Publications by authors named "David Aili"

8 Publications

  • Page 1 of 1

Studies on Anion Exchange Membrane and Interface Properties by Electrochemical Impedance Spectroscopy: The Role of pH.

Membranes (Basel) 2021 Oct 10;11(10). Epub 2021 Oct 10.

State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150090, China.

Ion-exchange membranes (IEMs) represent a key component in various electrochemical energy conversion and storage systems. In this study, electrochemical impedance spectroscopy (EIS) was used to investigate the effects of structural changes of anion exchange membranes (AEMs) on the bulk membrane and interface properties as a function of solution pH. The variations in the physico/electrochemical properties, including ion exchange capacity, swelling degree, fixed charge density, zeta potentials as well as membrane and interface resistances of two commercial AEMs and cation exchange membranes (CEMs, as a control) were systematically investigated in different pH environments. Structural changes of the membrane surface were analyzed by Fourier transform infrared and X-ray photoelectron spectroscopy. Most notably, at high pH (pH > 10), the membrane (R) and the diffusion boundary layer resistances (R) increased for the two AEMs, whereas the electrical double layer resistance decreased simultaneously. This increase in R and R was mainly attributed to the deprotonation of the tertiary amino groups (-NRH) as a membrane functionality. Our results show that the local pH at the membrane-solution interface plays a crucial role on membrane electrochemical properties in IEM transport processes, particularly for AEMs.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/membranes11100771DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8540937PMC
October 2021

Electroreduction of COto ethanol by electrochemically deposited Cu-lignin complexes on Ni foam electrodes.

Nanotechnology 2021 Nov 12;33(5). Epub 2021 Nov 12.

Department of Chemical Engineering, Indian Institute of Technology Delhi, New Delhi 110016, India.

A low cost, non-toxic and highly selective catalyst based on a Cu-lignin molecular complex is developed for COelectroreduction to ethanol. Ni foam (NF), Cu-Ni foam (Cu-NF) and Cu-lignin-Ni foam (Cu-lignin-NF) were prepared by a facile and reproducible electrochemical deposition method. The electrochemical COreduction activity of Cu-lignin-NF was found to be higher than Cu-NF. A maximum faradaic efficiency of 23.2% with current density of 22.5 mA cmwas obtained for Cu-lignin-NF at -0.80 V (versus RHE) in 0.1 M NaSOtowards ethanol production. The enhancement of catalytic performance is attributed to the growth of the number of active sites and the change of oxidation states of Cu and NF due to the presence of lignin.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1088/1361-6528/ac302bDOI Listing
November 2021

Insights and Challenges for Applying Bipolar Membranes in Advanced Electrochemical Energy Systems.

ACS Energy Lett 2021 Jul 23;6(7):2539-2548. Epub 2021 Jun 23.

Department of Chemical Engineering, Delft University of Technology, 2629 HZ Delft, The Netherlands.

Bipolar membranes (BPMs) are gaining interest in energy conversion technologies. These membranes are composed of cation- and anion-exchange layers, with an interfacial layer in between. This gives the freedom to operate in different conditions (pH, concentration, composition) at both sides. Such membranes are used in two operational modes, forward and reverse bias. BPMs have been implemented in various electrochemical applications, like water and CO electrolyzers, fuel cells, and flow batteries, while BPMs are historically designed for acid/base production. Therefore, current commercial BPMs are not optimized, as the conditions change per application. Although the ideal BPM has highly conductive layers, high water dissociation kinetics, long lifetime, and low ion crossover, each application has its own priorities to be competitive in its field. We describe the challenges and requirements for future BPMs, and identify existing developments that can be leveraged to develop BPMs toward the scale of practical applications.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acsenergylett.1c00618DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8276271PMC
July 2021

Advancement toward Polymer Electrolyte Membrane Fuel Cells at Elevated Temperatures.

Research (Wash D C) 2020 8;2020:9089405. Epub 2020 Jun 8.

Fuels and Energy Technology Institute & WA School of Mines: Minerals, Energy and Chemical Engineering, Curtin University, WA6102, Perth, Australia.

Elevation of operational temperatures of polymer electrolyte membrane fuel cells (PEMFCs) has been demonstrated with phosphoric acid-doped polybenzimidazole (PA/PBI) membranes. The technical perspective of the technology is simplified construction and operation with possible integration with, e.g., methanol reformers. Toward this target, significant efforts have been made to develop acid-base polymer membranes, inorganic proton conductors, and organic-inorganic composite materials. This report is devoted to updating the recent progress of the development particularly of acid-doped PBI, phosphate-based solid inorganic proton conductors, and their composite electrolytes. Long-term stability of PBI membranes has been well documented, however, at typical temperatures of 160°C. Inorganic proton-conducting materials, e.g., alkali metal dihydrogen phosphates, heteropolyacids, tetravalent metal pyrophosphates, and phosphosilicates, exhibit significant proton conductivity at temperatures of up to 300°C but have so far found limited applications in the form of thin films. Composite membranes of PBI and phosphates, particularly formed phosphosilicates in the polymer matrix, showed exceptionally stable conductivity at temperatures well above 200°C. Fuel cell tests at up to 260°C are reported operational with good tolerance of up to 16% CO in hydrogen, fast kinetics for direct methanol oxidation, and feasibility of nonprecious metal catalysts. The prospect and future exploration of new proton conductors based on phosphate immobilization and fuel cell technologies at temperatures above 200°C are discussed.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.34133/2020/9089405DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7298353PMC
June 2020

Design of Monovalent Ion Selective Membranes for Reducing the Impacts of Multivalent Ions in Reverse Electrodialysis.

Membranes (Basel) 2019 Dec 31;10(1). Epub 2019 Dec 31.

Department of Energy Conversion and Storage, Technical University of Denmark, Building 310, 2800 Kgs. Lyngby, Denmark.

Reverse electrodialysis (RED) represents one of the most promising membrane-based technologies for clean and renewable energy production from mixing water solutions. However, the presence of multivalent ions in natural water drastically reduces system performance, in particular, the open-circuit voltage (OCV) and the output power. This effect is largely described by the "uphill transport" phenomenon, in which multivalent ions are transported against the concentration gradient. In this work, recent advances in the investigation of the impact of multivalent ions on power generation by RED are systematically reviewed along with possible strategies to overcome this challenge. In particular, the use of monovalent ion-selective membranes represents a promising alternative to reduce the negative impact of multivalent ions given the availability of low-cost materials and an easy route of membrane synthesis. A thorough assessment of the materials and methodologies used to prepare monovalent selective ion exchange membranes (both cation and anion exchange membranes) for applications in (reverse) electrodialysis is performed. Moreover, transport mechanisms under conditions of extreme salinity gradient are analyzed and compared for a better understanding of the design criteria. The ultimate goal of the present work is to propose a prospective research direction on the development of new membrane materials for effective implementation of RED under natural feed conditions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/membranes10010007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7022468PMC
December 2019

Ion-Exchange-Induced Selective Etching for the Synthesis of Amino-Functionalized Hollow Mesoporous Silica for Elevated-High-Temperature Fuel Cells.

ACS Appl Mater Interfaces 2017 Sep 7;9(37):31922-31930. Epub 2017 Sep 7.

Fuels and Energy Technology Institute & Department of Chemical Engineering, Curtin University , Perth, Western Australia 6102, Australia.

As differentiated from conventional synthetic processes, amino-functionalized hollow mesoporous silica (NH-HMS) has been synthesized using a new and facile strategy of ion-exchange-induced selective etching of amino-functionalized mesoporous silica (NH-meso-silica) by an alkaline solution. Nuclear magnetic resonance (NMR) spectroscopy and in situ time-resolved small-angle X-ray scattering (SAXS) reveal that ion-exchange-induced selective etching arises from the gradient distribution of OH in the NH-meso-silica nanospheres. Moreover, the ion-exchange-induced selective etching mechanism is verified through a successful synthesis of hollow mesoporous silica. After infiltration with phosphotungstic acid (PWA), PWA-NH-HMS nanoparticles are dispersed in the poly(ether sulfone)-polyvinylpyrrolidone (PES-PVP) matrix, forming a hybrid PWA-NH-HMS/PES-PVP nanocomposite membrane. The resultant nanocomposite membrane with an optimum loading of 10 wt % of PWA-NH-HMS showed an enhanced proton conductivity of 0.175 S cm and peak power density of 420 mW cm at 180 °C under anhydrous conditions. Excellent durability of the hybrid composite membrane fuel cell has been demonstrated at 200 °C. The results of this study demonstrated the potential of the facile synthetic strategy in the fabrication of NH-HMS with controlled mesoporous structure for application in nanocomposite membranes as a technology platform for elevated-temperature proton exchange membrane fuel cells.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acsami.7b09591DOI Listing
September 2017

Covalently cross-linked sulfone polybenzimidazole membranes with poly(vinylbenzyl chloride) for fuel cell applications.

ChemSusChem 2013 Feb 9;6(2):275-82. Epub 2013 Jan 9.

Department of Chemistry, College of Sciences, Northeastern University, Shenyang 110819, PR China.

Covalently cross-linked polymer membranes were fabricated from poly(aryl sulfone benzimidazole) (SO(2)PBI) and poly(vinylbenzyl chloride) (PVBCl) as electrolytes for high-temperature proton-exchange-membrane fuel cells. The cross-linking imparted organo insolubility and chemical stability against radical attack to the otherwise flexible SO(2)PBI membranes. Steady phosphoric acid doping of the cross-linked membranes was achieved at elevated temperatures with little swelling. The acid-doped membranes exhibited increased mechanical strength compared to both pristine SO(2)PBI and poly[2,2'-(m-phenylene)-5,5'-bibenzimidazole] (mPBI). The superior characteristics of the cross-linked SO(2)PBI membranes allowed higher acid doping levels and, therefore, higher proton conductivity. Fuel-cell tests with the cross-linked membranes demonstrated a high open circuit voltage and improved power performance and durability.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/cssc.201200716DOI Listing
February 2013

Regiospecific one-pot synthesis of diaryliodonium tetrafluoroborates from arylboronic acids and aryl iodides.

J Org Chem 2008 Jun 28;73(12):4602-7. Epub 2008 May 28.

Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, Stockholm, Sweden.

Diaryliodonium salts have recently received considerable attention as mild arylation reagents in organic synthesis. This paper describes a regiospecific, sequential one-pot synthesis of symmetrical and unsymmetrical diaryliodonium tetrafluoroborates, which are the most popular salts in metal-catalyzed arylations. The protocol is fast and high-yielding and has a large substrate scope. Furthermore, the corresponding diaryliodonium triflates can conveniently be obtained via an in situ anion exchange.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/jo8004974DOI Listing
June 2008
-->