Outside-to-inside: Efficacy comparation of Mn bulk and surface-doped TiO2{201} in E-fueled solar flow battery system

The all-in-one E-fueled solar flow battery system that can be recharged with liquid fuel is a new type of power system. It can continuously convert solar energy into liquid fuel without relying on external power supply equipments. However, the interface between the photoanode and the electrolyte often exhibits unsteady behavior, resulting in poor performance of the system. In this work, the {201} facets are selected and the impact of two doping treatment strategies for TiO2 {201} photoanode on the performance of the E-fueled solar flow battery system is systematically studied through the I-t curve, linear sweep voltammetry, Mott-Schottky plot. The results show that the un-biased photocharging current of bulk-doped TiO2 can reach 2.7 mA⸱cm−2 in the battery system test, only relying on the self-built electric field at the interface, and the energy conversion efficiency approaches 2.67%. In addition, the performance is analyzed by the combination of transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and other characterizations, with the aim of distinguishing the effects of bulk- and surface-doped Mn and accurately revealing the mechanism of their influences from the outside to the inside. Finally, the optimization rules of the un-biased light charging mode of the system are explored.