Hydrogen Uptake of Platinum-Doped Graphite Nanofibers and Stochastic Analysis of Hydrogen Spillover

Abstract

Graphite nanofibers (GNFs) were doped with platinum in an attempt to activate the materials for moderate temperature hydrogen adsorption. Characterization of the 1% Pt/GNF sample indicates well-dispersed, metallic platinum particles ranging from 2 to 5 nm in diameter. At 27 °C and 20 bar, the hydrogen uptake of 1% Pt/GNF was less than 0.1 wt % and showed no increase relative to the GNF precursor within experimental detection limits. To explore this apparent anomaly, a stochastic Monte Carlo simulation was used to analyze the hydrogen spillover process for idealized two-dimensional surfaces with two surface types with interfacial mass transfer from the first to the second surface site. The model suggests interfacial mass transfer may not improve overall surface coverage when the rates of adsorption and desorption to the support are comparable. Dimensionless groupings are introduced to the stochastic simulation to explore the conditions in which interfacial transfer will lead to significant surface coverage...