When the BiVO 4 electrode immersed in an aqueous electrolyte, the protonation or deprotonation of surface groups depends on their pK a values and pH in solution. There is a special pH at which the concentration of H + on the surface equals that of OH -, i.e., the point of zero charge (PZC). PZC can be measured by the potentiometric titration method and electrochemical in situ spectroscopy technologies. However, the intrinsic pK a values of individual surface groups are typically unable to characterize by experiments. Herein we first calculate the acidity of the individual adsorption sites on BiVO a (010)/NaCl interface from DFTMD, by applying harmonic restraining potentials V rH to all O-H bonds (see Table †) . Detailed descriptions of the computational setup are given in the ESI. † At the BiVO 4 (010) surface, there are two types of surface sites capable of protonation or deprotonation (see Fig. ): the hydroxylated 7-fold coordinated Bi groups and the bridging oxygen O br connecting Bi and V groups Bi 7f OH 2 → Bi 7f OH -+ H + (aq), pK a1