**6. Conclusions**

Ammonia is among the most commonly shipped bulk-produced chemicals, marketed for more than a decade in mass all over the globe. Originally used in the chemical industries and as an intermediate for the production of fertilisers, ammonia has also been explored recently as a hydrogen storage media and a substitute fuel for hydrocarbon. Unlike the conventional ammonia production process that used natural gas as a feedstock and is responsible for carbon emission, ammonia is a means of renewable energy storage formulated from H2 generated by an electrically driven electrolyser and N2 separate from the atmospheric air. In addition to that, innovative approaches, such as photocatalysis, electrocatalysis and plasmacatalysis, have attracted widespread interest in ammonia synthesis today. Thus, the application of ammonia as a renewable energy carrier not only plays a key role to lower GHG emissions but also allows transporting H2 efficiently and economically, permits the direct conversion to electricity by fuel cell and provides versatility in its use, as fuel for the IC engine and power generation. Thus, the ease of processing, transporting and using NH3 makes it an appealing choice to serve as the link between renewable energy production and demands. However, work is still needed to improve the efficiency of the conversion process for the chemical to compete with hydrocarbon fuel.

**Author Contributions:** Original draft preparation, M.H.H.; Supervision, T.M.I.M. and M.M.; Review and Editing, H.C.O. and I.M.R.F. Revision, A.S.S.; and F.H. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Acknowledgments:** This study was carried out under the International Research Scholarship (IRS) and UTS Presidential Scholarship (UTSP) program, funded by the University of Technology Sydney, Australia.

**Conflicts of Interest:** The authors declare no conflict of interest.
