Template‐Assisted Formation of Fullerenes from Short‐Chain Hydrocarbons by Supported Platinum Nanoparticles

Abstract

Since the discovery of C 60 fullerenes, [1] research on the respective family of carbon allotropes has grown enormously, [2] mainly motivated by potential technological applications. Fullerenes are of interest in molecular electronics and for nonlinear optical devices.[3] Metal-insulator transitions of alkali-intercalated fullerenes [4] and superconductivity of alkali-doped fullerene compounds have attracted considerable scientific attention; [5] the great interest in fullerenebased materials has boosted the search for a rational design of fullerenes by new synthesis strategies. [6] Fullerenes usually are obtained by vaporization methods, [6] but can also be synthesized from polyarene precursor C 60 H 30 (1). Scott and co-workers have reported fullerene formation in the gas phase either through a series of cyclodehydrogenation steps [7] on 1 or through cyclization of a trichloroderivative, C 60 H 27 Cl 3 . [6,8] These methods, however, lead to yields below 1 %. Recently, Otero and co-workers showed that a Pt(111) single crystal surface-mediated process can achieve almost a 100 % yield, [9,10] using 1 and the precursor C 60 H 27 N 3 (2) to eventually obtain, after annealing over 750 K, fullerene and triazafullerene species. Nevertheless, the yield for the synthesis of the precursors from commercial chemicals is still only 33 % for 1 and 56 % for 2.The great improvement of the latter studies is to employ organic compounds, whose inherent geometric structure (exhibiting several interconnected C 6 and C 5 rings) and electronic structure (strong aromaticity) favor the formation of fullerenes. Inspired by this idea the following question arises: Is it possible to synthesize fullerenes from simple and abundant precursors with the help of templates, whose specific geometric and electronic structures enable a natural formation of fullerenes? This means that the formation of fullerenes is induced by specific properties of a template which acts, in addition, as a catalyst during the synthesis process. In the ideal case, the use of pertinent templates would favor the formation of specific fullerenes and, by mixing small heteroatom-containing molecules with the precursors, of heterofullerenes.Herein we show the possibility of using supported nanoparticles as templates and catalysts for the fullerene synthesis from simple precursor molecules, considering as a proof of principle, the synthesis of a simple fullerene, C 60 , from methane or ethylene by nanometer-sized platinum nanoparticles on an oxide support. By means of state-of-the-art ab initio calculations based on DFT we give arguments for the effectiveness of this set-up. For a successful fullerene synthesis sketched here, several conditions have to be fulfilled: 1) the precursor molecules have to be completely dehydrogenated at the Pt nanoparticles, releasing the hydrogen atoms as gaseous hydrogen (H 2 (g)) at working temperature, 2) C atoms or intermediate carbon compounds have to remain at the Pt nanoparticle and must not migrate to the support, and 3) the formation of...

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