Multi-Strategy Catalysis of Mn-TiO2/TiO2 Composite Photoanode with Built-In Electric Field to Enhance the Charging Performance of Solar Flow Batteries

The synthesis of Mn-TiO2/TiO2, together with its application as a photoanode for solar flow batteries (SFBs), is reported herein. Both the pure TiO2electrode and the Mn-TiO2/TiO2based composite electrode were prepared using the sol–gel spin-coating technique. The incorporation of a Mn-TiO2layer led to the enhancement of the built-in electric field within the composite photoanode. This enhancement not only improved the light-harvesting capability of the photoanode but also suppressed the recombination of charge carriers, consequently enhancing the photocatalytic efficiency. Furthermore, the optimal annealing temperature and the optimum TiO2loading were systematically controlled and optimized to maximize the photoelectric conversion efficiency of the composite photoanode. Ultimately, the optimized Mn-TiO2composite photoanode was integrated into a monolithic solar flow battery. The results demonstrate that the battery’s photocharging current density reaches 300 μA·cm−2. The photocharging current density was relatively increased by 150%.