An organic-inorganic hybrid photoelectrochemical storage cell for improved solar energy storage

Abstract Greater levels of solar energy storage provide a promising path for sustainable and reliable utilization of the renewable energy source. One of the greatest challenges towards large-scale implementation of this technology is improving storage capacity and efficiency. The conventional solar-storage architecture, where rechargeable batteries and solar cells are externally coupled, typically results in addition of unnecessary efficiency and reliability margins in design, redundancy of resources (i.e. higher cost), and missed opportunities to increase performance through synergistic integration. Here we overcome these challenges by developing an organic-inorganic hybrid photoelectrochemical storage cell (PESC) to capture and store energy at the point of solar energy generation. The PESC was built by integrating a TiO 2 photoelectrode and a Quinone-Vanadium redox flow battery (RFB), which gives rise to superior photoelectrochemical reversibility and stability of the PESC. We demonstrated that photoelectron injection from the TiO 2 photoelectrode to the catholyte during unbiased photocharging was significantly enhanced by adjusting pH of the supporting electrolyte. The important charge separation at the semiconductor electrolyte interfaces was also analyzed through electrochemical and photoelectrochemical studies.