Density functional theory (DFT) simulations are conducted using the Vienna ab into simulation package (VASP) software. The core region electrons were approximated by the projector augmented-wave (PAW) method, where the kinetic energy cutoff of the plane wave base was set to 500 eV. The exchange correlation was calculated using generalized gradient approximation (GGA) functions. The effect of spin polarization was taken into account to avoid errors in the calculations due to the magnetic properties of the iron atoms. To obtain a more accurate interaction between the catalyst and gas molecules, Van der Waals (VdW) interaction was considered by adopting the DFT-D3 correction. A 4 × 4 graphitic carbon supercell was chosen as the substrate for the catalyst, while the vacuum layer height was set at 15 Å.