A non-aqueous thermally regenerative flow battery using reduced graphene oxide-modified nickel foam electrodes for low-temperature heat harvesting

Low-temperature geothermal energy (<150 degrees C) is an abundant green renewable energy and non-aqueous thermally regenerative flow batteries hold immense potential for converting it into electricity. In this study, a reduced graphene oxide-modified nickel foam (RGO/NF) was developed to promote the battery performance. It was demonstrated that the low-cost nickel foam with extensive optimization potential was the desired substitute for the traditional reticulated glass carbon electrode, with a similar maximum power density (105.7 W/m2). With acid treatment, a relatively rough surface with increased specific surface area was obtained, resulting in an improved performance of the battery. According to the density functional theory results, the modification of RGO on NF provided a strong microscopic interaction with Cu, accompanied by more active sites and improved wettability. Therefore, the maximum power density of the battery was increased by 21 %, while the capacity was extended by 100% and the energy density was improved by 165 %, compared to the battery with NF. To further improve the battery performance, the flow rate and mass fraction of nano copper were optimized, exhibiting the optimal values of 35 mL/min and 15%, respectively. The present results were competitive and helpful for future application of this technology for low-temperature geothermal energy recovery.