Hi Benito,

>  The authors claim

>> The peak position for LTS-213 is approximately 4970 eV, which agrees well with that for rutile TiO2 with a valence of titanium species in the 4+ oxidation state.

> Should we use the pre-edge to determine the oxidation state? Is it reliable, or should we use E₀ and compare it with references of well-known oxidation states?

Many people use pre-edge peaks of transition metals for reliable analysis of metal oxidation states.   

E0 is sort of poorly defined term.  For the transition metals,  there will usually be a sharp rise in mu(E) at the energy of the metal’s own 4p electrons – the “main edge”, though this can sometimes be tricky to identify precisely, and sometimes has structure (as TiO2 does – slightly different for its different forms).

>> In addition, TiS2, in which titanium is also in the 4+ oxidation state, shows pre-edge peaks at 4968–4971 eV. (21) Considering the titanium oxidation state

>> in the raw materials, the stability of the titanium species, and the XANES results, the oxidation state of the titanium species in LTS-213 is likely to be 4+.

> The second conclusion is even more unclear.

What confuses me there is “TiS2 is in the 4+ oxidation state”.  Titanium disulfide is not oxidized at all - it is bound to sulfur.   Its charge state could be 4+, and many chemists use “oxidation” to mean the transfer of charge to and from a metal, whether this is done by oxygen or not.  For XANES, the ligand species matters.   K-edge XANES shows the energies of the unfilled p states at the center of the Ti atom, which will be very different for Ti-S (more covalent) and Ti-O (more ionic) bonds.