Cobalt Organic Framework Supported over Carbon-Based Materials as Novel Catalysts in the Hydrolysis of Sodium Borohydride

Abstract

It is no secret that the global supplies of fossil fuel resources have been steadily dwindling. While there is no consensus on when the reserves will be completely depleted, there has been an effort among scientists to find a new, sustainable energy source for the future. It is generally agreed that such a source needs to not only be abundant, but also avoid the harmful biproducts of current fuel sources. Some proposed energy sources include solar, wind, geothermal and more. While each of these sources have their benefits, they also have their drawbacks and the cost to install and maintain these sources, as well as the environmental damage done during their construction can offset their benefits. One potential new energy source can be found in hydrogen gas. Hydrogen is not only the most abundant element in the universe, but its gaseous form can be burned to produce only energy and water [1-12]. The biggest hurdle a hydrogen economy faces is in the storage of the highly combustible gas. An interesting method of storing hydrogen is via adsorption within the chemical structure of a molecule. Sodium borohydride (NaBH4) for example is a chemical that contains 10.8% hydrogen by weight and steadily releases hydrogen gas when mixed with water.1 In order to efficiently utilize this reaction a catalyst is required. Typical catalysts are often precious metals like platinum, gold, and palladium, which tend to be expensive to use. By forming these metals into nanoparticles, their surface area can be increased, which increases their catalytic potential, however, these nanoparticles have a tendency to agglomerate in solution. Previous work by this team explored the catalytic capability of these metals and notes the use of carbon-based support structures can mitigate this agglomeration.2-4 This study aims to expand on those studies by using cobalt nanoparticles, which is a more cost-effective metal. Two novel Cobalt terephthalate complexes were combined with graphene and multiwalled carbon nanotubes (MWCNT) respectively, then tested for their ability to catalyze the hydrolysis of sodium borohydride. These materials were characterized using Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Powdered X-ray diffraction (P-XRD), and Fourier Transform Infrared spectroscopy (FTIR). It was observed that after a single reaction, our materials appeared to be converted into cobalt borohydrides. The hydrogen produced for each material was 73 mL and 76 mL for the graphene and MWCNT materials, respectively. This study provides a possible method for producing cheaper, cleaner energy for a more sustainable future.