Operation of vanadium redox flow batteries at low (below 5^◦C) and high (above 40^◦C) temperatures presents a significant challenge for commercialization due to issues with the solubility of vanadium under these conditions. One strategy that has been developed is the use of a mixed sulfuric and hydrochloric chloride acid electrolyte to stabilize the vanadium species. In this study, the electrochemical characteristics of the mixed acid system was explored using cyclic voltammetry at low and high temperature, with a range of electrode materials, including carbon paper, graphite felt and nanoporous carbon scaffold (NCS). Scanning electron microscopy (SEM) was used to characterize the morphology of the electrodes materials. The results show that the mixed acid system stabilized the vanadium redox system and enable operation at higher concentrations, leading to significant improvement in electrochemical characteristics at low and high temperature. Also, NCS electrode materials were found to have higher activity than graphite paper and graphite felt for the vanadium redox systems in the mixed acid electrolyte.