In relatively simple PEC water splitting devices, such as Fe2O3 photoanodes, several models describing various processes and material properties have been established (e.g. charge transfer to the electrolyte, charge trapping and detrapping, and the presence of surface states). However, in a complex multi-layered PEC system such as a TiO2-protected buried junction photocathode with hydrogen evolution catalyst, in-depth studies providing EIS data with elaborate verification of the corresponding EC model has hardly been reported. Our group previously demonstrated that a resistance-based method using EIS (i.e. considering only the resistances from the EC model) can be used as a tool for identifying the limiting interfaces in Cu2O and Si-based multi-layered photocathodes. Despite the simplicity and power of the resistance-based method, additional information obtainable from the EC elements, such as the capacitances and time constants, should be taken into account to fully exploit the advantages of the EIS method.