Fig. 4. Energy diagram of cycle I, schematic representation is shown in Fig. 2. (A) CH₄ → CH₃OH, (B) CH₃OH → CH₂O in two steps (yellow) and in one step (purple), (C) H₂CO → HCOOH (dark blue), and its consecutive oxidation to CO₂ (orange), (D) CH₂O → CO (light blue) and its consecutive oxidation to CO₂ (brown). The reference point for all reactions is the active site and the adsorbed molecule as represented in Fig. 2.