Electrochemical oxidation of methane at metal and metal oxide electrodes. Final report, December 1, 1986-December 1, 1989

An objective of the research was to gain insight into the role of surface geometry, heat of reaction, force constants and adsorption site in the activated chemisorption of methane to adsorbed hydrogen and adsorbed methyl. The model successfully calculated the activation energy for abstraction of H from CH4 by O atoms in the gas phase. The results for two crystal planes of Ni were in very good agreement with experimental findings and other calculations. For Ni(111) and Ni(110) Ea = 14 and 18 kcal/mol, respectively. The minimum electrode potential for adsorption of methane, OH, and O atoms on various metal electrodes was calculated. The open circuit decay method was employed to measure the rate of reaction between hydrocarbons including methane and adsorbed oxygen species on Pt, Pd and Rh electrodes. The rates of reaction with Pt-OH at 95C in 0.5 M H2SO4 followed the trend CH4 < C2H6 < C3H8 < H2. The faradaic efficiency for CO2 was 80% at 0.25 V vs SCE, indicating that deep oxidation occurs as desired in fuel cell applications.