Probe-Molecule-Assisted NMR Spectroscopy: A Comparison with Photoluminescence and Electron Paramagnetic Resonance Spectroscopy as a Characterization Tool in Facet-Specific Photocatalysis

Photoluminescence (PL) and EPR spectroscopy are the two most commonly used techniques to evaluate surface oxygen vacancies (V_{O surface}) on photoactive transition metal oxides. However, these techniques have shortcomings in the characterization of facet-dependent catalysis. Here, we used the chemical adsorption of a ³¹P-containing probe molecule to obtain the distribution/concentration of V_{O surface} as well as other surface features (hydroxyl groups) of ZnO by using ³¹P magic-angle spinning NMR spectroscopy. This facet-specific technique not only makes cross-literature comparison feasible but also provides more comprehensive information to lead to a further understanding of the photocatalytic mechanism.