<p>Scaling up carbon-based electrodes for hydrogen peroxide electro-production remains challenging despite promising laboratory-scale results. In this study, a sulfuric acid modification method was successfully scaled up from a 25&#xa0;cm² to a 200&#xa0;cm² graphite fiber felt electrode. Surface modification was confirmed by scanning electron microscopy, cyclic voltammetry, rotating disk electrode, and X-ray photoelectron spectroscopy analyses. Electrochemical performance was evaluated under varying flow rates, current densities, and residence times in batch and continuous flow modes. The increased electrode size required a higher acid concentration for effective modification. In both flow modes, hydrogen peroxide concentration increased with current density up to 1.5&#xa0;mA cm^-², beyond which yields declined. At this current density and a Reynolds number of 770, maximum hydrogen peroxide concentrations of 32.8 mg L^-1 (batch) and 11.2 mg L^-1 (continuous) were achieved, with corresponding current efficiencies of 30% and 50%. In batch mode, hydrogen peroxide concentration increased linearly with Reynolds number, reaching 39.8 mg L^-1, while in continuous flow, prolonged residence time increased hydrogen peroxide to 22.1 mg L^-1 at 21&#xa0;min, followed by a slight decline. The electrode exhibited stable performance over ten 110-min cycles and up to 385 residence times. These results demonstrate the feasibility and operational viability of sulfuric acid-modified graphite fiber felt cathodes for practical hydrogen peroxide electro-production.</p> Graphical Abstract <p></p>