In this study, we explore the charge transfer mechanism between CuWO4 and
CuBi2O4 in a tandem photoelectrochemical cell. Physical–chemical characterization of the individual between CuWO4 and CuBi2O4 electrodes electrode by XRD, XPS, and SEM methods confirm the successful formation of the target systems. Based on XPS and DRS data, the electronic band edge positions were estimated (valence bands: −6.1 eV and −5.6 eV; conduction bands: −3.7 eV and −3.8 eV for CuWO4 and CuBi2O4, respectively), indicating that both type II and Z-scheme charge transfer mechanisms are possible in the system. The results of photoelectrochemical studies infers that, in a CuWO4||CuBi2O4
tandem photoelectrochemical cell, the major mechanism of the charge transfer between CuWO4 and CuBi2O4 is a realization of Z-scheme through an external circuit.