Nanoparticle catalysts were evaluated for the evolution of H2 gas from sodium borohydride (NaBH4). The production of hydrogen gas from a chemical source such as NaBH4 is interesting because it could potentially be used as an alternative means of storing energy in fuel cells. The reaction was monitored using the redox indicator, methyl viologen (MV). In the presence of H2 gas, MV2+ is reduced to the radical cation MV+*, and hence the rate of reduction of MV2+ over time indirectly reflects the rate of production of hydrogen gas. This reduction can conveniently be monitored by UV-Vis spectroscopy because the radical cation MV+* has a strong absorption peak near 600 nm that corresponds to a deep blue color, whereas the other forms of MV do not absorb light strongly in this region of the spectrum. For these experiments, metal nanoparticle catalysts of controlled size were synthesized using dendrimers as the template and stabilizer. Catalytic reactions containing MV, NaBH4, nanopure water, and metal dendrimer-encapsulated nanoparticles (DENs) of varying sizes and metals were performed to test the catalytic activity of the DENs. The reaction was also monitored at various pH values to determine what effect that had on the rate and course of the reaction. Preliminary experiments showed a faster development and persistence of blue color, representing MV+*, at basic pH of 12 or 13, suggesting that the radical cation may be more stable at basic pH. The presence of palladium nanoparticles also increased the rate of the reaction, suggesting that it could be a viable catalyst for the evolution of H2 from NaBH4 stored at basic pH.

Evaluating various dendrimer-encapsulated nanoparticles as catalysts for production of hydrogen gas from sodium borohydride using methyl viologen as a redox indicator

247th National Meeting (2014)

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