Meanwhile, the strong correlation also exists between η ORR and ∆𝐺 𝑂𝐻 * , demonstrating that the desorption of *OH plays a key role in the ORR catalytic process. For the both volcanos, CoP4 catalyst occupies the top owing to the moderate adsorption interaction between TMP4 and OER/ORR intermediates, thus performing the highest activity for the OER/ORR process with the minimum η OER (0.32 V) and η ORR (0.37 V). Therefore, the CoP4 can be regarded as the promising bifunctional OER/ORR electrocatalyst and better than IrO2 and Pt catalysts. The optimized stable structures of reaction intermediates adsorbed on CoP4 are displayed in Figure . Besides that, the electronic properties of all TMP4 catalysts were calculated to evaluate the reactivity and mechanism of bifunctional OER/ORR process. Figure and Figure exhibit the d-orbital DOS of the embedded TM atoms for different TMP4 systems. Previous reports have announced that the d-band center (Ed, obtaining from d orbital of TM atom) can be extensively used to furtherly expose the catalytic properties, therefore, which is labeled in the plots of d-orbital DOS (Figure and Figure ). Results suggest that, in the same period, the position of Ed will move toward to a more negative value relative to Fermi level with the increased d electron numbers of TM atoms, accordingly, causing the changed adsorption strengthen of every intermediate over TMP4 catalysts. Generally, the adsorption is weaker with a more negative Ed of TM atom, which can be explained by the hybridization between TM-d orbital and the electron states of adsorption species. As displayed in Figure , the hybridization of orbitals promotes the production of antibonding and bonding states. And the antibonding states are highly occupied when the Ed is located at a more negative value, which weakens the adsorption. Moreover, the high concentrations of d free electrons near Fermi level will devote rich electrons to reaction intermediates, resulting in the strong adsorptions and challenges for produce releasing (such as TiP4 system). In constant, the low d-electrons concentrations of catalysts could not maintain the effective adsorption of reaction intermediates (AgP4). Hence, for OER/ORR process, a suitable Ed position (a modest adsorption strengthen of intermediates) plays a key role for screening catalysts. In addition, Figure and In the last, the thermodynamic stability of CoP4 catalyst is then evaluated by AIMD simulations in the NVT ensemble (300 K). As shown in Figure and b, the energy and temperature oscillate near the initial values, and the structure of CoP4 is preserved well (Figure ) after 300 K dynamic simulation for 10 ps. Therefore, it can be concluded that the CoP4 serves as an efficient bifunctional OER/ORR catalyst with high stability. From the Figure , we observe stable phonon modes in this structure (without imaginary frequencies), revealing that the CoP4 is dynamically stable.