The development of solar energy conversion in the production of fuels, water splitting and water purification systems, has become an important sidestep for traditional fossil energy. Herein we have investigated the coupling effect of a Photo-Fenton system on a conventional photocatalytic reaction with a novel Fe doped C3N4/WO3 hybrid structure. The decomposition of p-nitrophenol was selected as a model reaction in the context of the degradation of organic pollutants. Heterojunction nanocomposites consisting of g-C3N4 nanosheets and WO3 nanoparticles were shown to facilitate the separation of photo-induced electron and hole pairs. The photocatalytic activity was further maximized as a result of a synergism of the 'Photo-Fenton cycle' with Fe(II) or Fe(III)-doping in the presence of H2O2 to generate additional hydroxyl radicals. As a result, after 4h under visible light the degradation of p-nitrophenol could be remarkably enhanced from 10 to 90% compared to the g-C3N4 reference. To the best of our knowledge, this is the first time such a striking increase is reported with a Photo-Fenton system applied in the present photocatalytic system. The significance of the presence of hydroxyl radicals in the photo-Fenton performance of Fe-doped C3N4/WO3 was assessed by scavenger and fluorescence tests. Additional light was shed into the reaction mechanism via spin trapping enabled by in-situ electron paramagnetic resonance. (C) 2017 Elsevier B.V. All rights reserved.