The Reaction Paths Of CH₂O Decomposition On CuO Surfaces:A DFT Study

In this paper,density reaction theory(DFT)is used to study the reaction mechanism of formaldehyde on CuO crystal surfaces.The main content of the research is divided into two parts:(1)the reaction path of formaldehyde on CuO(111)surface;(2)The effect of oxygen vacancies on different CuO cry stal surfaces about the oxidative decomposition of formaldehyde.For the reaction path of formaldehyde on the CuO(111)crystal surface,the reaction path of formaldehyde on the clean CuO(111)crystal surface,O and OH pre-adsorbed CuO(111)crystal surfaces were compared.The intermediates of formaldehyde reaction mainly include CHO2,CH2O2,HCO,CO,etc.The adsorption sites and reaction paths of several intermediates are compared.There are two different kinds of Cu atoms and two different kinds of O atoms on the CuO(111)surface,which are Cusub,Cusuf,Osub and Osuf.The CH2O,CH2O2,CHO2 and CO prefer to occupy the Cusub sites,while the HCO prefer occupies the Osuf sites.The decomposition path of CH2O in the clean CuO(111)is CH20?HCO?CO,while in the O and OH pre-adsorbed crystal surface,the decomposition path is CH20?CH2O2?CHO2?CO2.The pre-adsorbed O and OH could facilitate the further reaction of the intermediate product and facilitate the oxidative decomposition of formaldehyde.For the effect of different crystal surface oxygen vacancies on the oxidative decomposition of formaldehyde,the crystal surface of CuO(111)and CuO(101)are selected to research,the oxygen vacancy formation energies are calculated,and the different adsorption modes of formaldehyde are compared.The decomposition path of formaldehyde on the crystal surfaces of CuO(111)and CuO(101)with oxygen vacancy is CH2o?HCO+H?CO+2H?CO+ H2,and formaldehyde breaks two C-H bonds,eventually producing H2 and CO.On the crystal surfaces of CuO(111)and CuO(101)with oxygen vacancy,the adsorption energies of formaldehyde are greatly increased,and the adsorption configurations are different from the crystal surfaces without oxygen vacancy.However,the dehydrogenation energy barriers of formaldehyde are relatively high in the crystal surfaces with oxygen vacancy,and it is difficult to decompose.