Researchers at China’s Nanjing Tech University (NanjingTech) have developed a novel solar redox flow battery (SRFB) that achieves an average solar-to-electricity conversion efficiency of 4.2%. The device combines an anthraquinone-based electrolyte with a triple-junction solar cell, creating an integrated system that captures sunlight and stores energy in a single unit.
What if a single device could capture sunshine and store it as chemical energy for on-demand use, all without the complex wiring between separate solar panels and batteries? That’s the promise of solar redox flow batteries, and a team in China has just pushed the technology forward with a new, more efficient design. Their integrated system sidesteps the corrosive pitfalls of earlier models, offering a streamlined path for converting and storing solar power.
The research, led by Nanjing Tech University and detailed by corresponding author Chengyu He in pv magazine, focuses on a clever pairing of materials. The system uses an aqueous organic anthraquinone derivative known as 2,6-DBEAQ paired with K4[Fe(CN)6] as its redox couples—the chemical workhorses that shuttle electrons during charging and discharging. These flow through the device, separated by a Nafion ion-exchange membrane, and interact with a photocathode made from a commercially sourced triple-junction amorphous silicon (3jn-a-Si) solar cell.
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Why this combination? As Chengyu He explained, earlier anthraquinone-based systems often operated in highly acidic or alkaline conditions, which degraded the photoelectrodes and limited efficiency. The new formulation offers better compatibility. “The successful preparation of this SRFB device opens up new possibilities for the further development of advanced solar-to-chemical energy conversion technologies,” He stated. During testing, reported in the journal Electrochimica Acta, the device was photo-charged under a xenon lamp simulating 1-sun intensity and discharged over multiple cycles.
The process is elegantly integrated. When sunlight hits the 3jn-a-Si photocathode, it generates electricity that directly drives the chemical reactions. The 2,6-DBEAQ in the catholyte is reduced, storing energy, while the K4[Fe(CN)6] in the anolyte is oxidized at a carbon felt electrode. The electrolytes are pumped from external tanks, allowing for easy scaling of energy capacity simply by using larger storage vessels. In a key cyclic test, the device maintained its performance over 10 charge-discharge cycles, achieving a peak efficiency of 4.3%.
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This 4.2% average efficiency mark, while modest compared to stand-alone photovoltaic cells, is significant for an integrated capture-and-storage device. It represents a tangible step toward practical, solar-charged batteries for decentralized applications. The work, supported by the research team at Nanjing Tech University, demonstrates that by carefully selecting stable, compatible materials, the dual goals of conversion and storage can be efficiently combined in one apparatus, potentially simplifying future solar energy systems.
