Experimental identification of CO2 adsorption sites in TiO2 nanocrystals reveals distinct surface environments, suggesting implications for catalytic processes.
Facet-dependent surface oxygen environments play a central role in adsorption and catalytic processes on oxide nanocrystals, but their direct experimental identification remains challenging. Here, we employ 17O and 13C magic-angle-spinning solid-state NMR spectroscopy to investigate three anatase TiO2 nanocrystals predominantly exposing (001), (101), and (111) facets. The 17O NMR spectra reveal distinct facet-dependent surface oxygen environments, including low-coordinated surface O2c species, near-surface O3c species, hydroxyls, and adsorbed water. DFT calculations further support the assignment of the oxygen species and indicate that the hydrated A-TiO2-111 surface is best described by a model containing both dissociatively and molecularly adsorbed water. Upon CO2 adsorption, combined 17O and 13C NMR results show that surface O2c species are the dominant adsorption sites on all three facets, whereas differences in the involvement of hydroxyl and water species lead to distinct carbonate-to-bicarbonate distributions. These results provide an atomic-level picture of facet-dependent CO2 adsorption on anatase TiO2 nanocrystals.
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Zhang et al. (2026) studied this question.
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