A model of hydrogen spillover that provides a mechanistic understanding of the resulting surface concentration attributed to hydrogen spillover is proposed. Four models are developed to describe this process, including a chemical kinetics model, a kinetic Monte Carlo analysis, a dimensional analysis of the process, and use of a Langmuirian model to provide a simplified chemical kinetics analysis. The fourth model is presented in detail and its resulting spillover isotherm, which has allowed comparison of recent experimental results in hydrogen storage of doped carbon nanomaterials at ≤ 20 bar. Langmuir discussed a fifth case of adsorption, which involved dissociation of the adsorbate and ultimately led to this common assertion. However, Langmuir clearly states that this equation is valid only in the limiting case where surface coverage approaches zero. The spillover isotherm fits experimental data for a 1% Pt/SWNT very well at ≤ 20 bar. The spillover isotherm exhibits properties similar to that of the classic Langmuir isotherm. This limiting capacity provides a more realistic view of potentially applying carbon-metal hybrids to hydrogen-storage applications, than the common statement that uptake is proportional to the square root of pressure. This is an abstract of a paper presented at the ACS Fuel Chemistry Meeting (San Diego, CA Spring 2005).
|Original language||English (US)|
|Number of pages||2|
|Journal||Am Chem Soc Div Fuel Chem Prepr|
|Publication status||Published - 2005|
All Science Journal Classification (ASJC) codes