Polyacrylonitrile (PAN)-based carbon felts with different fibre properties were studied in terms of their suitability as porous flow-through electrode materials in all vanadium redox flow batteries. The crystallinity and their bulk hetero element content (in particular nitrogen) of the carbon fibres was shown to produce a significant effect on the electrocatalytical properties of the electrodes towards vanadium species. Similar effects were seen on the capacity losses associated with concomitant hydrogen evolution. Adjustments of fibre properties offer the potential of manufacturing improved electrode materials, potentially without additional steps such as surface activation or decoration with catalytically active species.