Iron/Quinone-based all-in-one solar rechargeable flow cell for highly efficient solar energy conversion and storage

In recent years, extensive efforts were made to develop solar rechargeable flow cell (SRFC) for the capture, conversion, storage and distribution of intermittent solar energy. However, the performance of most SRFCs is far from being satisfactory and the working mechanisms are not well understood. In this work, an all-in-one SRFC (ASRFC) with Fe/AQDS redox couples and an amorphous silicon (aSi) based photoanode is designed and constructed. Originating from the fast kinetics of Fe³⁺/Fe²⁺ [k⁰’=(9.0 ± 0.1) × 10⁻³ cm s⁻¹] and AQDS/AQDSH₂ [k⁰’=(1.4 ± 0.1) × 10⁻² cm s⁻¹] together with the efficient light harvesting and charge separation of the aSi, the optimal solar-to-chemical conversion efficiency of the Fe/AQDS-based ASRFC reaches 6.5%, indicating 93% of solar energy converted by the aSi-based photoanode can be stored in the redox couples. Moreover, a record photoelectrode utilization efficiency of 70% demonstrates the well-matched energy-level between the aSi-based photoanode and the Fe/AQDS redox couples. And this is a key factor in achieving an overall solar-chemical-electricity conversion efficiency of 4.9%, which outperforms previous published SRFCs operating in air atmosphere. These results may light up the path of developing efficient solar rechargeable devices for practical solar energy utilization.