## 4 Conclusions
The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app131910591/s1](https://www.mdpi.com/article/10.3390/app131910591/s1)]([https://www.mdpi.com/article/10.3390/app131910591/s1](https://www.mdpi.com/article/10.3390/app131910591/s1)), Section S1: Different aspects regarding ex situ and in situ materials synthesis methods, Section S2: light source for photocatalysis experiments, Section S3: characterisation of g-C\({}_{3}\)N\({}_{4}\) bulk and Section S4: FeOx composite films, Section S5: supporting information for photocatalytic tests, Section S6: Raman peak assignments, and Section S7: UV-Vis spectra from the photocatalysis experiments. Figure S1: Measured and normalized spectrum of visible light lamps (75 W each) employed in this work (Osram HALOPAR 30, 75 W, 30\({}^{\circ}\) aperture angle, luminous flux of 350 lumers); Figure S2: Absorption spectrum of melamine used as precursor to g-C\({}_{3}\)N\({}_{4}\) synthesis; Figure S3: SEM image of g-C\({}_{3}\)N\({}_{4}\) powder synthesized at 550 \({}^{\circ}\)C 4h and its corresponding EDXS spectra; Figure S4: FTIR spectra of the melamine and g-C\({}_{3}\)N\({}_{4}\) synthesized at 550 \({}^{\circ}\)C 4 h; Figure S5: Raman spectra of melamine and g-C\({}_{3}\)N\({}_{4}\) synthesized at 550 \({}^{\circ}\)C 4 h; Figure S6: GIXRD pattern of the synthesized g-C\({}_{3}\)N\({}_{4}\) powder at 550 \({}^{\circ}\)C; Figure S7: UV-Vis absorption spectra and Tauc plot of the g-C\({}_{3}\)N\({}_{4}\) synthesized at 550 \({}^{\circ}\)C 4h; Figure S8: EDXS spectrum of the surface of the FeOx urchin like structures used as support in the composite with g-C\({}_{3}\)N\({}_{4}\); Figure S9: EDXS spectra from 4 different regions of the (FeOx/g-C\({}_{3}\)N\({}_{4}\))_in_ composite thin films; Figure S10: EDXS spectra from two different regions of the (FeOx/g-C\({}_{3}\)N\({}_{4}\))_ex_ composite thin films; Figure S11 (FeOx/g-C\({}_{3}\)N\({}_{4}\))_in_ TEM image and corresponding larger area SAED pattern; Figure S12: XPS spectra of (a) Fe 2p (top left) and specifically Fe 2p\({}_{3/2}\) (top right) and (b) O1s core levels without curve fitting of the iron urchin and its composites with g-C\({}_{3}\)N\({}_{4}\); Figure S13: Removal yields of the CIP disappearance upon irradiation of g-C\({}_{3}\)N\({}_{4}\) 4h in powder (black) and in the film (blue) in aqueous solutions containing CIP (C\({}_{0}\) = 10 ppm); Figure S14: Removal yields of the CIP disappearance upon irradiation of (FeOx/g-C\({}_{3}\)N\({}_{4}\))_ex_ thin films immersed in aqueous solutions containing CIP (C\({}_{0}\) = 10 ppm); Figure S15: Control experiments: aerated aqueous solution of CIP (10 ppm) maintained at 50 \({}^{\circ}\)C in the dark (red) or visible irradiated (blue) in the absence of any photocatalyst; Table S1: The modes of every peak identified in the Raman measurements. The peaks identifications are based on the literature [100; 101; 102; 103]; Figure S16: UV-Vis spectra from obtained from the photocatalysis and photo-Fenton experiments. Conceptualisation: M.F., O.P.B. and M.O. ; sample preparation and analysis: M.F., O.P.B., R.E., A.M. ([PERSON]), P.R. and C.M. ; original draft preparation: M.F. and O.P.B. ; writing--Review and editing: M.O., A.M. ([PERSON]), A.M. ([PERSON]), R.E. and C.M. ; supervision: M.O. and A.M. ([PERSON]); funding acquisition: A.M. ([PERSON]) and M.O. All authors have read and agreed to the published version of the manuscript. This work was supported by the ERICSOL project, funded by the University of Trento, and by the FarSol project, funded by the Caritro Foundation (Research & Development 2020 Grant). We also acknowledge project \"Produrre Idrogeno in Trentino--H2@TN\" (PAT-Trento). [PERSON] and [PERSON] acknowledge project FUN-FACE (SID_2019) of the Physics and Astronomy Department of the University of Padova (Italy). Not applicable. **Data Availability Statement:** Raw data or datasets not included here are available from the authors upon request. We thank [PERSON] for SEM/TEM measurements and [PERSON] for FT-IR support.