Synergistically enhanced photocatalytic activity of graphitic carbon nitride and WO₃ nanohybrids mediated by photo-Fenton reaction and H₂O₂

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/WO₃hybrid 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-C₃N₄nanosheets and WO₃nanoparticles 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 H₂O₂to generate additional hydroxyl radicals. As a result, after 4 h under visible light the degradation of p-nitrophenol could be remarkably enhanced from 10 to 90% compared to the g-C₃N₄reference. 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/WO₃was assessed by scavenger and fluorescence tests. Additional light was shed into the reaction mechanism via spin trapping enabled by in-situ electron paramagnetic resonance.