LEED and Mass Spectrometry Studies of Benzene and Cyclohexane Adsorption on Nickel Single Crystal Faces

Benzene adsorption at 25 °C on nickel single crystal (111) and (110) faces gives oriented LEED patterns. Mass spectrometry analysis of gases desorbed by heating shows that a part of benzene is adsorbed reversibly, whereas another part is completely cracked as hydrogen, and carbon is left on the surface. Self-hydrogenation can be observed and followed on the (110) face. Cyclohexane adsorption at 25 °C gives a (1×2) LEED pattern at low coverage on (110) face. No oriented structure is observed on the (111) face. In contrast to benzene adsorption we only observe hydrogen in the gas phase by thermal desorption. Benzene and cyclohexane adsorption at higher temperatures give LEED patterns that we assume to be due to carbide formation on the surface. These results are discussed and compared with those of ethylene and ethane adsorption.