Specifically, for FeSA-N5-C, the rate-determining step of catalytic oxidation is the process from IS1 to IM1, with an energy barrier of 0.58 eV. CO2 and H2O desorb from FeSA-N5-C with 0.36 and 0.16 eV, respectively. The reaction products are physically adsorbed on catalyst surface and adsorption energy is relatively low, so the product molecules are easily desorbed from FeSA-N5-C surface, which is beneficial for catalytic oxidation reaction cycle. Satisfyingly, FeSA-N5-C has the lowest energy barrier for catalytic oxidation of HCHO, resulting in its highest catalytic activity among these three catalysts. Therefore, based on the above reaction path analysis, FeSA-N5-C is a highly desirable candidate for the later experimental preparation.