请用专业的学术英语润色这段话To further rationalize the superior activity of Fe-O single-atom catalysts Gibbs free energy diagrams were calculated for the oxidation of AA to DHA for four different metal single-atoms

To further rationalize the superior activity of Fe-O single-atom catalysts, Gibbs free energy diagrams were computed for the oxidation of ascorbic acid (AA) to dehydroascorbic acid (DHA) for four different metal single-atoms at U = 0 V and 1 V (Fig. 4d and Fig. S13). The reaction commences with the formation of adsorbed ascorbate by deprotonation of AA on the Fe single-atom catalyst, as illustrated in Fig. 4e. Subsequently, an electrophilic adsorption process occurs between the metal cation, followed by HA- anion deprotonation and electron loss. Finally, a process of metal and DHA desorption takes place. Calculations reveal a negative Gibbs free energy for step I for all metals, signifying that this process can be spontaneous. The Gibbs free energy diagram shows that Step II is the rate-determining step (RDS) for all metal oxide catalysts. The C, O, and H electron transfer in the enol-like structures of HA- and metal-adsorbed HA- were analyzed using the Bader charge calculation method (Figs. S14-15). We found that the charge of H in the adsorbed HA- was higher than that in the initial HA-, indicating a weaker polarization of -OH and shorter -OH bond lengths. In particular, the amount of charge transfer and bond length change of the adsorbed HA- on the FeOδ single-atom catalyst was more pronounced than the other three metal oxide single-atom catalysts. It was further demonstrated that the Fe catalyst could facilitate the dissociation of the hydroxyl group on the other side of the enol structure. These results suggest that the strong adsorption of metal cations with HA- anions leads to a weaker p-π conjugation effect of C-O in the enol structure, resulting in a weaker polarization of the hydroxyl group on the other side. As a result, the -OH group in the enol structure of the adsorbed HA- is more difficult to hydrolyze than that of the initial HA-, making this step the rate-determining step of the overall reaction.