Reactions of diazomethane on a clean, H-covered and O-covered Pt(111) surface

The reactions of diazomethane on a clean, a H-covered, and an O-covered Pt(111) surface were studied by temperature programmed desorption. Methane, ethylene, and hydrogen were the desorption products for the clean surface. The same products were observed together with nitrogen for the H-covered surface. Comparison of the desorption profiles on the clean and H-covered surfaces with those for ethylene and acetylene showed that methane was formed from the hydrogenation of surface methylene species that were formed by the dissociation of diazomethane on adsorption. Some of the surface methylene species also combined to form ethylene before undergoing further reaction. On the O-covered surface, products characteristic of the clean surface were observed together with the oxidation products water, CO and CO₂. Some of the water was formed by the reaction of hydrogen released in the decomposition of methylene. The remaining water, CO, and CO₂ were formed by the oxidation of an intermediate of stoichiometry CH, similar to the oxidation of ethylene and acetylene.