ben's poster

Chun Hong Ben, Ng and Dr Luis Hererra

School of Chemical Engineering, The University of Adelaide.

*a1189835@student.adelaide.edu.au

Hydrogen storage enhancement on Li and K doped carbon

nanotubes

Introduction

Hydrogen is seen as the fuel for the future due to clean

combustion, renewability and high energy content

properties. However, the main issue concerning hydrogen

fuel is the limited storage capacity at room temperature

and pressure. In this work, unmodified and alkali modified

carbon nanotubes were simulated in order to identify a

suitable carbon structure that can meet the U.S.

Department of Energy (DOE) target of 6.5 wt% or 62 kg/m3

Hydrogen storage for automobile applications [1]. Grand

Canonical Monte Carlo simulation was used to simulate

the hydrogen adsorption isotherms of the carbon

structures under various pressures and ambient

temperature.

Aim To compare and identify the most suitable alkali modified

carbon nanostructure for enhanced hydrogen storage. This

is achieved by:

1) Determining Li and K dopant positioning on carbon

structures

2) Comparing single walled carbon nanotubes and

bundles for H2 storage

Based on the results, alkali doped carbon nanotubes have

higher hydrogen storage capacity as compared to

unmodified carbon structures. Carbon nanotube bundles

have higher interstitial forces between the carbon

nanotubes which resulted in larger storage than carbon

SWNT. Li doped carbon structures have slightly higher

hydrogen adsorption capacity than K doped carbon

structures. Both doped carbon structures met the DOE

target only at 10MPa conditions.

Future Work

To compare different dopant positioning of Li-doped

carbon nanotubes under cryogenic conditions.

References: [1] Yuan, X., et al., Monte Carlo simulation of hydrogen

physisorption in K-doped single walled carbon nanotube array.

Applied Surface Science, 2009. 255(18): p. 8122-8125.

Conclusion

Results

The hydrogen adsorption isotherms of unmodified and

alkali modified carbon nanotubes were generated from

Grand Canonical Monte Carlo simulation.

0

2

4

6

8

10

12

14

16

0 2 4 6 8 10 12

Hyd

rog

en

ad

so

rpti

on

(m

mo

l/cc)

Pressure (MPa)

Carbon SWNT at 298K

K-Doped

Li-Doped

Undoped

0

5

10

15

20

25

30

35

40

0 2 4 6 8 10 12

Hyd

rog

en

ad

so

rpti

on

(m

mo

l/cc)

Pressure (MPa)

Carbon Nanotube Bundles at 298K

K-doped

Li-Doped

Undoped

Methodology

Structure Generation and Simulation Box Setup

Helium Gas Expansion Calculations

Isotherms Generation

Storage Capacity Calculation

Figure 1: Li-doped SWNT and bundle dopant positioning

Table 1: Lennard Jones parameters

Atom ε /k (K) σ (nm) Charges

C 28.20 0.3400 -

H 36.70 0.2958 At Figure 2

He 10.22 0.2556 -

K 421.0 0.4115 +0.83

Li 567.0 0.2728 +0.45

Figure 3: Snapshots of unmodified and Li-doped SWNT at 1MPa

+2.051 +2.051 -4.096

Figure 2: Dipole charges of H2 model