One of the main reasons for the high levelized cost of storage of a Redox Flow Battery (RFB) is its low power density. This, in turn, is mainly determined by redox reaction kinetics at the electrodes. There are two possible solutions to increase the power density: (i) increasing surface area, or (ii) increasing reaction kinetic. Carbon felt (CF) offers a good trade-off between these requirements, setting a benchmark for most industrial batteries. Nevertheless, running a RFB at high current density, i.e. high power density, the elevated ohmic resistance of CF cannot be neglected. On the other hand, Carbon Paper (CP) offers a lower ohmic resistance and mass transport hindrance, but it still cannot compete with the CF. X-nano developed a unique hierarchical electrode comprising a mesoporous assembly of turbostratic carbon nano onions (T-CNO) on the fibres of carbon paper or cloth electrodes. The X-nano electrode enables to obtain high current density in a flow battery hence decreasing stack dimension, costs, and auxiliary power. Uniform coverage of the fibres is ensured by a proprietary deposition method, called NanoJeD, which, starting from the gas phase, offers a high throughput, dry, agile, and easily scalable process. NanoJeD system consists of a fluxed radiofrequency plasma operating in dusty mode; the gas is a mixture of argon-acetylene and the plasma ignites the decomposition and clusterization of acetylene, forming hydrogenated carbon nanoparticles (H-CNP). The H-CNP are dragged through a high aspect ratio orifice and ejected in a low-pressure chamber. NPs are collected on the substrate by inertial collisions. A vacuum thermal treatment at 1000°C is performed to the electrode in order to convert the hydrogenated carbon nanoparticles to T-CNOs and enhanceing the electrode mechanical stability. The resulting film has a surface area of 350 m2g-1. Catalytic properties of T-CNO were tested by cyclic voltammetry and by electrochemical impedance spectroscopy, showing a dramatic increase of the catalytic activity of the film. Symmetric cell test reported a current density sixfold higher than the untreated carbon paper operating at the same overpotential. Combining the obtained high surface area with the high catalytic activity we reached in a full cell, a current densities up to 400 mAcm-2 and 600 mAcm-2, with 81% and 74% energy efficiency of respectively. An electrolyte utilization of 70% was measured at 400 mAcm-2. Stability tests showed a low degradation rate, losing less than a 0.004% energy efficiency per cycle in over 1000 cycles.