*** The diffusion of H2 adsorbed in three porous carbons investigated with in situ quasi-elastic neutron scattering method ***

Authors: Rasmus Palm(1), Heisi Kurig(1), Miriam Koppel(1), Ove Oll(1), Veronika Grzimek(2), Enn Lust(1), Margarita Russina(2)

(1) Institute of Chemistry, University of Tartu, Ravila 14a, 50411 Tartu, Estonia
(2) Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, 14109 Berlin, Germany

Contact Information:
miriam.koppel@ut.ee, rasmus.palm@ut.ee

***Introductory information***

This dataset contains data collected during quasi-elastic neutron scattering experiments on the diffusion of H2 adsorbed in three
different carbide-derived carbon materials at temperatures 50-100 K and at three different H2 loading pressures. It is being made
public both to act as supplementary data for publications [1,2] and for other researchers to use this data in their own work. The
data were collected in Helmholtz-Zentrum Berlin in Germany in March 2017 (one sample - C900) and in December 2018 (two samples –
C700 and C800). The samples, denoted as C700, C800 and C900, have been synthesized from Mo2C and are named after their chlorination
temperature in degrees in Celsius.

[1] Härmas, Riinu; Palm, Rasmus; Russina, Margarita; Kurig, Heisi; Grzimek, Veronika; Härk, Eneli; Koppel, Miriam; Tallo, Indrek;
Paalo, Maarja; Oll, Ove; Embs, Jan; Lust, Enn (2019). Transport properties of H2 confined in carbide-derived carbons with different
pore shapes and sizes. Carbon, 155, 122?128. DOI: 10.1016/j.carbon.2019.08.041.
[2] Koppel, Miriam; Palm, Rasmus; Härmas, Riinu; Russina, Margarita; Matsubara, Nami; Månsson, Martin; Grzimek, Veronika; Paalo,
Maarja; Aruväli, Jaan; Romann, Tavo; Oll, Ove; Lust, Enn (2021). In Situ Observation of Pressure Modulated Reversible Structural
Changes in the Graphitic Domains of Carbide-Derived Carbons. Carbon. DOI: 10.1016/j.carbon.2020.12.025.

This research project was made possible by funding the research through SLTKT16432T “Estonian participation in designing, construction
and application of the ESS 1.09.2015- 31.08.2023”, as well as by the Estonian Research Council through Grants PUTJD957, PRG676 and
Centers of Excellence, TK141 “Advanced materials and high-technology devices for energy recuperation systems”.

***Sample preparation and measurement details***

The data were collected using the time-of-flight spectrometer NEAT'2016 at neutron source BER II in Helmholtz Zentrum Berlin, Germany.
The averaged incident neutron wavelength was 5 Å (Ei ~ 3.3 meV) which resulted in neutron detection in the momentum transfer range, Q,
from 0.3 to 2.4 Å-1 and energy resolution, ?E, of 100 ?eV. There are Bragg diffraction peaks present in the spectra, for example the
(002) Bragg diffraction peak from graphitic carbon with a maximum at 2? ~ 26º, corresponding to ~ 1.8 Å-1. Initial data reduction and
background subtraction routines (including vanadium and empty cell corrections) have been performed using Mantid software package.
Before the quasi-elastic neutron scattering measurement, all three carbons were outgassed for > 17 h at > 250 C to remove moisture and
other adsorbed species. After the outgassing process, the samples were transferred into a double-walled cylindrical aluminum sample
holder with an  outer diameter of 1.02 cm and an inner diameter of 0.555 cm. Sample handling and preparation were performed in a glovebox
filled with inert gas. The measurement protocol for all three carbons was identical. The signal from the vanadium cell and the empty
sample holder was measured for detector normalization and background subtraction. The experiments with the three samples were conducted
as follows:
1. The signal from outgassed carbons was measured at 20 K, 50 K, 60 K, 70 K, 80 K, 90 K, and 100 K.
2. The samples were cooled down to 77 K and H2 was dosed in the sample holder until the pressure reached 0.1 bar. The adsorption equilibrium
was established in approximately 1 h.
3. The sample holder was disconnected from the gas dosing apparatus and the carbons containing H2 were measured at different temperatures 
ranging from 20 K to 100 K, i.e., the same temperature series as for the outgassed samples. After each temperature change, the system was
let to reach an equilibrium during approximately 40 min before the start of the scattering measurement. C700 was also measured at 30 K and
40 K at 0.1 bar.
Steps 2.-3. were repeated for pressures 1 and 10 bar. Data at 20 - 40 K is excluded from this dataset.

***Data specific information***

The sample files are named according to their measurement conditions. For example, C700_1bar_50K_SofQW_Q0p725 contains the neutorn scattering
data of sample C700 measured at H2 loading pressure of 1 bar at 50 K at scattering vector Q value of 0.725 Å-1. The data from outgassed carbon
adsorbent has been provided separately, where ‘1bar’ in the file name has been replaced with ‘empty’. In case of C700 and C800 at 1 bar and
10 bar, the chosen energy window was wider and thus, ‘wider’ after ‘empty’ in the file name stands from signal from outgassed C700 and C800 in
a wider energy change window (C900 data was binned in one energy window). As the first step, the signal from ‘empty’ carbon adsorbent must be
substracted from signal originating from carbon sample loaded with H2.

The data in the files are organized as three columns, where first column is neutron energy change in meV, second column is signal intensity in
arbitrary units, and third column is the error values of intensity in arbitrary units.