Efficient harvesting and storage of solar energy of an all-vanadium solar redox flow battery with a MoS2@TiO2 photoelectrode

Abstract

Solar redox flow batteries constitute an emerging technology that provides a smart alternative for the capture and storage of discontinuous solar energy through the photo-generation of the discharged redox species employed in traditional redox flow batteries. Here, we show that a MoS₂-decorated TiO₂ (MoS₂@TiO₂) photoelectrode can successfully harvest light to be stored in a solar redox flow battery using vanadium ions as redox active species in both the catholyte and anolyte, and without the use of any bias. The MoS₂@TiO₂ photoelectrode achieved an average photocurrent density of ∼0.4 mA cm⁻²versus 0.08 mA cm⁻² for bare TiO₂, when tested for the oxidation of V⁴⁺ to V⁵⁺, attributed to a more efficient light harvesting and charge separation for the MoS₂@TiO₂ relative to TiO₂. The designed solar redox flow cell exhibited an optimal overall solar-to-output energy conversion efficiency (SOEE) of ∼4.78%, which outperforms previously reported solar redox flow batteries. This work demonstrates the potential of the MoS₂@TiO₂ photoelectrode to efficiently convert solar energy into chemical energy in a solar redox flow battery, and it also validates the great potential of this technology to increase reliability in renewable energies.