This study systematically examines the effects of thermally treated porous electrodes in a single-cell vanadium redox flow battery on electrochemical performance and mass transport, combining experimental characterization with a two-dimensional numerical model that includes the membrane, porous electrodes, and current collectors. To analyze momentum, species, and charge transfer as well as the impact of flow rate variations, certain parameters of both commercial and thermally treated electrodes, including electrical conductivity, fiber diameter, and porosity, were experimentally measured, and these measured values were added to the numerical model. Numerical results show that the cell with the thermally treated electrode consumes less energy during charging and produces more energy during discharging than the cell with the commercial electrode. In addition, the thermally treated electrode exhibits a higher electrode/electrolyte potential and lower overpotentials. When the electrodes are separately compared for both the negative and positive sides, the variations of produced vanadium species concentrations with state of the charge and pressure distributions across does not change dramatically due to the minimal variation in porosity resulting from thermal treatment. Furthermore, it is revealed that the transport parameters vary significantly at low flow rates but they remain nearly constant at high flow rates.