1. Fuel Cell Institute, Universiti Kebangsaan Malaysia, Bangi, Selangor DE 43600, Malaysia;
2. Faculty of Mathematics and Sciences, Department of Chemistry, Sriwijaya University, Inderalaya 30662, Indonesia e-mail:
3. Fuel Cell Institute, Universiti Kebangsaan Malaysia, Bangi, Selangor DE 43600, Malaysia e-mail:
4. Faculty of Engineering and Built Environment, Department of Chemical and Process Engineering, Universiti Kebangsaan Malaysia, Bangi, Selangor DE 43600, Malaysia
5. Fuel Cell Institute, Universiti Kebangsaan Malaysia, Bangi, Selangor DE 43600, Malaysia