TiO2 photoelectrode has become an attractive platform due to its excellent photoelectric performance and has been widely used in battery, photocatalysis, and other photoelectric fields. However, when the TiO2 photoelectrode is used in solar flow batteries, the small photo-charging current is a potential problem, which will extend the charging process and lower the battery utilization efficiency. To address this issue, Cu2O is introduced to the surface of the TiO2 photoelectrode, and Cu2O-TiO2 forms a heterojunction to improve battery performance in this work. The formation mechanism of Cu2O-TiO2 is revealed and utilized to deposit Cu2O on pre-treated FTO glass covered with TiO2 films using electrochemical deposition (ECD). The photoelectrochemical properties of Cu2O-TiO2 photoelectrodes are characterized using XRD, UV-vis diffuse reflectance spectroscopy, XPS, and electrochemical characterizations. The successful deposition of Cu2O on the surface of TiO2 photoelectrode is confirmed, and the UV-vis spectroscopic test results show that the incorporation of Cu2O enhances and broadens the absorption and utilization of sunlight in the UV range by the TiO2 photoelectrode. Furthermore, the electrochemical test results manifest that the Cu2O-TiO2 photoelectrode possesses a higher carrier concentration under illumination conditions due to the formation of a heterojunction. Finally, a 30 min unbiased photocharging test demonstrates that the Cu2O-TiO2 photoelectrode charges in a current density of 425.03 μA·cm−2, indicating an increased photogenerated carrier concentration and a decreased photogenerated carrier recombination rate, which results from the enlarged doping concentration and improved charge transfer process at the electrolyte/semiconductor interface due to the incorporation of Cu2O. Compared with the current density of 116.21 μA·cm−2 for the bare TiO2 photoelectrode, the performance can be improved by over 365%.