Supplementary 1
Temperature-Programmed-Desorption of Li-N-H
samples
8.0x10
-6
(a) H2
6.0x10
Intensity (a.u.)
4.0x10
2.0x10
Hydrogenated Li2NH
Hydrogenated Li3N
-6
-6
-6
0.0
100
1.5x10
1.0x10
5.0x10
200
300
400
500
200
300
400
500
-8
(b) NH3
-8
-9
0.0
100
Temperature (oC)
H2 and NH3 signals detected by Mass-Spectrometer in the desorption of hydrogenated
Li3N and Li2NH samples. Temperature was raised at 2°C/min from 100°C to 400°C for
hydrogenated Li2NH sample and from 100°C to 500°C for hydrogenated Li3N sample.
1
Supplementary 2
Interaction of LiNH2 and LiH
1.4E-5
245
H2
iii
1.0E-5
269
ii
6E-6
391 441
Intensity
2E-6
7E-7
i
374
NH3
5E-7
i
3E-7
421
1E-7
ii
iii
3.0E-8
373
2.0E-8
441
N2
i
428
ii
1.0E-8
iii
0
100
i. Pure LiNH2;
200 300 400 500
Temperature ( oC)
ii. LiNH2+LiH (1/1);
600
iii. LiNH2+2LiH (1/2)
This figure presents Temperature-programmed-desorption/decomposition results of the
above three samples. For pure LiNH2, it decomposes mainly to NH3 at temperature
higher than 300C, small amount of N2 and H2 come out at temperature higher than
350C; when LiNH2 mixes with LiH, H2 comes out at temperatures around 150C, which
is ~ 150C lower than the setout point of LiNH2 decomposition revealing there exists
certain interaction of LiNH2 and LiH. Temperature was raised from 100°C to 500°C at
1°C/min interval. ~ 230 mg sample was tested each time.
2
Supplementary 3
Hydrogen interaction with Ca2NH
527
Intensity (a.u.)
462
TPR
200
300
TPD
400
500
600
Temperature ( oC)
700
This Figure illustrates the temperature-dependence of H2 absorption (TPR) and
desorption (TPD) in Ca2NH sample. It reveals that hydrogen can be absorbed by Ca2NH
at temperature above 300C and can be desorbed from hydrogenated Ca2NH at
temperature above 400C. Noted that the decomposition of CaH2 requires temperature
above 650C. ~ 500 mg sample was tested.
Intensity (a.u.)
Ca2NH
CaNH
X CaH2
CaO
H2+ Ca2NH
Pristine Ca2NH
1
0
2
0
3
4
5
0 2 Theta
0
0
6
0
7
0
This Figure shows the structure and composition of Ca2NH before and after hydrogen
absorption. It demonstrates that after absorption, CaNH and CaH2 were developed.
3
Supplementary 4
Van’t Hoff Plot
0.4
0.0
Ln(P)
-0.4
Ca2NH
Li2NH
-0.8
-1.2
-1.6
-2.0
-3
-3
-3
1.2x10 1.6x10 2.0x10 2.4x10
-3
-1
1/T (K )
Van’t Hoff plots of Li2NH and Ca2NH systems. The slope of each line can be used to
calculate the enthalpy of H absorption in these two systems according to the equation:
InPH2 = H/RT - S/T
4
Supplementary 5
Kinetics of Absorption
4.0
Li3N-255oC
3.5
H / M-N-H
3.0
2.5
Li2NH-255oC
2.0
1.5
Ca2NH-500oC
1.0
0.5
0.0
0
10
20
30
Time (min)
Kinetics of absorption was measured by Autosoak mode embodied in PCI unit. ~ 500 mg
sample was heated to desired temperatures, and then, sample chamber was flushed with
30 bars of hydrogen. Hydrogen absorption was measured with time.
5
Supplementary 6
Recyclability of Li3N, Li2NH and Ca2NH systems
7
Li2NH
6
wt% H2
5
Li3N
4
3
2
Ca2NH
1
0
0
2
4
6
8
10
No. of cycles
This figure shows hydrogen storage capabilities of Li3N, Li2NH and Ca2NH samples with
cycles of absorption and desorption.
6