Structure Sensitivity of CO Oxidation on Co 3 O 4 : A DFT Study

The reaction mechanism of CO oxidation on the Co 3 O 4 (110) and Co 3 O 4 (111) surfaces is investigated by means of spin‐polarized density functional theory (DFT) within the GGA+U framework. Adsorption situation and complete reaction cycles for CO oxidation are clarified. The results indicate that 1) the U value can affect the calculated energetic result significantly, not only the absolute adsorption energy but also the trend in adsorption energy; 2) CO can directly react with surface lattice oxygen atoms (O 2f /O 3f ) to form CO 2 via the Mars–van Krevelen reaction mechanism on both (110)‐B and (111)‐B; 3) pre‐adsorbed molecular O 2 can enhance CO oxidation through the channel in which it directly reacts with molecular CO to form CO 2 [O 2 (a)+CO(g)→CO 2 (g)+O(a)] on (110)‐A/(111)‐A; 4) CO oxidation is a structure‐sensitive reaction, and the activation energy of CO oxidation follows the order of Co 3 O 4 (111)‐A(0.78 eV)>Co 3 O 4 (111)‐B (0.68 eV)>Co 3 O 4 (110)‐A (0.51 eV)>Co 3 O 4 (110)‐B (0.41 eV), that is, the (110) surface shows higher reactivity for CO oxidation than the (111) surface; 5) in addition to the O 2f , it was also found that Co 3+ is more active than Co 2+ , so both O 2f and Co 3+ control the catalytic activity of CO oxidation on Co 3 O 4 , as opposed to a previous DFT study which concluded that either Co 3+ or O 2f is the active site.