Short thermal treatment of carbon felts for copper-based redox flow batteries

Carbon felts are often used aselectrode materialsfor variousredox flow batteries(RFBs), and for optimal performance it is often required for them to be subjected to extended thermal treatment processes (25–30h). However, the Cu(II)/Cu(I)redox coupleemployed in the copper RFB, at thepositive electrodeis significantly different when compared to the vanadium alternative. For this reason, the effect and duration of thermal treatment of the carbon felt on the performance of the copper-based RFB has to be determined. Both polyacrylonitrile and rayon carbon felts were subjected to thermal treatment for 6 and 25h at 400°C. The treated carbon felts were subsequently analysed usingthermogravimetric analysis, resistivity determination, scanning electron microscopy, X-ray photoelectron spectroscopy, andRaman spectroscopy. Additionally, the effect of the thermal treatment was also determined using electrochemical testing and in a redox flow cell.