Various states of water species in an anion exchange membrane characterized by Raman spectroscopy under controlled temperature and humidity

Abstract

Anion exchange membrane fuel cells (AEMFCs) hold the key to future mass commercialisation of fuel cell technology, even though currently, AEMFCs perform less optimally than proton exchange membrane fuel cells...

Measurement of Water Uptake and States in Nafion Membranes Using Humidity-Controlled Terahertz Time-Domain Spectroscopy

“…Dielectric spectroscopy could be an alternative to probe strongly bound water with microsecond relaxation time at ambient temperatures . Elucidating the different water states across different techniques is therefore subject to future investigation including the recently proposed environmentally controlled Raman spectroscopy. , …”

“…10 Elucidating the different water states across different techniques is therefore subject to future investigation including the recently proposed environmentally controlled Raman spectroscopy. 99,100 3.3. Practical Limitations.…”

Transient Distribution of Water in an Anion Exchange Membrane Fuel Cell Monitored by Operando Coherent Anti-Stokes Raman Scattering Spectroscopy

“…During assembly, a pinhole of 0.5 mm was punched at the center of the anode for optical access to the membrane. 44,46,[48][49][50][51]70 A Pt foil of the same diameter size as the pinhole was then placed between the QPAF-4 film and the GDE on the cathode side for the efficient reflection of the CARS light. A transparent quartz window 16 mm © 19 mm in area and 200 µm in thickness was mounted at the anode end plate to irradiate laser lights and detect the CARS signal.…”

“…Our recent papers 70,71 discussed the OH speciation in AEMs using both Raman and CARS spectroscopy. In this paper, reference will be made to the discussed species, which are based on donoracceptor relationships in liquid water.…”

“…[72][73][74][75] Briefly, the species expected in the QPAF-4 membrane during power generation are: (1) OH H-bonded directly to OH ¹ around 2880 cm ¹1 , (2) C-H in the ammonium group around 2942 cm ¹1 , (3) C-H on the benzene ring around 3091 cm ¹1 , (4) single donor double acceptor H-bonded water (DAA) around 3163 cm ¹1 , (5) double donor double acceptor (DDAA) H-bonded water around 3187 cm ¹1 , (6) single donor single acceptor (DA) water around 3348 cm ¹1 , (7) double donor single acceptor (DDA) H-bonded water around 3470 cm ¹1 (8) non-H-bonded water around 3510 cm ¹1 and (9) OH ¹ around 3725 cm ¹1 . 70 It must, however, be added that the OH peaks are expected to undergo some displacements in confined spaces such as polymer membranes. 76 Also, since OH ¹ is known to have a strong effect on H-bonding networks, 77 further shifts in peaks are expected as the ratio of OH ¹ to water changes.…”