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Papaderakis AA, Ejigu A, Yang J, Elgendy A, Radha B, Keerthi A, Juel A, Dryfe RAW. Anion Intercalation into Graphite Drives Surface Wetting. J Am Chem Soc 2023; 145:8007-8020. [PMID: 36977204 PMCID: PMC10103168 DOI: 10.1021/jacs.2c13630] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/30/2023]
Abstract
The unique layered structure of graphite with its tunable interlayer distance establishes almost ideal conditions for the accommodation of ions into its structure. The smooth and chemically inert nature of the graphite surface also means that it is an ideal substrate for electrowetting. Here, we combine these two unique properties of this material by demonstrating the significant effect of anion intercalation on the electrowetting response of graphitic surfaces in contact with concentrated aqueous and organic electrolytes as well as ionic liquids. The structural changes during intercalation/deintercalation were probed using in situ Raman spectroscopy, and the results were used to provide insights into the influence of intercalation staging on the rate and reversibility of electrowetting. We show, by tuning the size of the intercalant and the stage of intercalation, that a fully reversible electrowetting response can be attained. The approach is extended to the development of biphasic (oil/water) systems that exhibit a fully reproducible electrowetting response with a near-zero voltage threshold and unprecedented contact angle variations of more than 120° within a potential window of less than 2 V.
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Affiliation(s)
- Athanasios A Papaderakis
- Department of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, U. K
- Henry Royce Institute, University of Manchester, Oxford Road, Manchester M13 9PL, U. K
| | - Andinet Ejigu
- Department of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, U. K
- Henry Royce Institute, University of Manchester, Oxford Road, Manchester M13 9PL, U. K
| | - Jing Yang
- Department of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, U. K
- Henry Royce Institute, University of Manchester, Oxford Road, Manchester M13 9PL, U. K
| | - Amr Elgendy
- Department of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, U. K
- Henry Royce Institute, University of Manchester, Oxford Road, Manchester M13 9PL, U. K
- Egyptian Petroleum Research Institute, 11727 Cairo, Egypt
| | - Boya Radha
- Department of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, U. K
- National Graphene Institute, University of Manchester, Oxford Road, Manchester M13 9PL, U. K
| | - Ashok Keerthi
- Department of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, U. K
- National Graphene Institute, University of Manchester, Oxford Road, Manchester M13 9PL, U. K
| | - Anne Juel
- Department of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, U. K
| | - Robert A W Dryfe
- Department of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, U. K
- Henry Royce Institute, University of Manchester, Oxford Road, Manchester M13 9PL, U. K
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Jones AE, Ejigu A, Wang B, Adams RW, Bissett MA, Dryfe RA. Quinone voltammetry for redox-flow battery applications. J Electroanal Chem (Lausanne) 2022. [DOI: 10.1016/j.jelechem.2022.116572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Ejigu A, Le Fevre LW, Elgendy A, Spencer BF, Bawn C, Dryfe RAW. Optimization of Electrolytes for High-Performance Aqueous Aluminum-Ion Batteries. ACS Appl Mater Interfaces 2022; 14:25232-25245. [PMID: 35622978 PMCID: PMC9185688 DOI: 10.1021/acsami.1c23278] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Aqueous rechargeable batteries based on aluminum chemistry have become the focus of immense research interest owing to their earth abundance, low cost, and the higher theoretical volumetric energy density of this element compared to lithium-ion batteries. Efforts to harness this huge potential have been hindered by the narrow potential window of water and by passivating effects of the high-electrical band-gap aluminum oxide film. Herein, we report a high-performing aqueous aluminum-ion battery (AIB), which is constructed using a Zn-supported Al alloy, an aluminum bis(trifluoromethanesulfonyl)imide (Al[TFSI]3) electrolyte, and a MnO2 cathode. The use of Al[TFSI]3 significantly extends the voltage window of the electrolyte and enables the cell to access Al3+/Al electrochemistry, while the use of Zn-Al alloy mitigates the issue of surface passivation. The Zn-Al alloy, which is produced by in situ electrochemical deposition, obtained from Al[TFSI]3 showed excellent long-term reversibility for Al electrochemistry and displays the highest performance in AIB when compared to the response obtained in Al2(SO4)3 or aluminum trifluoromethanesulfonate electrolyte. AIB cells constructed using the Zn-Al|Al[TFSI]3|MnO2 combination achieved a record discharge voltage plateau of 1.75 V and a specific capacity of 450 mAh g-1 without significant capacity fade after 400 cycles. These findings will promote the development of energy-dense aqueous AIBs.
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Affiliation(s)
- Andinet Ejigu
- Dept.
of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
- Henry
Royce Institute, University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
| | - Lewis W. Le Fevre
- Henry
Royce Institute, University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
| | - Amr Elgendy
- Dept.
of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
- Henry
Royce Institute, University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
| | - Ben F. Spencer
- Dept.
of Materials, University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
| | - Carlo Bawn
- Dept.
of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
| | - Robert A. W. Dryfe
- Dept.
of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
- Henry
Royce Institute, University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
- . Tel: +44 (0)161-306-4522. Fax: +44 (0)161-275-4598
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Ejigu A, Le Fevre LW, Dryfe RAW. Reversible Electrochemical Energy Storage Based on Zinc-Halide Chemistry. ACS Appl Mater Interfaces 2021; 13:14112-14121. [PMID: 33724772 PMCID: PMC8041251 DOI: 10.1021/acsami.0c20622] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Accepted: 02/23/2021] [Indexed: 05/23/2023]
Abstract
The development of rechargeable Zinc-ion batteries (ZIBs) has been hindered by the lack of efficient cathode materials due to the strong binding of divalent zinc ions with the host lattice. Herein, we report a strategy that eliminates the participation of Zn2+ within the cathode chemistry. The approach involves the use of composite cathode materials that contain Zn halides (ZnCl2, ZnBr2, and ZnI2) and carbon (graphite or activated carbon), where the halide ions act both as charge carriers and redox centers while using a Zn2+-conducting water-in-salt gel electrolyte. The use of graphite in the composite electrode produced batterylike behavior, where the voltage plateau was related to the standard potential of the halogen species. When activated carbon was used in the composite, however, the cell acted as a hybrid Zn-ion capacitor due to the fast, reversible halide ion electrosorption/desorption in the carbon pores. The ZnX2-activated carbon composite delivers a capacity of over 400 mAh g-1 and cell energy density of 140 Wh kg-1 while retaining over 95% of its capacity after 500 cycles. The halogen reaction mechanism has been elucidated using combinations of electrochemical and in situ spectroscopic techniques.
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Affiliation(s)
- Andinet Ejigu
- Department
of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
- National
Graphene Institute, University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
| | - Lewis W. Le Fevre
- National
Graphene Institute, University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
- Department
of Electrical and Electronic Engineering, University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
| | - Robert A. W. Dryfe
- Department
of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
- National
Graphene Institute, University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
- Henry
Royce Institute, University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
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Le Fevre LW, Ejigu A, Todd R, Forsyth AJ, Dryfe RAW. High temperature supercapacitors using water-in-salt electrolytes: stability above 100 °C. Chem Commun (Camb) 2021; 57:5294-5297. [PMID: 33942833 DOI: 10.1039/d1cc01087e] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The high temperature performance of water-in-salt electrolytes was investigated using a carbon-based electrode with commercial cell components. Supercapacitors using 21 m Li bis(trifluoromethylsulphonyl)imide (TFSI) and 21 m LiTFSI + 7 m Li trifluoromethanesulphonyl electrolytes are shown to operate at a voltage of 2 V at 100 °C and 120 °C, respectively, with gravimetric capacitances exceeding 100 F g-1.
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Affiliation(s)
- Lewis W Le Fevre
- Department of Electrical and Electronic Engineering, The University of Manchester, Manchester, M13 9PL, UK and Department of Chemistry, The University of Manchester, Manchester, M13 9PL, UK. and National Graphene Institute, The University of Manchester, Manchester, M13 9PL, UK
| | - Andinet Ejigu
- Department of Chemistry, The University of Manchester, Manchester, M13 9PL, UK. and National Graphene Institute, The University of Manchester, Manchester, M13 9PL, UK
| | - Rebecca Todd
- Department of Electrical and Electronic Engineering, The University of Manchester, Manchester, M13 9PL, UK
| | - Andrew J Forsyth
- Department of Electrical and Electronic Engineering, The University of Manchester, Manchester, M13 9PL, UK
| | - Robert A W Dryfe
- Department of Chemistry, The University of Manchester, Manchester, M13 9PL, UK. and National Graphene Institute, The University of Manchester, Manchester, M13 9PL, UK
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Iamprasertkun P, Ejigu A, Dryfe RAW. Understanding the electrochemistry of "water-in-salt" electrolytes: basal plane highly ordered pyrolytic graphite as a model system. Chem Sci 2020; 11:6978-6989. [PMID: 34122994 PMCID: PMC8159404 DOI: 10.1039/d0sc01754j] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Accepted: 06/05/2020] [Indexed: 12/21/2022] Open
Abstract
A new approach to expand the accessible voltage window of electrochemical energy storage systems, based on so-called "water-in-salt" electrolytes, has been expounded recently. Although studies of transport in concentrated electrolytes date back over several decades, the recent demonstration that concentrated aqueous electrolyte systems can be used in the lithium ion battery context has rekindled interest in the electrochemical properties of highly concentrated aqueous electrolytes. The original aqueous lithium ion battery conception was based on the use of concentrated solutions of lithium bis(trifluoromethanesulfonyl)imide, although these electrolytes still possess some drawbacks including cost, toxicity, and safety. In this work we describe the electrochemical behavior of a simple 1 : 1 electrolyte based on highly concentrated aqueous solutions of potassium fluoride (KF). Highly ordered pyrolytic graphite (HOPG) is used as well-defined model carbon to study the electrochemical properties of the electrolyte, as well as its basal plane capacitance, from a microscopic perspective: the KF electrolyte exhibits an unusually wide potential window (up to 2.6 V). The faradaic response on HOPG is also reported using K3Fe(CN)6 as a model redox probe: the highly concentrated electrolyte provides good electrochemical reversibility and protects the HOPG surface from adsorption of contaminants. Moreover, this electrolyte was applied to symmetrical supercapacitors (using graphene and activated carbon as active materials) in order to quantify its performance in energy storage applications. It is found that the activated carbon and graphene supercapacitors demonstrate high gravimetric capacitance (221 F g-1 for activated carbon, and 56 F g-1 for graphene), a stable working voltage window of 2.0 V, which is significantly higher than the usual range of water-based capacitors, and excellent stability over 10 000 cycles. These results provide fundamental insight into the wider applicability of highly concentrated electrolytes, which should enable their application in future of energy storage technologies.
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Affiliation(s)
- Pawin Iamprasertkun
- Department of Chemistry, University of Manchester Oxford Road Manchester M13 9PL UK +44 (0)161-275-4598
- National Graphene Institute, University of Manchester Oxford Road M13 9PL UK
| | - Andinet Ejigu
- Department of Chemistry, University of Manchester Oxford Road Manchester M13 9PL UK +44 (0)161-275-4598
- National Graphene Institute, University of Manchester Oxford Road M13 9PL UK
| | - Robert A W Dryfe
- Department of Chemistry, University of Manchester Oxford Road Manchester M13 9PL UK +44 (0)161-275-4598
- National Graphene Institute, University of Manchester Oxford Road M13 9PL UK
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Ejigu A, Le Fevre LW, Fujisawa K, Terrones M, Forsyth AJ, Dryfe RAW. Electrochemically Exfoliated Graphene Electrode for High-Performance Rechargeable Chloroaluminate and Dual-Ion Batteries. ACS Appl Mater Interfaces 2019; 11:23261-23270. [PMID: 31252480 DOI: 10.1021/acsami.9b06528] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The current state-of-the-art positive electrode material for chloroaluminate ion batteries (AIBs) or dual-ion batteries (DIBs) is highly crystalline graphite; however, the rate capability of this material at high discharge currents is significantly reduced by the modest conductivity of graphite. This limitation is addressed through the use of graphene-based positive electrodes, which can improve the rate capability of these batteries due to their higher conductivity. However, conventional methods of graphene production induce a significant number of defects, which impair the performance of AIBs and DIBs. Herein, we report the use of a defect-free graphene positive electrode, which was produced using the electrochemical exfoliation of graphite in an aqueous solution with the aid of Co2+ as an antioxidant. The Co-treated graphene electrode achieved high capacities of 150 mAh g-1 in DIBs and 130 mAh g-1 in AIBs with high rate capability for both batteries. The charge-discharge mechanism of the batteries is examined using in situ Raman spectroscopy, and the results revealed that the intercalation density of [AlCl4]- or [PF6]- increased from a dilute staging index graphite intercalation compound (GIC) to a stage 1 GIC within the operating voltage window. The simple production method of high-quality graphene in conjunction with its high performance in DIBs should enable the use of graphene for DIB technologies.
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Affiliation(s)
| | | | - Kazunori Fujisawa
- Department of Physics, Center for Two-Dimensional and Layered Materials and Center for Atomically Thin Multifunctional Coatings (ATOMIC) , The Pennsylvania State University , University Park , Pennsylvania 16802 , United States
| | - Mauricio Terrones
- Department of Physics, Center for Two-Dimensional and Layered Materials and Center for Atomically Thin Multifunctional Coatings (ATOMIC) , The Pennsylvania State University , University Park , Pennsylvania 16802 , United States
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Eshtaya M, Ejigu A, Stephens G, Walsh DA, Chen GZ, Croft AK. Developing energy efficient lignin biomass processing - towards understanding mediator behaviour in ionic liquids. Faraday Discuss 2018; 190:127-45. [PMID: 27228384 DOI: 10.1039/c5fd00226e] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Environmental concerns have brought attention to the requirement for more efficient and renewable processes for chemicals production. Lignin is the second most abundant natural polymer, and might serve as a sustainable resource for manufacturing fuels and aromatic derivatives for the chemicals industry after being depolymerised. In this work, the mediator 2,2'-azino-bis(3-ethylbenthiazoline-6-sulfonic acid) diammonium salt (ABTS), commonly used with enzyme degradation systems, has been evaluated by means of cyclic voltammetry (CV) for enhancing the oxidation of the non-phenolic lignin model compound veratryl alcohol and three types of lignin (organosolv, Kraft and lignosulfonate) in the ionic liquid 1-ethyl-3-methylimidazolium ethyl sulfate, ([C2mim][C2SO4]). The presence of either veratryl alcohol or organosolv lignin increased the second oxidation peak of ABTS under select conditions, indicating the ABTS-mediated oxidation of these molecules at high potentials in [C2mim][C2SO4]. Furthermore, CV was applied as a quick and efficient way to explore the impact of water in the ABTS-mediated oxidation of both organosolv and lignosulfonate lignin. Higher catalytic efficiencies of ABTS were observed for lignosulfonate solutions either in sodium acetate buffer or when [C2mim][C2SO4] (15 v/v%) was present in the buffer solution, whilst there was no change found in the catalytic efficiency of ABTS in [C2mim][C2SO4]-lignosulfonate mixtures relative to ABTS alone. In contrast, organosolv showed an initial increase in oxidation, followed by a significant decrease on increasing the water content of a [C2mim][C2SO4] solution.
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Affiliation(s)
- Majd Eshtaya
- Department of Chemical and Environmental Engineering, Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD, UK.
| | - Andinet Ejigu
- Department of Chemistry, University of Nottingham, Nottingham NG7 2RD, UK
| | - Gill Stephens
- Department of Chemical and Environmental Engineering, Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD, UK.
| | - Darren A Walsh
- Department of Chemistry, University of Nottingham, Nottingham NG7 2RD, UK
| | - George Z Chen
- Department of Chemical and Environmental Engineering, Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD, UK. and Department of Chemical and Environmental Engineering, Faculty of Science & Engineering, University of Nottingham Ningbo China, Ningbo 315100, P. R. China
| | - Anna K Croft
- Department of Chemical and Environmental Engineering, Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD, UK.
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Ejigu A, Kinloch IA, Dryfe RAW. Single Stage Simultaneous Electrochemical Exfoliation and Functionalization of Graphene. ACS Appl Mater Interfaces 2017; 9:710-721. [PMID: 27936538 DOI: 10.1021/acsami.6b12868] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/14/2023]
Abstract
Development of applications for graphene are currently hampered by its poor dispersion in common, low boiling point solvents. Covalent functionalization is considered as one method for addressing this challenge. To date, approaches have tended to focus upon producing the graphene and functionalizing subsequently. Herein, we describe simultaneous electrochemical exfoliation and functionalization of graphite using diazonium salts at a single applied potential for the first time. Such an approach is advantageous, compared to postfunctionalization of premade graphene, as both functionalization and exfoliation occur at the same time, meaning that monolayer or few-layer graphene can be functionalized and stabilized in situ before they aggregate. Furthermore, the N2 generated during in situ diazonium reduction is found to aid the separation of functionalized graphene sheets. The degree of graphene functionalization was controlled by varying the concentration of the diazonium species in the exfoliation solution. The formation of functionalized graphene was confirmed using Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. The functionalized graphene was soluble in aqueous systems, and its solubility was 2 orders of magnitude higher than the nonfunctionalized electrochemically exfoliated graphene sheets. Moreover, the functionalization enhanced the charge storage capacity when used as an electrode in supercapacitor devices with the specific capacitance being highly dependent on the degree of graphene functionalization. This simple method of in situ simultaneous exfoliation and functionaliztion may aid the processing of graphene for various applications.
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Affiliation(s)
- Andinet Ejigu
- School of Chemistry, ‡School of Materials, and §National Graphene Institute, University of Manchester , Oxford Road, Manchester M13 9PL, U.K
| | - Ian A Kinloch
- School of Chemistry, ‡School of Materials, and §National Graphene Institute, University of Manchester , Oxford Road, Manchester M13 9PL, U.K
| | - Robert A W Dryfe
- School of Chemistry, ‡School of Materials, and §National Graphene Institute, University of Manchester , Oxford Road, Manchester M13 9PL, U.K
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Affiliation(s)
- Andinet Ejigu
- School
of Chemistry, The University of Nottingham, Nottingham NG7 2RD, United Kingdom
| | - Matthew Edwards
- School
of Chemistry, The University of Nottingham, Nottingham NG7 2RD, United Kingdom
| | - Darren A. Walsh
- School
of Chemistry, The University of Nottingham, Nottingham NG7 2RD, United Kingdom
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Walsh DA, Ejigu A, Muhammad S, Licence P. The Formation and Role of Oxide Layers on Pt during Hydrazine Oxidation in Protic Ionic Liquids. ChemElectroChem 2013. [DOI: 10.1002/celc.201300111] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Walsh DA, Ejigu A, Smith J, Licence P. Kinetics and mechanism of oxygen reduction in a protic ionic liquid. Phys Chem Chem Phys 2013; 15:7548-54. [DOI: 10.1039/c3cp44669g] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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Ejigu A, Johnson L, Licence P, Walsh DA. Electrocatalytic oxidation of methanol and carbon monoxide at platinum in protic ionic liquids. Electrochem commun 2012. [DOI: 10.1016/j.elecom.2012.07.020] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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Ejigu A, Lovelock KR, Licence P, Walsh DA. Iodide/triiodide electrochemistry in ionic liquids: Effect of viscosity on mass transport, voltammetry and scanning electrochemical microscopy. Electrochim Acta 2011. [DOI: 10.1016/j.electacta.2011.03.108] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Lovelock KRJ, Ejigu A, Loh SF, Men S, Licence P, Walsh DA. On the diffusion of ferrocenemethanol in room-temperature ionic liquids: an electrochemical study. Phys Chem Chem Phys 2011; 13:10155-64. [PMID: 21526252 DOI: 10.1039/c1cp20392d] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The electrochemical behaviour of ferrocenemethanol (FcMeOH) has been studied in a range of room-temperature ionic liquids (RTILs) using cyclic voltammetry, chronoamperomery and scanning electrochemical microscopy (SECM). The diffusion coefficient of FcMeOH, measured using chronoamperometry, decreased with increasing RTIL viscosity. Analysis of the mass transport properties of the RTILs revealed that the Stokes-Einstein equation did not apply to our data. The "correlation length" was estimated from diffusion coefficient data and corresponded well to the average size of holes (voids) in the liquid, suggesting that a model in which the diffusing species jumps between holes in the liquid is appropriate in these liquids. Cyclic voltammetry at ultramicroelectrodes demonstrated that the ability to record steady-state voltammograms during ferrocenemethanol oxidation depended on the voltammetric scan rate, the electrode dimensions and the RTIL viscosity. Similarly, the ability to record steady-state SECM feedback approach curves depended on the RTIL viscosity, the SECM tip radius and the tip approach speed. Using 1.3 μm Pt SECM tips, steady-state SECM feedback approach curves were obtained in RTILs, provided that the tip approach speed was low enough to maintain steady-state diffusion at the SECM tip. In the case where tip-induced convection contributed significantly to the SECM tip current, this effect could be accounted for theoretically using mass transport equations that include diffusive and convective terms. Finally, the rate of heterogeneous electron transfer across the electrode/RTIL interface during ferrocenemethanol oxidation was estimated using SECM, and k(0) was at least 0.1 cm s(-1) in one of the least viscous RTILs studied.
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Affiliation(s)
- Kevin R J Lovelock
- School of Chemistry, The University of Nottingham, Nottingham, NG7 2RD, UK
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Ejigu A, Taye M, Zenebe G, Mamo G. Locked-in syndrome (LIS). Ethiop Med J 1995; 33:59-62. [PMID: 7895747] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Two young female patients, who were admitted to Tikur Anbessa Hospital in September 1993 and January 1994, respectively, with locked-in syndrome are reported and literature is reviewed.
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Affiliation(s)
- A Ejigu
- Department of Internal Medicine, Faculty of Medicine, Addis Abeba University
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Ejigu A. Intracranial tuberculosis mimicking brain tumour: case report. East Afr Med J 1993; 70:659-660. [PMID: 8187665] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
A 49-year-old male patient with an intracranial tuberculoma who presented with motor aphasia and right sided hemiplegia is discussed. Although tuberculosis is common in the country, to date antemortem histologically confirmed case has not been reported in Ethiopia. It is recommended that intracranial tuberculoma should be considered in the differential diagnosis of central nervous system mass lesions.
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Affiliation(s)
- A Ejigu
- Department of Internal Medicine, Faculty of Medicine, Addis Ababa University, Ethiopia
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