Methanation of carbon on Ni(100) surfaces at 120 K with gaseous H atoms

Upon directing a beam of thermal (2000 K) H atoms at carbon covered Ni(100) surfaces between 120 and 250 K methane was observed as the ohey only reaction product. The initiating step Hgas + Cad → CHad was identified as rate determining. Above 250 K thermal decomposition of CH3,ad prevents C methanation. Only direct Eley-Rideal type reactions are involved in the stepwise hydrogenation of C to methane.