(Invited) Efficient Production of Hydrogen Using Composite Nanomaterial Electrode: A Step towards Using Solar Powered Electrolyzer

The need for using fuels that produce lesser pollution has been realized in this decade (1,2). The literature projects hydrogen gas as one of the possible fuels in this category (2)   as the fuel value of hydrogen is nearly three times that of gasoline (H₂=142 kJ/g;  gasoline=48 kJ/g) (1) and its combustion produces water. The attractive fuel value of hydrogen has motivated a large number of scientists and engineers to evolve new technologies using hydrogen. Due to the limited abundance of  hydrogen in the free form, it is necessary to explore methods of generating hydrogen from the combined form in which it exists in this world; the most abundant element in this universe is hydrogen, 75%  of it exists as water. In order to produce hydrogen from water it is necessary to use a chemical or an electrochemical method.  In the latter method, several electrolyzers have been  reported  in the literature (3-6). Advances in nano materials have been fascinating with the discovery of carbon nanotubes and graphene. A ferro magnetic atom such as Ni has been shown to undergo spin polarization when it is  interacting with carbon nanotubes (7,8).  Ni atom having electronic configuration [Ar}3d¹⁰4s² when spin polarized modifies its electron configuration. This interaction is  studied by thermogravimetric analysis (TGA). The ratio of spin polarizer to Ni atom of 5 is required for achieving highest degree of polarization.  The effect of spin polarization is to protect it from air oxidation that  is conducive for utilization of it as an electrode. An electrode has been fabricated with atomized Ni and multiwalled carbon nanotubes (Ni-MWCNT) (area=0.0946 cm²) that is coupled with graphite  electrode in an electrolyzer. The electrolysis of water is carried out using several different electrolytes such as sodium sulfate, sodium hydroxide and sulfuric acid. Hydrogen gas that is produced at different current densities is  measured to determine  the coulombic  and power efficiencies. Since noble metal like platinum is known to be an ideal cathode for the reduction of hydrogen, experiments are also carried out using a platinum cathode for a relative comparison. Cyclic voltammetric curves are recorded using the atomized Ni-MWCNT in different electrolytes for examining the electrocatalysis (9).

 

1. R. Press, K.S.V. Santhanam, M.Miri, A. Bailey and G.Takacs, Introduction to Hydrogen Technology, Wiley, NJ (2009)
2. A. Zuttel, A.  Remhof, A. Borgschulte and O.  Friedrichs,  Philosophical Transactions of the Royal Society, A: Mathematical, Physical & Engineering Sciences  (2010),  368(1923),  3329-3342. 
3. D. Marcelo and A. Dell’Era, Int. J. Hydrogen Energy, 3041 (2008)
4. J. S. Herring, J.  O’Brien, C.M.  Stoots, G.l. Hawkes, J.J. Hartvigsen and  M. Shahnam, Int. J. Hydrogen, 32, 440 (2007)
5. L. D. Munoz, A. Bergel, D. Feron and R. Basseguy, Int. J. Hydrogen Energy, 35, 8561 (2010)
6. M. A. Rosen and D. S. Scott, Int. J. Hydrogen Energy, Vol. 23, No. 8, pp. 653459, 1998
7. S.B. Fagan, R. Mota, A.J.R. da Silva and A. Fazio, Phys. Rev. B, 67, 205414 (2003)
8. a) K.S.V. Santhanam, X. Chen and S. Gupta, J. Nanoscience and Nanotechnology, 14, 2842 (2014)

          b) M. Kumar, N. Rawat and K.S.V. Santhanam, Mat. Res. Soc. Symposium, Materials Research Society,

           Warandale, Pa (2006), Vol.899E, pp. 899-N07-01.1

     9.  A.J. Bard and L.R. Faulkner, Electrochemical Methods, Wiley, NJ, (2000)