Regular Article

Experimental and theoretical investigation of Fe-catalysis phenomenon in hydrogen thermal desorption from hydrocarbon plasma-discharge films from T-10 tokama^★

¹ National Research Centre Kurchatov Institute, 123182 Moscow, Russia
² Moscow Institute of Physics and Technology, 141700 Dolgoprudny, Russia

^* e-mail: vl-stan@mail.ru

Received: 27 June 2017
Received in final form: 18 September 2017
Accepted: 27 September 2017
Published online: 27 October 2017

Abstract

Investigations of the effect of Fe impurities on D₂ thermal desorption (TD) from homogeneous CD_x films (x ∼ 0.5) formed in the D-plasma discharge of the T-10 tokamak were carried out. The experimental TD spectra of the films showed two groups of peaks at 650–850 K and 900–1000 K for two adsorption states. The main result of the iron catalysis effect consists in the shift of the high-temperature peak by −24 K and in the increase in the fraction of the weakly bonded adsorption states. To describe the effect of iron impurities on TD of hydrogen isotopes, a structural cluster model based on the interaction of the Fe⁺ ion with the 1,3-C₆H₈ molecule was proposed. The potential energy surfaces of chemical reactions with the H₂ elimination were calculated using ab initio methods of quantum chemistry. It was established that the activation barrier of hydrogen TD is reduced by about 1 eV due to the interaction of the Fe⁺ ion with the π-subsystem of the 1,3-C₆H₈ molecule leading to a redistribution of the double bonds along the carbon system.