Proton dynamics of CsH2PO4 studied by quasi-elastic neutron scattering and PFG-NMR

A review on synthesis and characterization of solid acid materials for fuel cell applications

“…The measurements indicated a jump distance of 2.7 Å between adjacent protons, while a quasi-elastic neutron scattering (QENS) measurement assumed that the proton was liberated between phosphate tetrahedral units, with an average hopping distance of 0.8 Å, as depicted in Fig. 1(c) [84].…”

“…A study by Ishikawa et al [84] obtained a proton diffusion coefficient for CDP via PFG-NMR and 1 H NMR spin-lattice relaxation time (T 1 ) measurements at high temperatures from 238 C to 284 C. The spectrometer used in the measurements was equipped with a high temperature probe operating at 7 T and with a field gradient strength of 800 G cm À1 . The sample was pressed into a 4 mm diameter pellet and vacuum-encapsulated in a 5 mm diameter Pyrex tube.…”

Diffusion in Solid Proton Conductors: Theoretical Aspects and Nuclear Magnetic Resonance Analysis

“…The authors suggested that for the proton conduction in the paraelectric phase of CDP, the reorientation of the H 2 PO 4 À anions plays an important role. In the work by Ishikawa and coauthors, the ionic conduction behavior of the superprotonic phase of CsH 2 PO 4 was studied by 1 H pulsed field gradient NMR and 1 H NMR spin-lattice relaxation time measurements together with quasi-elastic neutron scattering (QENS; see Chapter 4 by Hempelmann) [84]. Two motional processes were recognized: the slower proton diffusion coefficient obtained from 1 H PFG-NMR was in line with the rate and activation energy of the proton transport measured by impedance spectroscopy.…”

A new apparatus design for high temperature (up to 950 °C) quasi-elastic neutron scattering in a controlled gaseous environment

“…[12][13][14] A less commonly used but powerful technique is QuasiElastic Neutron Scattering (QENS), which probes single particle dynamics with a particularly high sensitivity to the motion of protons. 9,[15][16][17][18][19][20][21][22][23][24] The sample cell and associated equipment were operated at the neutron beam at BASIS at the Spallation Neutron Source (SNS) in Oak Ridge National Laboratory (ORNL). BASIS can probe dynamic motions in different systems on the pico-to nanosecond time scale and on the length scales from ∼3 to 31 Å. QENS signal at BASIS can be measured at a wide momentum-transfer range of 0.2 Å −1 < Q < 2 Å −1 and energy transfers (ω) of up to ±200 µeV with 3.5 µeV resolution.…”

“…In previously reported QENS studies, the samples were charged with protons prior to the QENS experiment and to maintain the sample hydration during the QENS experiment; the sample was tightly sealed inside a can. Most of the time, the can was aluminum [15][16][17][18] and sometimes the aluminum can was coated with platinum to prevent corrosion. 18 The current article proposes a new sample environment built and used in SNS at ORNL to study the dynamics of diffusion in proton conductors that operate at high temperatures.…”