| 1. |
- Fatima, Masoom, et al.
(författare)
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Low-Cost Single Chamber MFC Integrated With Novel Lignin-Based Carbon Fiber Felt Bioanode for Treatment of Recalcitrant Azo Dye
- 2021
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Ingår i: Frontiers in Energy Research. - : Frontiers Media SA. - 2296-598X. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- A flow through anaerobic microbial fuel cell (MFC) was designed and optimized for efficient treatment of recalcitrant textile wastewater. The membrane-less MFC was first time fabricated with a unique combination of electrodes, a novel bioanode of synthesized lignin-based electrospun carbon fiber supporting a biofilm of Geobacter sulfurreducens for acetate oxidation and an air-breathing cathode, consisting of a pyrolyzed macrocycle catalyst mixture on carbon bonded by polytetrafluoroethylene (PTFE). The effects of different organic loadings of acetate along with Acid Orange (AO5), operation time and ionic strength of auxiliary salts (conductivity enhancers) were investigated and responses in terms of polarization and degradation were studied. In addition, the decomposition of the organic species and the degradation of AO5 along with its metabolites and degraded products (2-aminobenzenesulfonic acid) were determined by chemical oxygen demand (COD) analysis, UV-Vis spectrophotometry and high-performance liquid chromatography (UV-HPLC) techniques. SEM and TEM images were also used to find out the biocompatibility of the microbes on lignin-based electrospun carbon felt anode and the morphology of the cathode. Reduction and breakage of the azo bond of AO5 occurs presumably as a side reaction, resulting in the formation of 2-aminobenzenesulfonic acid and unidentified aromatic amines. Maximum current density of anode 0.59 Am-2 and power density of 0.12 Wm(-2) were obtained under optimized conditions. As a result, decolouration of AO5 and chemical oxygen demand (COD) removal efficiency was 81 and 58%, respectively. These results revealed that the low-cost MFC assembly can offer significant potential for anaerobic decolouration of recalcitrant textile wastewater.
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| 2. |
- 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
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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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| 3. |
- Kiros, Yohannes, 1956-, et al.
(författare)
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Cobalt and cobalt-based macrocycle blacks as oxygen-reduction catalysts in alkaline fuel cells
- 1993
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Ingår i: Journal of Power Sources. - 0378-7753 .- 1873-2755. ; 45:2, s. 219-227
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Tidskriftsartikel (refereegranskat)abstract
- The electrochemical reduction of oxygen on high surface are carbons catalyzed by cobalt and pyrolyzed macrocycles has been studied in alkaline fuel cells. Tests were also carried out with 'green black', i.e., pyrolyzed phyto-biomass. Galvanostatic polarization curves show that cobalt from cobalt acetate and fine cobalt metal power exhibit a high catalytic activity. The activity of pyrolyzed cobalt tetraphenylporphyrin (CoTPP) is due to the combined effects of the cobalt additive and the charred residue of the macrocycle. 'Green black', with chlorophyll as macrocycle black precursor, has a similar effect. The dissolution of cobalt from the electrode surface has been established. Life tests with these electrodes are reported. © 1993.
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| 4. |
- Kiros, Yohannes, 1956-
(författare)
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Electrocatalytic properties of Co, Pt, and Pt-Co on carbon for the reduction of oxygen in alkaline fuel cells
- 1996
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Ingår i: Journal of the Electrochemical Society. - : Electrochemical Society. - 0013-4651 .- 1945-7111. ; 143:7, s. 2152-2157
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Tidskriftsartikel (refereegranskat)abstract
- The effect of cobalt, platinum, and cobalt-platinum, alloys on high surface area carbons for oxygen reduction in alkaline electrolyte was investigated. The Pt-Co catalyst with ca. 1:3 atomic ratio was prepared by addition of H2PtCl6 solution to a mixture of methanol and a 5% surfactant in deionized water containing cobalt acetate and carbon suspension. This was followed by drying and heat-treatment at 700 and 900°C in a flow of hydrogen and nitrogen gas mixtures. Polarization curves and kinetic parameters for Pt, Co, and Pt-Co were conducted and compared in 6 M KOH and at 80°C. Higher activities were observed for the Pt-Co alloy, that had been heat treated at 900°C. In addition to increased activity of this catalyst, the unalloyed base metal (Co) contributes to total performance improvement of the oxygen reduction process. Furthermore, surface, structural, and chemical characterizations of the catalysts were carried out using transmission electron microscopy, x-ray diffraction, Brunauer, Emmett, and Teller method, and atomic absorption spectroscopy. Dissolution of cobalt from the electrodes, both from the single cobalt phase and Pt-Co alloy catalysts, has been established. The x-ray results demonstrated a shift to lower lattice parameters (3.618 Å) by the Pt-Co alloys, prepared at 900°C, than the pure platinum catalyst (3.919 Å).
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| 5. |
- Kiros, Yohannes, 1956-, et al.
(författare)
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Electrode R&D, stack design and performance of biomass-based alkaline fuel cell module
- 1999
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Ingår i: International journal of hydrogen energy. - : Pergamon Press. - 0360-3199 .- 1879-3487. ; 24, s. 549-564
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Tidskriftsartikel (refereegranskat)abstract
- Electrode formulations with di}erent materials and manufacturing techniques were tested electrochemically in order to assess their stability and activity in long!term operations. Cathode electrocatalysts such as CoTPP, Ca0.9La0.1MnO3 and Pt-Co alloys were incorporated in high surface area carbons and operated at a constant load of 100 mA cm-2 80C and an electrolyte concentration of 6M KOH. Similarly, anode catalysts with Pt-Pd bimetallic combinations were also tested and ascertained in half!cell measurements. Surface area measurements and Transmission Electron Microscopy (TEM) analyses were carried out both before and after the electrochemical test procedures. The electrodes were incorporated into a seven and two cell module design of the external and internal manifolding types and the experiences gained from these design principles are described, respectively. Furthermore, a biomass fed AFC module with all the system descriptions, steps, and a demonstration layout of producer gas to alkaline fuel cell are examined and discussed. Wood charcoal and agro-residues were used as feedstock and as a primary fuel. Power output of the different feedstock in a producer gas fed alkaline fuel cell has the shown potentiality and effciency to be applied as a stand alone power generator.
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| 6. |
- Kiros, Yohannes, 1956-, et al.
(författare)
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Gas diffusion electrode
- 2012
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Patent (populärvet., debatt m.m.)abstract
- A method of preparing a gas diffusion electrode comprising a diffusion layer, and a reaction layer arranged to eachother, wherein the diffusion layer is prepared by i) admixing a) sacrificial material, b) polymer and c) a metal - based material and d)optional further components, wherein the sacrificial material has a release temperature below about 275 °C and is added in anamount from about 1 to about 25 wt% based on the total weight of components a) -d) admixed; ii) forming a diffusion layer from theadmixture of step i); iii) heating the forming diffusion layer to a temperature lower than about 275 °C so as to release at least a partof said sacrificial material from the diffusion layer. A gas diffusion electrode comprising a diffusion layer and a reaction layer ar -ranged to one another, wherein the diffusion layer has a porosity ranging from about 60 to about 95 %, and an electrolytic cell comprising the electrode. An electrolytic cell, a fuel cell comprising the gas diffusion electrode and a metal-air battery comprising thegas diffusion electrode.
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| 7. |
- Kiros, Yohannes, 1956-
(författare)
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Oxygen reduction electrode
- 2002
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Patent (populärvet., debatt m.m.)abstract
- The invention refers to an oxygen reduction electrode comprising at least three layers: a current collector, a diffusion layer comprising at least PTFE; and a catalytical active layer comprising at least a mixture of perovskites and pyrolysed macrocycles. In this way, oxygen may be utilised from air without an initial removal of carbon dioxide. Moreover, the invention refers to methods for preparing the electrode, as well as fuel cells and other products wherein the electrode can be used.
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| 8. |
- Kiros, Yohannes, 1956-, et al.
(författare)
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Pyrolyzed macrocycles on high surface area carbons for the reduction of oxygen in alkaline fuel cells
- 1991
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Ingår i: Journal of Power Sources. - 0378-7753 .- 1873-2755. ; 36:4, s. 547-555
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Tidskriftsartikel (refereegranskat)abstract
- Polarization characteristics and preparation methods of double-layer porous gas diffusion electrodes on various carbon materials in alkaline fuel cells were investigated. The electrodes with active carbon carriers were catalyzed with cobalt/iron tetraphonylporphyrin or silver. These electrodes show a potential of - 186 mV (versus Hg/HgO) at 1.0 A/cm2 when operated with oxygen at 40 °C and 5 M KOH. Various techniques such as surface area measurements, scanning (SEM) and transmission (TEM) electron microscopy in combination with energy dispersive spectroscopy (EDS) and electron energy loss spectroscopy (EELS) were used to characterize the structure and morphology of the catalyst layer.
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| 9. |
- Li, Zhuofeng, 1991-, et al.
(författare)
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Tuning morphology, composition and oxygen reduction reaction (ORR) catalytic performance of manganese oxide particles fabricated by γ-radiation induced synthesis
- 2021
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 583, s. 71-79
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Tidskriftsartikel (refereegranskat)abstract
- A γ-radiation induced synthesis method is used to fabricate manganese oxide catalysts through both reduction and oxidation routes. It is shown that the morphology, composition and electrochemical performance of the produced manganese oxide particles can be tuned by altering the redox conditions. The catalysts prepared via radiolytic oxidation have a hollow spherical morphology, possess γ-MnO2 structure and show high catalytic activity for the complete four-electron reaction pathway of the oxygen reduction reaction (ORR) in alkaline electrolyte. Meanwhile, the catalysts synthesized via radiolytic reduction possess a rod-like morphology with a Mn3O4 bulk structure and favour the incomplete two-electron reaction pathway for ORR. The high catalytic activity of the manganese oxide synthesized via the oxidation route can be attributed to high electrochemical surface area and increased amount of Mn3+ on the surface as compared to those in the sample obtained via the reduction route.
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| 10. |
- 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
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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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