An ab initio investigation on the mechanism of formaldehyde oxidation: A case of heterogeneous catalytic reaction over graphene-like MnO2 monolayer anchored different single atoms (Fe, Co, and Ni)

To meet the requirement of high catalytic activity and low cost, monatomic catalysis has gradually become a research hotspot. Thus, it is proposed a graphene-like MnO2 anchored different single atoms (Co, Fe, and Ni) as a catalyst to decompose gaseous HCHO into CO2 and H2O. Meanwhile, it is thoroughly investigated reaction mechanism through the density functional theory. Both the Langmuir-Hinshelwood (L-H) mechanism and the EleyeRideal (E-R) mechanism are discussed through five reaction paths, which is explored the energy barrier for each step and the heat of reaction in detail. The possible reaction pathway for catalytic HCHO oxidation over M−MnO2 is HCHO + O2 → HCOOOH → HCOH + OH → CO2 + H2O. The energy barrier of the rate-determining step in Fe-MnO2 is lower than those of Co-MnO2 and Ni-MnO2. At the same time, all the reactions in the five routes can proceed spontaneously in the temperature range of 300–800 K, which is proved by thermodynamic and kinetic analysis. The higher temperature has a positive meaning for reaction. The Arrhenius activation energy of Fe-MnO2 is lower than the other two catalysts, indicating that the Fe-MnO2 catalyst presents better catalytic performance than Co-MnO2 and Ni-MnO2.