Selective Oxidation of Methanol to Formaldehyde on Co(10–115)

Selective oxidation of methanol (CH3OH) to formaldehyde (CH2O) is a critical process in the modern chemical industry. In this work, we studied the oxidation of CH3OH on a stepped Co(10–115) surface with different oxidation states using the temperature-programmed desorption method. On the clean Co(10–115) surface, CH3OH molecules decompose into CO and H2 totally. After O2 preadsorption, the reaction channel of CH3OH oxidation changes with increasing O2 exposure. At low O2 exposures, the formation of CO and H2 produced from methoxy (CH3O) dissociation is still the major reaction pathway. At higher O2 exposures, CH2O formation becomes dominant due to the formation of cobalt oxide. The selectivity of CH2O product reaches ∼64% at 1.82 L O2 exposure. The high selectivity of CH2O may stem from the special structure of cobalt oxide formed at the steps, thus suppressing CO and formate production. These findings offer new insights into the rational design of catalysts by tuning the structure and oxidation state of the metal surface to regulate catalytic performance in CH2O production.