adsorption of Cr(VI) as a prime step for the purification of water.The fabrication and application of the flexible ZnO-PLLA nanofiber nanocomposite as functional materials in this well-developedarchitecture have been achieved by growing ZnO nanorod arrays by chemical bath deposition on synthesized electrospun poly-Llactidenanofibers. The nanocomposite material has been tested for the removal and regeneration of Cr(IV) in aqueous solutionunder a “continuous flow mode” by studying the effects of pH, contact time, and desorption steps.Theadsorption of Cr(VI) speciesin solution was greatly dependent upon pH. SEM micrographs confirmed the successful fabrication of the ZnO-PLLA nanofibernanocomposite.Theadsorption and desorption of Cr(VI) species were more likely due to the electrostatic interaction between ZnOand Cr(VI) ions as a function of pH.The adsorption and desorption experiments utilizing the ZnO-PLLAnanofiber nanocompositehave appeared to be an effective nanocomposite in the removal and regeneration of Cr(VI) species.
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| 4. |
- Han, Ruiping, et al.
(författare)
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Review on Heat-Utilization Processes and Heat-Exchange Equipment in Biogas Engineering
- 2016
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Ingår i: Journal of Renewable and Sustainable Energy. - : AIP Publishing. - 1941-7012. ; 8:3
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Tidskriftsartikel (refereegranskat)abstract
- With the increasing demand for environmental protection and renewable energy, bioenergy technology has been attracting considerable attention. Anaerobic digestion (AD) is the process to convert the low-grade biomass into bioenergy, in which both heat-recovery and -recycling should be treated carefully in order to improve the process efficiency. In this work, the heat-recovery and its utilization processes were reviewed, and different types of heat exchangers as well as their advantages in biogas engineering were surveyed. It shows that the recovery and utilization of the waste heat from biogas plants with an internal system, such as slurry effluent unit, the combined heat and power unit, the sanitation unit, and the internal recycle unit, are important for improving the AD efficiency of biogas production. For example, the recovery and recycling of waste heat from the effluent can result in a 2-3 °C temperature increase for the inlet manure slurry. For thermophilic AD, the heat recovery from effluent can save about 50% of the total heat requirement. The external heating process is more suitable for large- and medium-scale biogas plants, and the heat transfer coefficient of external heating (850-1000 W/m2 K-1) is almost two-times higher than that of the internal heating (300-400 W/m2 K-1). To utilize the waste heat in biogas plants, heat exchangers have been designed for biogas slurry. However, further improvement on the heat exchangers with anti-blockage, anti-fouling, high efficiency, and low investment is still needed. Moreover, the heat exchanger suitable for a low-temperature-difference system is specially needed in China, but the development is still in its infancy. Therefore, to tailor to the Chinese national conditions, special external heating processes should be designed and reoriented to the diversity of biomass, the climatic environmental conditions, and the renewable Chinese policies
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| 5. |
- Jukka-Pekka, Spets, et al.
(författare)
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Test of Different Anode Electrocatalysts for Direct Glucose Anion Exchange Membrane Fuel Cell
- 2016
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Ingår i: International Journal of Electrochemical Science. - : Electrochemical Science Group. - 1452-3981. ; 11:6, s. 4219-4230
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Tidskriftsartikel (refereegranskat)abstract
- Direct glucose anion exchange membrane fuel cell (AEMFC) with near-neutral-state electrolyte of 0.1 M [PO4] (tot) was studied with five different anode electrocatalysts (Pt, PtRu, PtNi, Au, PdAu) at a temperature of 37 degrees C and at a glucose concentration of 0.1 M. The cathode catalyst in each test was Pt supported on carbon (60 wt.%). Four anode electrocatalysts (supported on carbon) had a total metal content of 40 wt.% while the fifth anode material of PtRu had a higher content of 60 wt.%. Moreover, in order to show the influence of the metallic content on the fuel cell performance, anode catalysts with 60 wt.% (Pt) and 10wt.% (PtNi) were tested. The operation of the AEMFC was controlled by means of an in-house-made electronic load with PI-controller (i.e. a feedback controller that has proportional and integral action on control error signal) either at constant current (CC) or at constant voltage (CV). The primary objective was to characterize the Coulombic efficiency (CE) based on the exchange of two electrons and compare the specific energy (Wh kg(-1)) for the direct glucose AEMFC related to the different electrode combinations and electrocatalysts. As a result of these screening tests, two most efficient anode electrodes with Pt and PtNi were selected to be used for further AEMFC studies.
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| 6. |
- Jukka-Pekka, Spets, et al.
(författare)
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Towards an Efficient Direct Glucose Anion Exchange Membrane Fuel Cell System with Several Electro-Oxidation Units
- 2017
-
Ingår i: International Journal of Electrochemical Science. - : ESG. - 1452-3981. ; 12:5, s. 3697-3708
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Tidskriftsartikel (refereegranskat)abstract
- This work covers the direct glucose anion exchange membrane fuel cell (AEMFC) with near-neutralstate electrolyte of 0.1 M [PO4] (tot) having two high-performing anode electrocatalysts (Pt and PtNi) at 37 degrees C and at a glucose concentration of 0.1 M. The cathode catalyst in each test was a Pt supported on carbon (60 wt.%). The PtNi/C had a total metal content of 40 wt.% and the Pt/C 60 wt.%. The operation of the AEMFC was controlled by means of an in-house made electronic load with PI-controller (i.e. a feedback controller, which has proportional and integral action on control error signal). There were two primary objectives with this study. At first, to find out how the electrode modifications of the anode (i.e. by increasing the thicknesses of these electrodes by adding extra carbon) affect the Coulombic efficiency (CE, based on the exchange of two electrons) and the specific energy (SPE, Wh kg(-1)) values of the direct glucose AEMFC. Secondly, investigate how a two-stage fuel cell system with two fuel cells concatenated and used one after the other for the electrochemical oxidation of glucose, influence the CE and SPE values. The results show that the modified PtNi anode shows superior results for the AEMFC compared to our earlier results. As for the two-stage fuel cell system, it increased the average electric power (mWh) and SPE when compared to single fuel cell systems except when the higher selective anode catalyst (Pt) was used in the first fuel cell prior to the fuel cell in the second fuel cell containing the lower selective anode catalyst (PtNi).
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| 7. |
- Menya, E., et al.
(författare)
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Characterization and alkaline pretreatment of rice husk varieties in Uganda for potential utilization as precursors in the production of activated carbon and other value-added products
- 2018
-
Ingår i: Waste Management. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0956-053X .- 1879-2456. ; 81, s. 104-116
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Tidskriftsartikel (refereegranskat)abstract
- In this study, 13 rice husk (RH) varieties from 4 agro-ecological zones in Uganda were characterized, NaOH-pretreated, and evaluated for their potential utilization as precursors for production of bio-oil, ash, char, and activated carbon for selected applications. RH varieties were characterized through particle size analysis, bulk density, proximate and ultimate analyses, specific surface area, pore volume, as well as lignocellulosic and inorganic compositions. Selected RH varieties were subsequently pretreated at NaOH concentrations of 1-4%w/v, using pretreatment ratios of 5 g RH: 40 mL NaOH. Properties varied among RH varieties, suiting them as feedstocks for different applications. Upland rice husk varieties are more suited precursors for production of bio-oil, and activated carbon due to their relatively lower ash content, higher specific surface area, as well as higher volatile matter and fixed carbon contents. Upland rice husks could as well be employed in the preparation of electrodes for electrochemical devices, due to their relatively higher specific surface area. A high ash content (21-32% dry basis) of lowland rice husks presents good prospects for their calcination, since larger amounts of rice husk ash could be obtained, and employed in different applications. Lowland rice husk varieties could also be more suited precursors for production of char for soil amendment, due to their relatively higher ash content, which subsequently increases their char yields. However, alkaline pretreatment of rice husks using 2-4%w/v NaOH can reduce the ash content by as much as 74-93%, depending on the rice husk variety, which paves way for utilizing rice husks with a high ash content in different applications. Aside from ash reduction, the enhanced specific surface area (1.2-1.7 m(2) g(-1)), volatile matter (68-79%db) and fixed carbon (19-24%db) contents of NaOH-pretreated rice husks suggests they are more suited feedstocks than when employed in their raw form, for production of bio-oil, as well as activated carbon.
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| 8. |
- Menya, E., et al.
(författare)
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Production and performance of activated carbon from rice husks for removal of natural organic matter from water : A review
- 2018
-
Ingår i: Chemical engineering research & design. - : Institution of Chemical Engineers. - 0263-8762 .- 1744-3563. ; 129, s. 271-296
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Forskningsöversikt (refereegranskat)abstract
- Adsorption by activated carbon has great potential to improve natural organic matter (NOM) removal from water. However, the high production and regeneration costs limit its wide scale application. To address these limitations, research efforts have been focused on finding low cost materials that can be transformed into activated carbon. Rice husk is one of such materials of research focus, especially in the developing countries, where over 96% of rice husks are generated globally. Although numerous investigations have been made concerning the production of activated carbon from rice husks, the existing scientific information still remains widely scattered in literature. Furthermore, the scientific information regarding performance of rice husk activated carbon during NOM removal from water still remains poorly documented. This review article therefore provides ample information on efforts made by various researchers concerning production of activated carbon from rice husks and its adsorption performance in relation to NOM removal from water. Properties and pretreatment of rice husks in relation to production of activated carbon are discussed. Activation of rice husks by physical and chemical methods under numerous conditions is reviewed. Factors affecting NOM adsorption by activated carbon are briefly discussed. Adsorption performance of rice husk activated carbon is also reviewed with respect to NOM removal from water, and where possible compared with other source derived activated carbons. The data from literature revealed that NOM removal by rice husk activated carbon can be as effective as commercial activated carbon. Consequently, rice husk activated carbon has potential to serve as an alternative to commercial activated carbon.
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| 9. |
- Ossman, M.E., et al.
(författare)
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Preparation, Characterization and Adsorption Evaluation of old Newspaper Fibres using Basket Reactor (Nickel Removal by Adsorption)
- 2016
-
Ingår i: International Journal of Environmental Research. - : University of Tehran. - 1735-6865 .- 2008-2304. ; 10:1, s. 119-130
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Tidskriftsartikel (refereegranskat)abstract
- In this work, old newspaper fibers (ONF) bleached with H2O2, treated with KOH and treatedwith NaOCl were investigated as potential adsorbents. The characterization of the produced fibers using FTIR,SEM and particle size distribution have been carried out and tested for the removal of Ni (II) from aqueoussolutions. The results indicated that the fibers treated with KOH give the highest %removal of Ni (II) with 88%. Two different reactor designs (batch and basket reactor) with different variables were studied. The results indicated that the equilibrium time was 30 min. and the removal of Ni (II) increased significantly as the pH increased from 2.0 to 6.0 and decreased at pH range of 6.5–8.0. The adsorption of Ni (II) onto ONF treatedwith KOH using batch and basket reactors follows the Langmuir isotherm. The pseudo second order kineticmodel provided good correlation for the adsorption of Ni (II) onto ONF treated with KOH for both batch and basket reactors.
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| 10. |
- Paulraj, Alagar R., 1989-, et al.
(författare)
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Core/shell structure nano-iron/iron carbide electrodes for rechargeable alkaline iron batteries
- 2017
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Ingår i: Journal of the Electrochemical Society. - : Electrochemical Society. - 0013-4651 .- 1945-7111. ; 164:7, s. A1665-A1672
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we have studied a 2% copper substituted core shell type iron/iron carbide as a negative electrode for application in energy storage. The NanoFe-Fe3C-Cu delivered 367 mAh g−1 at ≈80% current efficiency, successfully running for over 300 cycles. The superior electrode kinetics and performance were assessed by rate capability, galvanostatic, potentiodynamic polarization measurements in 6 M KOH electrolyte and at ambient temperature. Ex-situ XRD characterizations and SEM images of both the fresh and used electrode surfaces show that nanoparticles were found to be still intact with negligible particle agglomeration. The electrodes have shown stable performances with low capacity decay, whereas sulfur dissolution from the additive Bi2S3 was found to decrease the charging efficiency with time. This core-shell type structured nano material is, consequently, an auspicious anode candidate in alkaline-metal/air and Ni-Fe battery systems.
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| 11. |
- Paulraj, Alagar Raj, et al.
(författare)
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Electrochemical Performance and in Operando Charge Efficiency Measurements of Cu/Sn-Doped Nano Iron Electrodes
- 2019
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Ingår i: Batteries. - : MDPI. - 2313-0105. ; :1
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Fe-air or Ni-Fe cells can offer low-cost and large-scale sustainable energy storage. At present, they are limited by low coulombic efficiency, low active material use, and poor rate capability. To overcome these challenges, two types of nanostructured doped iron materials were investigated: (1) copper and tin doped iron (CuSn); and (2) tin doped iron (Sn). Single-wall carbon nanotube (SWCNT) was added to the electrode and LiOH to the electrolyte. In the 2 wt. % Cu + 2 wt. % Sn sample, the addition of SWCNT increased the discharge capacity from 430 to 475 mAh g−1, and charge efficiency increased from 83% to 93.5%. With the addition of both SWCNT and LiOH, the charge efficiency and discharge capacity improved to 91% and 603 mAh g−1, respectively. Meanwhile, the 4 wt. % Sn substituted sample performance is not on par with the 2 wt. % Cu + 2 wt. % Sn sample. The dopant elements (Cu and Sn) and additives (SWCNT and LiOH) have a major impact on the electrode performance. To understand the relation between hydrogen evolution and charge current density, we have used in operando charging measurements combined with mass spectrometry to quantify the evolved hydrogen. The electrodes that were subjected to prolonged overcharge upon hydrogen evolution failed rapidly. This insight could help in the development of better charging schemes for the iron electrodes.
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| 12. |
- Paulraj, Alagar R., 1989-, et al.
(författare)
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La0.1Ca0.9MnO3/Co3O4 for oxygen reduction and evolution reactions (ORER) in alkaline electrolyte
- 2018
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Ingår i: Journal of Solid State Electrochemistry. - : Springer-Verlag New York. - 1432-8488 .- 1433-0768. ; , s. 1-14
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Tidskriftsartikel (refereegranskat)abstract
- Non-precious metal bifunctional catalysts are of great interest for metal–air batteries, electrolysis, and regenerative fuel cell systems due to their performance and cost benefits compared to the Pt group metals (PGM). In this work, metal oxides of La0.1Ca0.9MnO3 and nano Co3O47 catalyst as bifunctional catalysts were used in oxygen reduction and evolution reactions (ORER). The catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N2 adsorption isotherms. The electrocatalytic activity of the perovskite-type La0.1Ca0.9MnO3 and Co3O4 catalysts both as single and mixtures of both were assessed in alkaline solutions at room temperature. Electrocatalyst activity, stability, and electrode kinetics were studied using cyclic voltammetry (CV) and rotating disk electrode (RDE). This study shows that the bifunctional performance of the mixed La0.1Ca0.9MnO3 and nano Co3O4 was superior in comparison to either La0.1Ca0.9MnO3 or nano Co3O4 alone for ORER. The improved activity is due to the synergistic effect between the La0.1Ca0.9MnO3 and nano Co3O4 structural and surface properties. This work illustrates that hybridization between these two metal oxides results in the excellent bifunctional oxygen redox activity, stability, and cyclability, leading to a cost-effective application in energy conversion and storage, albeit to the cost of higher catalyst loadings.
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| 13. |
- Paulraj, Alagar Raj, 1989-, et al.
(författare)
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NiFeOx as a Bifunctional Electrocatalyst for Oxygen Reduction (OR) and Evolution (OE) Reaction in Alkaline Media
- 2018
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Ingår i: Catalysts. - : MDPI AG. - 2073-4344. ; 8:8
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Tidskriftsartikel (refereegranskat)abstract
- This article reports the two-step synthesis of NiFeOx nanomaterials and their characterization and bifunctional electrocatalytic activity measurements in alkaline electrolyte for metal-air batteries. The samples were mostly in layered double hydroxide at the initial temperature, but upon heat treatment, they were converted to NiFe2O4 phases. The electrochemical behaviour of the different samples was studied by linear sweep voltammetry and cyclic voltammetry on the glassy carbon electrode. The OER catalyst activity was observed for low mass loadings (0.125 mg cm−2), whereas high catalyst loading exhibited the best performance on the ORR side. The sample heat-treated at 250 °C delivered the highest bi-functional oxygen evolution and reduction reaction activity (OER/ORR) thanks to its thin-holey nanosheet-like structure with higher nickel oxidation state at 250 °C. This work further helps to develop low-cost electrocatalyst development for metal-air batteries
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| 14. |
- Paulraj, Alagar Raj, 1989-
(författare)
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Studies on Rechargeable Fe-air electrodes in Alkaline electrolyte
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Energy storage system is an important component in the energy system based on variable renewable energy sources into the grid. Energy storage system could contribute to decarbonization, energy security, offset the demand and supply of the electricity sector, especially for the electric grid. These can be either mechanical, electrochemical, chemical, electromagnetic or thermal devices. The most important functional characteristics of an energy storage system are capital cost, roundtrip efficiency, energy and power rating, response times and cycle life. Electrochemical energy storage systems (EES) have the following edge over the other systems: fast response time, relatively short duration of storage, size, high efficiency, a decentralized installation which is closer to generation or consumption site.The focus of this thesis is on the development of cost-effective iron anode materials and electrocatalytic air electrodes for Fe-air batteries that potentially could become as an energy storage system. Iron-based systems are attractive due to their safety, cheapness, non-toxicity and ubiquitous availability of materials. However, both the anode and cathode parts have numerous drawbacks that need to be addressed. The anode exhibits poor charge efficiency, rate capability and low capacity utilization while the cathode has sluggish kinetics, poor activity, structural stability and the numbers of active non-noble metal catalysts are limited.This work utilized Cu and Sn-doped iron nanomaterials and different additives (Bi2S3, CNT, LiOH) to enhance the performance of the iron electrode. The performance of the electrodes were evaluated using the charge/discharge cycling, rate capability, cyclic voltammetry (CV), galvanostatic and potentiodynamic polarization measurements, in operando charging measurements combined with mass spectrometry. The fresh and cycled electrodes and powders were characterized by ex-situ XRD, BET, SEM, TEM , XPS and Raman spectroscopy. The most striking results are the prevention of nanoparticle agglomeration, increased charging efficiency (80-91%), effect of Cu and Sn dopants on specific capacity (367-603 mAh g-1) and improved performance of the electrodes at high charge current densities.In the subsequent air electrode part, non-precious metal La-doped CaMnOx, nano Co3O4 and NiFeOX electrocatalysts were synthesized using co-precipitation and hydrothermal methods. Both the single and mixed catalysts were used as bi-functional catalysts for oxygen reduction and evolution reactions (ORER). The catalysts were characterized by XRD, SEM, TEM, BET, Raman and XPS. The electrocatalytic activity and stability were assessed in alkaline solutions on gas diffusion electrodes and glassy carbon electrode by linear sweep voltammetry (LSV), CV and rotating disk electrode (RDE). Furthermore, the mixed catalyst and NiFeOX showed excellent bifunctional performance such as high activity and stability achieved by the hybridization of the two catalysts and the effect of catalyst loading on the electrocatalytic performance. These findings can help to develop a cost-effective material for Fe-air batteries.
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| 15. |
- Solis, Jerry L., et al.
(författare)
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Biodiesel from rapeseed oil (Brassica napus) by supported Li2O and MgO
- 2017
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Ingår i: International Journal of Energy and Environmental Engineering. - : Springer Nature. - 2008-9163 .- 2251-6832. ; 8:1, s. 9-23
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Tidskriftsartikel (refereegranskat)abstract
- Vegetable oils are a vast triglyceride sourcefor biodiesel production; i.e. fatty acid methyl esters(FAME), with methanol and a catalyst via transesterification reaction. The aim of this work was to study heterogeneously catalysed biodiesel production with solid oxides such as mayenite (Ca12Al14O33) and alumina(Al2O3) as catalyst carriers using edible rapeseedoil as feedstock. These oxides were impregnated to have Li2O and MgO concentrations of 5–10 and 5–30 wt% oneach carrier, respectively. The catalysts were characterized using N2-physisorption (BET/BJH), scanning electronmicroscopy (SEM), and X-ray diffraction (XRD)analyses. The synthesized catalysts were mesoporous ranging from 119 to 401 A ° and their chemical phase composition was confirmed by the XRD. The catalyst coating (MgO/Li2O) was studied, along with the catalyst amount in the reactor and the assessment of the transesterification reaction kinetics. The reaction was studiedat 60 C, atmospheric pressure, agitation rate of180 rpm, and a reaction time of 2 h in a 6:1 molar ratioof methanol to oil. For each catalyst, loadings of 2.5, 5,and 10 wt% relative to the oil weight were evaluated.The highest biodiesel yield was obtained by 5 wt%(relative to oil weight) impregnated mayenite catalyst coated with 10 wt% of Li2O. The kinetic data fits to a pseudo-first-order model having a reaction rate constantequal to 0.045 min-1 under these mild reaction conditions.
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| 16. |
- Solis, Jerry L., et al.
(författare)
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Calcium and tin oxides for heterogeneous transesterification of Babasssu oil (Attalea speciosa)
- 2016
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Ingår i: Journal of Environmental Chemical Engineering. - : Elsevier. - 2213-3437. ; 4:4, s. 4870-4877
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Tidskriftsartikel (refereegranskat)abstract
- Non-edible oils and waste cooking oils are alternatives to uphold a sustainable large scale production of biodiesel considering large volumes and by-products. Babassu oil (Attalea speciosa) offers a challenging case study scenario for the preparation of a heterogeneous catalytic material. This study shows the binary synthesis of calcium and stannic oxide (CaO/SnO2) catalysts for transesterification of oils with high content of free fatty acids (FFAs). The catalysts were prepared with several mass ratios of CaO:SnO2 in the proportions of 1:4, 4:1, 7:3 and 1:1. The catalysts were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and N2-physisorption analyses. Biodiesel production was tested using a 23 full factorial design with variables such as temperature, methanol/oil molar ratio, and catalyst weight relative to oil. Such design statistically proved that there was no significant effect over the response variable. Furthermore a Box-Behnken design surface response analysis using the same three variables with three levels was performed with MATLAB showing a non-linear relation and statistical response of the optimal conditions for biodiesel production. The optimal experimental conditions were found to be 54.1°C, agitation speed at 250rpm with 6wt.% of CaO/SnO2 (7:3 mass ratio of the binary catalyst) and 10:1 (methanol:oil) molar ratio. The catalyst has shown a high potential for conversion of Babassu oil by fine-tuning as a single step by simultaneous esterification and transesterification to biodiesel.
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| 17. |
- Solis, Jerry Luis
(författare)
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Conversion processes for biofuel production
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Despite the global positive impacts of soybean-, maize- and sugarcane-based (first-generation) liquid biofuels, several drawbacks pertaining to increased use of agricultural land, causing deforestation in some countries and extensive practice of fertilizers have been observed. As a result, developing advanced (second- and third-generation) liquid biofuels have been identified as better alternatives and are considered to be of great importance in the future. These alternative biofuels will help to meet the energy demand by transition to ameliorate and fulfil the energy demand, especially in the transport sector.The actual energy demand for fossil fuels in Bolivia is unsustainable due to its continuous increase. Bolivia has its own fossil fuel resources, but these still fall short of demand, forcing the government to budget for yearly fuel imports. This situation has prompted attempts to achieve energy independence through the production of biofuels. However, it is important that Bolivian energy independence endeavours include a sustainable vision. Bolivia has great potential for local first- and second-generation liquid biofuel production. However, the intensification of liquid biofuel production should focus on second- and third-generation biofuel production to minimize direct and indirect undesired impacts.This thesis considers the development of suitable technology and procedures to produce second-generation liquid biofuels, which can be divided into biodiesel and ethanol production. The proposed biodiesel production includes the development of heterogeneous catalysts that enable the production of biodiesel from edible and non-edible oils (i.e. rapeseed, babassu, and Ricinus oils). These heterogeneous catalysts are based on gel-based mayenite and alumina supports with the co-precipitation of metal oxides of calcium, lithium, magnesium and tin. The synthesized catalysts were characterized using, N2 physisorption, X-ray powder diffraction, scanning electron microscopy, and thermogravimetric analysis (TGA). The experimental design and optimum results indicate that heterogeneous biodiesel production is feasible, being able to produce biodiesel yields ranging from 85% to 100%. Ethanol production was studied using the residues of Schinus molle seeds after the essential oil extraction process, which is available in excess in Bolivia. The biomass was characterized to elucidate its properties using high-performance liquid chromatography and TGA. The biomass was pre-treated with chemical, physical, andVIenzymatic hydrolysis to increase the fermentation yield. To obtain the highest ethanol production, two native yeast strains were isolated and characterized. By using native yeast strains, a high content of ethanol per gram of biomass was achieved. The proposed implementation of the fermentation process could result in a significant global warming potential reduction. The implementation of heterogeneous catalysts to produce biodiesel and residual lignocellulosic biomass to produce ethanol represent a great potential to supply the Bolivian fuel demand. High biodiesel and ethanol yields from second-generation feedstocks are feasible and could help reduce pollution levels and import dependency.
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| 18. |
- Soroka, Inna, et al.
(författare)
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Radiation-induced synthesis of nanoscale Co-and Ni-based electro-catalysts on carbon for the oxygen reduction reaction
- 2017
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Ingår i: Dalton Transactions. - London, Storbritannien : Royal Society of Chemistry. - 1477-9226 .- 1477-9234. ; 46:30, s. 9995-10002
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Tidskriftsartikel (refereegranskat)abstract
- A facile synthesis of 3d-metal based electro-catalysts directly incorporated into a carbon support was carried out by.-radiation. Transition metals of period 4, i.e. Ni and Co, were precipitated and reduced from their respective salt solutions. The obtained materials were characterized by XRD, SEM, SQUID and the BET methods. Thereafter, the electrodes for fuel cells were fabricated out of synthesized material and their electrochemical performance for the oxygen reduction reaction in 6 M KOH was measured. Although the concentrations of Co and Ni in the electrode material were low (3.4% Co and 0.4% Ni) after reduction by irradiation, both the Ni and Co-based gas diffusion electrodes showed high catalytic activity for oxygen reduction both at room temperature and at 60 degrees C.
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| 19. |
- Tehrani, Nima Fotouhi, et al.
(författare)
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Coffee extract residue for production of ethanol and activated carbons
- 2015
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Ingår i: Journal of Cleaner Production. - : Elsevier BV. - 0959-6526 .- 1879-1786. ; 91, s. 64-70
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Tidskriftsartikel (refereegranskat)abstract
- Biomass as a waste product in the form coffee extract residue (CER) has been shown to have potential for the dual purpose of ethanol production and preparation of activated carbons. A straightforward method of direct hydrolysis and fermentation (DHF) is considered as the main option utilized in this study for the generation of fuel ethanol from the biomass waste. Factors such as loadings of saccharomyces cerevisiae, temperatures (21 and 30 degrees C) and substrate content were investigated to maximize the yield of ethanol. Ethanol production rates between 1.1 g and 0.70 g h(-1) kg(-1) without pretreatment and 2.7 and 23 g h(-1) kg(-1) dry substance with mild treatment were obtained, respectively. The CER was also used to prepare activated carbons using both chemical and physical activation methods. The effects of process parameters such as temperatures and concentrations of acid were varied and determined as to the yield, BET-surface areas and porosities of the final product. H3PO4 treatment at 600 degrees C and steam treatment at 700 degrees C show maximum surface area of >640 m(2) g(-1) with increased total pore and micropore volumes. (C) 2014 Elsevier Ltd. All rights reserved.
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| 20. |
- Younan, Diana, et al.
(författare)
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Ambient Temperature and Externalizing Behaviors of Adolescents in Southern California : A Longitudinal Analysis
- 2016
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Introduction: The climate-violence relationship has been debated for over 20 years, primarily because the supportive evidence was either ecological in nature or based on cross-sectional data. We conducted an individual-level, longitudinal analysis to investigate the association between temperature and externalizing behaviors in an urban-dwelling population.Methods: Participants (N=1287) of the Risk Factors for Antisocial Behavior Study, a multi-ethnic cohort of twins/triplets living in Southern California, were examined in 2000-2012 (aged 9 to 18 years) with repeated assessments of their aggressive and delinquent behaviors by the parent-reported Child Behavior Checklist. Ambient temperature was obtained from the local Meteorological Information System, with recordings from the closest site assigned to each geocoded residence. A monthly time-series from 1990 to 2012 was constructed and aggregated in 1-, 3-, and 6-month and 1-, 2-, and 3-year averages prior to each behavioral assessment. Multilevel mixed-effects models were used to estimate the effects of temperature, adjusting for within-family/within-individual correlations and other potential confounders.Results: Statistically significant associations (all p<0.05) were found between aggression and average temperature aggregated over 6 months or longer. Increasing aggressive behaviors were associated with rising 6-month average temperatures. However, longer-term (1- to 3-year average) temperatures showed a non-linear U-shaped association, with less aggressive behaviors at moderate temperatures (15-20°C), but increasing aggression at higher or lower temperatures. No significant effects were found on delinquency.Conclusions: Our study provides the first individual-level epidemiologic evidence supporting the adverse temperature effects on aggressive human behaviors. Similar approaches to studying violent crimes may further inform the scientific debates on climate changes and violence.
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| 21. |
- Younan, Diana, et al.
(författare)
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Environmental Determinants of Aggression in Adolescents : Role of Urban Neighborhood Greenspace
- 2016
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Ingår i: Journal of the American Academy of Child and Adolescent Psychiatry. - Amsterdam, Netherlands : Elsevier. - 0890-8567 .- 1527-5418. ; 55:7, s. 591-601
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Neighborhood greenspace improves mental health of urban-dwelling populations, but its putative neurobehavioral benefits in adolescents remain unclear. We conducted a prospective study on urban-dwelling adolescents to examine the association between greenspace in residential neighborhood and aggressive behaviors.Method: Participants (n = 1,287) of the Risk Factors for Antisocial Behavior Study, a multi-ethnic cohort of twins and triplets born in 1990 to 1995 and living in Southern California, were examined in 2000 to 2012 (aged 9-18 years) with repeated assessments of their aggressive behaviors by the parent-reported Child Behavior Checklist. Normalized Difference Vegetation Index (NDVI) derived from satellite imagery was used as a proxy for residential neighborhood greenspace aggregated over various spatiotemporal scales before each assessment. Multilevel mixed-effects models were used to estimate the effects of greenspace on aggressive behaviors, adjusting for within-family/within-individual correlations and other potential confounders.Results: Both short-term (1- to 6-month) and long-term (1- to 3-year) exposures to greenspace within 1,000 meters surrounding residences were associated with reduced aggressive behaviors. The benefit of increasing vegetation over the range (∼0.12 in NDVI) commonly seen in urban environments was equivalent to approximately 2 to 2.5 years of behavioral maturation. Sociodemographic factors (e.g., age, gender, race/ethnicity, and socioeconomic status) and neighborhood quality did not confound or modify these associations, and the benefits remained after accounting for temperature.Conclusion: Our novel findings support the benefits of neighborhood greenspace in reducing aggressive behaviors of urban-dwelling adolescents. Community-based interventions are needed to determine the efficacy of greenspace as a preemptive strategy to reduce aggressive behaviors in urban environments.
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| 22. |
- Younan, Diana, et al.
(författare)
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Long-Term Ambient Temperature and Externalizing Behaviors in Adolescents
- 2018
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Ingår i: American Journal of Epidemiology. - : Oxford University Press. - 0002-9262 .- 1476-6256. ; 187:9, s. 1931-1941
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Tidskriftsartikel (refereegranskat)abstract
- The climate-violence relationship has been debated for decades, and yet most of the supportive evidence came from ecological or cross-sectional analyses with very limited long-term exposure data. We conducted an individual-level, longitudinal study to investigate the association between ambient temperature and externalizing behaviors of urban-dwelling adolescents. Participants (n = 1,287) of the Risk Factors for Antisocial Behavior Study were examined in 2000-2012 (aged 9-18 years) with repeated assessments of their externalizing behaviors (aggression; delinquency). Ambient temperature data were obtained from the local Meteorological Information System. In adjusted multi-level models, aggressive behaviors significantly increased with rising average temperatures (per 1°C-increment) in preceding 1-3 years (β = 0.23, 95% CI: 0.00, 0.46; β = 0.35, 95% CI: 0.06, 0.63; β = 0.41, 95% CI: 0.08, 0.74; respectively), equivalent to 1.5-3 years of delay in age-related behavioral maturation. These associations were slightly stronger among girls and families of lower socioeconomic status, but greatly diminished in neighborhoods with higher greenspace. No significant associations were found with delinquency. Our study provides the first individual-level epidemiologic evidence supporting the adverse association of long-term ambient temperature and aggression. Similar approaches to studying meteorology and violent crimes may further inform scientific debates on climate change and collective violence.
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| 23. |
- Younan, Diana, et al.
(författare)
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Longitudinal Analysis of Particulate Air Pollutants and Adolescent Delinquent Behavior in Southern California
- 2018
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Ingår i: Journal of Abnormal Child Psychology. - New York, NY, USA : Springer. - 0091-0627 .- 1573-2835. ; 46:6, s. 1283-1293
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Tidskriftsartikel (refereegranskat)abstract
- Animal experiments and cross-sectional human studies have linked particulate matter (PM) with increased behavioral problems. We conducted a longitudinal study to examine whether the trajectories of delinquent behavior are affected by PM2.5 (PM with aerodynamic diameter ≤ 2.5 μm) exposures before and during adolescence. We used the parent-reported Child Behavior Checklist at age 9-18 with repeated measures every ~2-3 years (up to 4 behavioral assessments) on 682 children from the Risk Factors for Antisocial Behavior Study conducted in a multi-ethnic cohort of twins born in 1990-1995. Based on prospectively-collected residential addresses and a spatiotemporal model of ambient air concentrations in Southern California, monthly PM2.5 estimates were aggregated to represent long-term (1-, 2-, 3-year average) exposures preceding baseline and cumulative average exposure until the last assessment. Multilevel mixed-effects models were used to examine the association between PM2.5 exposure and individual trajectories of delinquent behavior, adjusting for within-family/within-individual correlations and potential confounders. We also examined whether psychosocial factors modified this association. The results sμggest that PM2.5 exposure at baseline and cumulative exposure during follow-up was significantly associated (p < 0.05) with increased delinquent behavior. The estimated effect sizes (per interquartile increase of PM2.5 by 3.12-5.18 μg/m3) were equivalent to the difference in delinquency scores between adolescents who are 3.5-4 years apart in age. The adverse effect was stronger in families with unfavorable parent-to-child relationships, increased parental stress or maternal depressive symptoms. Overall, these findings sμggest long-term PM2.5 exposure may increase delinquent behavior of urban-dwelling adolescents, with the resulting neurotoxic effect aggravated by psychosocial adversities.
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