Macroscopic Study on the Behavior of Spillover Hydrogen Atoms

We report on a macroscopic study on the behavior of spilloverHatoms using carbon black-supported Pt nanoparticles (CB/Pt) and variousorganic compounds adsorbed by microporous activated carbon (AC). Theorganic compound-adsorbed ACs are mixed with CB/Pt, and the mixturesare exposed to H-2 at 25 & DEG;C. Therein, H-2 molecules dissociatively adsorb onto the Pt nanoparticles, and Hatoms spill over from the Pt nanoparticles to the CB particles. Subsequently,the H atoms undergo secondary spillover from the CB to the AC particlesand diffuse inside the organic compound-filled micropores of the AC.From the results obtained, at least 1430 H atoms spill over from onePt nanoparticle per second (5.15 million H atoms in 1 h). The spilloverH atoms readily react with the unconjugated C C groups insidethe AC pores. The H atoms also react with C O groups; however,the reactivities of the C C and C O groups are significantlydecreased by extending the & pi;-conjugation system. Meanwhile,H atoms do not react with many other oxygen-containing functionalgroups or polycyclic aromatic hydrocarbons. These results suggestthat hydrogen storage capacities using hydrogen spillover may be overestimatedby the irreversible reactions of spillover H atoms with the aforementionedfunctional groups when using chemically treated carbon-based materials(e.g., graphene oxide), owing to the existence of many functionalgroups.