With respect to the Figure , where we show spectra normalized over the whole energy range (450 -740 eV), here we apply similar normalization, i.e. we subtract linear background in the pre-edge region and multiply the spectrum to match the post-edge, but limited to each elemental absorption region independently. We can thus focus on the electron structure comparison between samples. At Ti absorption edge, Figure , the S2 sample presents a spectral shape characterized by symmetrical B (Ti L 3 e g electronic transition) peak, likewise in ilmenite (FeTiO3) structure (Figure ). The relative intensities (branching ratio) between the A, B, C and D peaks, are equally characteristic to the Ti 4+ ion as expected for an ideal Ti substitution of the octahedrally coordinated Fe 3+ ion in the hematite (Fe2O3). Is important to note here that we do not measure ilmenite, since not getting the needed stoichiometry, but it can serve as surrogate to describe the local structure of the substitutional Ti-doping of the hematite structure. This local structure is probed by NEXAFS and is thus responsible for the specific spectral features. For the S1 sample the A:B branching ratio changes, the Ti L3 t2g band presents increased intensity compared to S2, while the C:D branching ratio is the same. The spectral shape is similar to TiO2 brookite structure. Considering the chemical information detailed above, we cannot consider TiO 2 alone at the surface of S1 sample. It is more reasonable to consider the pseudo-brookite structure, Fe1+xTi2-xO5, with x between 0 and 1. The corresponding crystallographic structures are represented in Figure . From the spectral shape it is impossible to obtain a particular value for x, since the Ti 4+ ion has the same octahedral coordination (Ti-O6) over the entire x range, from 0 to 1. Additional information can be extracted from the NEXAFS Fe spectra in Figure . First, we remark that, contrary to what one would expect, the S2 sample presents slight reduction of the Fe 3+ , the B spectral line is shifted toward lower binding energies by < 0.1 eV with respect to the S1 sample. This leads also to a variation of the d-orbital splitting, 𝑡 2𝑔 -𝑒 𝑔 (A-B), from 1.48 eV for S1 to 1.41 eV for S2. Such behavior is related to distortions of the Fe-O6 octahedra very close to the hematite nanoparticles surface and the Ti substitution in the hematite structure. Since S1 sample presents increased Ti content toward the surface, this distortion is further accentuated. In addition to the structural origin of this behavior, we have to consider that in the presence of Ti substitution, part of the Fe 3+ from the hematite structure is replaced by Ti 4+ and iron is reduced (Fe 2+ ), following the charge conservation relation: 2 • 𝐹𝑒 3+ = 𝐹𝑒 2+ + 𝑇𝑖 4+ . Therefore, for the S2 sample, the slight iron reduction agrees with the spectral shape measured at Ti absorption edge (Figure ) and is related to formation of Ti-O6 octahedra upon Ti substitution of Fe. Conversely, S1 sample exhibits increased proportion of Fe 3+ , signature for the formation of the pseudo-brookite phase, Fe1+xTi2-xO5 with x = 1, 47 capable of holding high concentration of Fe 3+ oxidation state from charge equilibrium criteria, in agreement with the NEXAFS spectra recorded at Ti edge (Figure ). Unfortunately, the literature lacks extended reports of pseudo-brookite NEXAFS at the Fe L2,3 absorption edge for further comparison. Lv et al. reported Fe L2,3 NEXAFS measurements recorded in total electron and fluorescence yield modes, for either coating or incorporated Fe2TiO5 into hematite. They evidenced only Fe 3+ related to the formation of the pseudo-brookite phase. A second notable feature that can be extracted from the Fe L2,3 NEXAFS, is the variation of A:B branching ratio that has a value of 0.65, for S2, that is expected for hematite. To the contrary, S1 exhibits a value of 0.56, equivalent to an iron oxyhydroxide (e.g. goethite). The branching ratio is related in first approximation to the Fe oxidation state.