Reactivity of Cobalt‐Fullerene Complexes towards Deuterium

Abstract

The adsorption of molecular deuterium (D 2 ) onto charged cobalt-fullerene-complexes Co n C 60 + (n = 1-8) is measured experimentally in a few-collision reaction cell. The reactivity is strongly size-dependent, hinting at clustering of the transition metal atoms on the fullerenes. Formation and desorption rate constants are obtained from the pressure-dependent deuterogenation curves. DFT calculations indeed find that this transition metal clustering is energetically more favorable than decorating the fullerene. For n = 1, D 2 is predicted to bind molecularly and for n = 2 dissociative and molecular configurations are quasi-isoenergetic. For n = 3-8, dissociation of D 2 is thermodynamically preferred. However, reaching the ground state configuration with dissociated deuterium on the timescale of the experiment may be hindered by dissociation barriers.[a] Dr.

C60Con complexes as hydrogen adsorbing materials

“…These observations are consistent with earlier work showing the clustering of Ti atoms on the surface of the C60 fullerene [28]. The lowest energy structures of neutral C60Con, n=1-8, are the same as those previously reported for cationic C60Con + complexes [34].…”

“…Figure 6 also reports the structures corresponding to dissociative hydrogen adsorption. The hydrogen atoms occupy bridge positions between neighbor cobalt atoms, just as it occurs in the case of the cationic complexes [34]. An interesting observation is the lack of a dissociative adsorption state either on C60Co and C60Co + .…”

“…The first ionization energy of the complexes is displayed in Table 2. The tendency is a decrease of the first ionization energy with n. complexes [34], with one exception: in C60Co5 + the hydrogen molecule is adsorbed on top of a Co atom not in contact with the fullerene, but the molecule is tumbled in such a way that one H atom interacts with one Co atom in contact with the fullerene [34]. Figure 6 also reports the structures corresponding to dissociative hydrogen adsorption.…”

“…A recent explored route to increase the amount of stored hydrogen consists in doping the materials with metal atoms or nanoparticles, and promising results have been obtained for porous carbons [25,26]. Some theoretical studies of hydrogen adsorption on carbon fullerenes doped with transition and non-transition metal atoms and clusters have been performed [27][28][29][30][31][32], and recently the reactivity of alkali metal-and transition metal-fullerene complexes towards hydrogen has been studied by a combination of experimental and theoretical work [33,34]. The experimental work was based on mass spectrometry, and this means that the hydrogenated metal-fullerene complexes are actually charged, cationic complexes.…”

Doping Platinum with Germanium: An Effective Way to Mitigate the CO Poisoning

“…In the Supporting information, we estimate CO binding energies using the measured dissociation rates, employing RRKM theory that directly uses the calculated vibrational modes of the complexes to account for possible changes in heat capacity upon doping. A similar analysis has been performed for related systems [27,57,58] . The analysis confirms that the increased k d induced by doping correlates with a reduced CO binding energy and thus a weakening of the Pt‐CO interaction induced by germanium.…”