New heterogeneous acid catalyst shows high activity in release of hydrogen from sodium borohydride; lowest activation energy yet reported
A team from the Indian Institute of Technology Bombay has devised a heterogeneous acid catalyst, silica sulfuric acid, that shows high activity towards releasing hydrogen from sodium borohydride (NaBH4), with a hydrolysis rate of 5.5 L min−1 g−1. Further, the activation energy of the NaBH4 hydrolysis reaction in the presence of the catalyst was calculated to be the lowest (17 kJ mol−1) among reported heterogeneous catalysts to date.
The IIT prepared their catalyst from silica gel (SiO2) and sulfuric acid (H2SO4). A paper on their work is published in the Journal of Power Sources.
When NaBH4 is suspended in an aqueous solution and then passed over a catalyst, the reaction produces hydrogen, along with a benign byproduct—sodium metaborate—that can be recycled back into sodium borohydride.
Sodium borohydride attracted a great deal of interest beginning in the late 1990s as a hydrogen storage material, with companies and researchers working on its application in a range of applications, from portable devices to transportation. For example, then-DaimlerChrysler used Millenium Cell sodium borohydride technology it its Natrium fuel cell concept car, introduced in 2001. (Millenium Cell liquidated in 2008.)
In 2007, however, an independent technical review panel convened at the behest of the Department of Energy to consider the technical status and progress of R&D on the hydrolysis of sodium borohydride for on-board vehicular hydrogen storage unanimously recommended a “no-go” to further funding on this material for vehicular applications, due to an inability to meet DOE targets. (Earlier post.)
Issues included water handling and catalytic reactivity and durability.
Joydev Manna, Binayak Roy, Pratibha Sharma (2015) “Efficient hydrogen generation from sodium borohydride hydrolysis using silica sulfuric acid catalyst,” Journal of Power Sources, Volume 275, Pages 727-733 doi: 10.1016/j.jpowsour.2014.11.040
Demirci, U. B., Akdim, O., Andrieux, J., Hannauer, J., Chamoun, R. and Miele, P. (2010), “Sodium Borohydride Hydrolysis as Hydrogen Generator: Issues, State of the Art and Applicability Upstream from a Fuel Cell,” Fuel Cells, 10: 335–350 doi: 10.1002/fuce.200800171