Comment on “A 'one pot' gel combustion strategy towards Ti³⁺ self-doped 'black' anatase TiO_2-x solar photocatalyst,” by S. G. Ullattil and P. Periyat, J. Mater. Chem. A, 2016, 4, 5854

In this work, it is shown that the high concentration of Ti³⁺ in “black” anatase TiO_2-x, as claimed by Sanjay Gopal Ullattil et al. [Sanjay Gopal Ullattil et al., J. Mater. Chem. A, 2016, 4, 5854-5858], is inappropriate. Using the binding energy difference parameter ΔBE = BE(O 1s) - BE(Ti 2p_3/2) = 528.7 - 457.6 = 71.1 eV, the domination of the Ti⁴⁺ state in the considered compound is verified.