Portal de Periódicos da CAPES

Adsorption and Cyclotrimerization Kinetics of C 2 H 2 at a Cu(110) Surface

2012; American Chemical Society; Volume: 116; Issue: 17 Linguagem: Inglês

10.1021/jp300514f

1932-7455

H. Öberg, Y. Nestsiarenka, Akitaka Matsuda, Jörgen Gladh, Tony Hansson, Lars G. M. Pettersson, H. Öström,

Spectroscopy and Quantum Chemical Studies

The kinetics of acetylene adsorption and cyclotrimerization was studied by vibrational sum-frequency generation spectroscopy (SFG) and density functional theory (DFT) calculations. At low temperature, SFG shows two resonances corresponding to acetylene adsorbed in two different sites. Upon heating, two new vibrational resonances appear. We interpret these resonances as being due to C2H2 island formation and adsorbed C4H4, which is the intermediate in the subsequent cyclotrimerization reaction to form benzene. A kinetic model is applied, which allows determination of the relevant activation barriers. The barrier for C2H2 diffusion is determined to be 43 ± 1 kJ/mol. The activation barrier for formation of the C4H4 intermediate is found to be 84 ± 6 kJ/mol and the barrier for benzene formation 5 ± 3 kJ/mol lower. Barriers to diffusion and formation of C4H4 and C6H6 obtained from DFT calculations are in quantitative agreement with the experiments once the locally high coverage in C2H2 islands is included.