Converting Ammonia to Hydrogen Gas using Defective Graphene

In the last decade, graphene has been researched extensively because of its unique

chemical, electronic and physical properties that can be exploited for numerous

applications. Graphene has shown promise in energy storage, gas sensors, nano-

devices and catalysts. [1] Recent studies have shown that the presence of naturally

occurring defects can activate graphene for chemical functionalization. [2] For instance,

the presence of a simple single point vacancy defect has been shown to significantly

increase chemical reactivity towards H2, NOx, SO2 and NH3. [3,4] Primarily, research has

been carried out with the purpose of functionalizing this active site, typically through

heteroatom doping of some form. [5]

We have investigated the possibility of using the innate reactivity of the single vacancy

to promote the dissociation of ammonia (NH3) and achieve graphitic nitrogen doping

and hydrogen gas (H2) formation. Nitrogen doped graphene is a highly sought-after

material, with applications in supercapacitors and bio-sensing technology. Meanwhile,

efficient production and storage of H2 gas is highly desirable for a source of renewable

energy.

The dissociation pathway for ammonia with single vacancy graphene was studied

through a series of calculations using CASTEP, an efficient and scalable plane waves

DFT code. All calculations were spin polarised and paired with vdW corrections of the

Tkatchenko-Scheffler (TS) type. We have found a potential dissociation pathway which

ammonia could undergo at moderate temperatures, in which hydrogen movement was

dominated by hydrogen diffusion steps from the defect site.

References

1 L. Rodríguez-Pérez, M. Á. Herranz and N. Martín, Chem. Commun., 2013, 49, 3721–3735.

2 S. T. Skowron, I. V. Lebedeva, A. M. Popov and E. Bichoutskaia, , DOI:10.1039/c4cs00499j.

3 S. Dandeliya and S. Anurag, IEEE Sens. J., 2019, 19, 2031–2038.

4 X.-J. Wu, Z.-J. Fei, W.-G. Liu, J. Tan, G.-H. Wang, D.-Q. Xia, K. Deng, X.-K. Chen, D.-T. Xiao, S.-W. Wu and W. Liu, Nucl. Sci. Tech., 2019, 30, 69.

5 B. Wang, L. Tsetseris and S. T. Pantelides, J. Mater. Chem. A, 2013, 1, 14927.