Chinese researchers have developed an innovative solar redox flow battery (SRFB) capable of simultaneously harvesting sunlight and storing energy, achieving a solar-to-electricity conversion efficiency of 4.2 percent under simulated sunlight. The breakthrough comes from a team at Nanjing Tech University in Jiangsu province, who integrated light capture and energy storage into a single electrochemical system, eliminating the need for separate photovoltaic panels and conventional battery setups.
Unlike traditional solar systems, where sunlight is first converted into electricity and then stored, the SRFB directly triggers chemical reactions in a circulating electrolyte to store energy. This approach simplifies energy capture and opens new avenues for solar-to-chemical energy conversion.
The new SRFB relies on anthraquinone-based chemistry using redox couples 2,6-DBEAQ and K4[Fe(CN)6], paired with a triple-junction amorphous-silicon photoelectrode. Anthraquinone derivatives, widely recognized for their energy storage capabilities, are able to operate under acidic or alkaline conditions but have historically suffered from low efficiencies due to corrosion and instability. The Nanjing Tech team’s design improves chemical compatibility between the light-harvesting and storage components, enhancing performance.
The battery features compact 0.8-inch by 0.8-inch triple-junction amorphous-silicon–germanium photovoltaic cells coated with indium tin oxide (ITO) on stainless-steel substrates. These photocathodes are connected to carbon-felt counter electrodes via an external circuit. During operation, the photocathode interacts with the 2,6-DBEAQ catholyte, which reduces under illumination, while the anolyte K4[Fe(CN)6] oxidizes at the carbon-felt electrode. The two electrolytes circulate through the cell via external tanks and a peristaltic pump, separated by a Nafion ion-exchange membrane to prevent mixing and maintain charge balance.
Performance tests were conducted under a xenon lamp simulating sunlight at 100 milliwatts per square centimeter. The electrolytes were purged with argon to remove dissolved oxygen, and the battery was charged using light alone without any external electrical input. Discharging at a current density of 10 milliamperes per square centimeter over 10 cycles demonstrated a consistent solar-to-output electricity efficiency of 4.2 percent.
This SRFB represents a significant step forward in photoelectrochemical energy storage, offering a simpler, integrated alternative to conventional solar-plus-battery systems. The research team noted that the device’s success paves the way for further advancements in solar-to-chemical energy conversion, combining renewable energy capture with direct storage in one compact system. The study has been published in the journal Electrochimica Acta.
