The ΔG is usually defined by: ∆G = ∆E + ∆ZPE -T∆S [7] Here, ∆E represents the total energy difference for the adsorbed HER or OER intermediates obtained from DFT calculation, ∆ZPE is the change of zero-point energy (ZPE), and T∆S denotes the influence of change in entropy, typically at ambient temperature (298K). Both the ZPE and entropies of HER and OER intermediates can be calculated based on the harmonic approximation to nuclear vibrations. Since the equilibrium potential for HER and OER is 0 and 1.23 V vs. SHE, respectively, the OP can be calculated as OPHER = max{ΔG1 , ΔG2}/e, and OPOER = max{ΔG3 , ΔG4, ΔG5, ΔG6}/e-1.23 V. ΔGi (i=1,2,3...) represents the free energy change of the electron-involved elementary steps of HER and OER as shown above. Computationally, the carrier mobility can be evaluated by employing the acoustic phonon-limited scattering model based on deformation potential theory . The GGA-PBE functional, which in most implementations performs much faster compared to hybrid functionals, was demonstrated to be sufficient to predict very similar effective masses and carrier mobilities compared to those calculated by HSE06 . This can be understood as the band shapes calculated by PBE typically are very similar to those computed at higher levels of theory, even though the conduction bands are shifted to lower values, which results the well-known band gap underestimation of PBE and other local functionals. As consequence, the costly calculation of electron and hole mobilities can be performed using local functionals such as PBE. However, due to the fact that the synthesized 2D polymers usually contain defects or impurities, the experimental carrier mobilities typically are inevitably lower than the computationally predicted values.