Study on performance enhancement of electro-fueled solar flow battery system by nickel-doped titanium dioxide photoanode

Abstract

Integrated design of energy systems is a practical and economical solution to the low-carbon transition of international energy. In this work, a solar flow battery with electro-fuel is designed and assembled. The system directly converts solar energy into electro-fuel without biased electronic components, which is a reliable renewable energy utilization approach with low cost, low weight, and easy transmission. In the system, nickel-doped titanium dioxide photoanodes with different contents and annealing temperatures are prepared by the sol–gel method. The morphology, crystal structure and photo properties of the photoanodes are explored by various characterization methods. The performance of photoanode and the electro-fueled solar flow battery system is evaluated by the current–time curve, linear sweep voltammetry, Mott-Schottky plot, and other tests. The results show that 6% nickel doping annealing at 400 °C exhibits a higher photospontaneous charging current density. Only relying on the self-built electric field at the interface between the photoanode and the electrolyte, the photocurrent reaches 2.5 m∙cm−2, indicating the charge transfer rate at the photoanode-electrolyte interface is improved. The solar-chemical energy output efficiency achieves 2.51% without additional potential, which is higher than the current aqueous solar flow batteries. The photoanode-electrolyte interface was also further explored, and the energy level of nickel-doped titanium dioxide was quantified.