where L z is the dimension of the supercell perpendicular to the interface, q is the introduced surface proton charge, A is the area of the x, y cross section. P z indicates the ensemble averaged supercell polarization, which obtained from the averaged total dipole moment M z as shown in Fig. †. Accordingly, the value of C H for BiVO 4 /NaCl interface is calcualted as 77 µF/cm 2 . Based on the shift of macro-averaged electrostatic potential (∆φ ) with respect to the PZC (see Fig. ), the C + H and C - H are calculated as 74 µF/cm 2 and 77 µF/cm 2 , respectively (Table ).