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. 2022 Dec 27;120(1):e2210211120. doi: 10.1073/pnas.2210211120

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Copyright © 2022 the Author(s). Published by PNAS.

This article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND).

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Fig. 4. — Chemical state and atomic local structure of TiO_x@C catalyst. (A) EPR spectra (77K) of TiO_x@C showing a clear surface Ti vacancy signal (g = 2.009) and a significantly weaker bulk Ti³⁺ signal (g = 1.946, Inset). (B) High-resolution XPS spectrum of Ti 2p. The percentage of valences of Ti element was calculated as Ti²⁺: 33.31%, Ti³⁺: 45.35%, and Ti⁴⁺: 21.34%. (C) Normalized Ti K-edge XANES spectra of Ti foil, TiO, Ti₂O₃, TiO₂, and TiO_x@C. (D) Estimation of the titanium oxidation state in TiO_x@C. According to the XANES spectra of Ti from the edge position of references to TiO, Ti₂O₃, and TiO₂, Ti was calculated to be in an average of 2.94⁺ oxidation state in TiO_x@C, with x = 1.47. (E) Normalized Ti K-edge XANES spectra of Ti foil, Ti₃AlC₂, Ti₃C₂, and TiO_1.47@C, respectively. (F) The k³-weighted FT spectra from Ti K-edge EXAFS.