Fig. 2: Characterization and calculation for the conversion of surface OH to nearby O vacancy.
From: Active bridging hydride species in ZnO nanorods originated from hydroxyl and oxygen vacancy
a 1H NMR spectra of ZnO-300-vac and the ZnO-300-vac sample after being heated at 200 °C in a sealed glass tube under near-vacuum conditions (~50 Pa) (denoted as (ZnO-300-vac)−200) for 3 h. The 1H NMR spectrum of (ZnO-300-vac)-100 is also shown in Supplementary Fig. S12, together with those of ZnO-300-vac and (ZnO-300-vac)-200, in which a weaker resonance at 8.4 ppm is observed due to the lower extent of hydrogen migration at 100 °C compared to 200 °C. Note that the ZnO-300-vac was used to exclude the effects of water desorption on the origin of the resonance at 8.4 ppm during the heating process at 200 °C. Recycle delays of 5 s were used, and 64 scans were accumulated for the two spectra. b EPR spectra of ZnO-300-vac and (ZnO-300-vac)−200. The signal at g = 2.00 arises from unpaired electrons trapped in oxygen vacancies, the signal at g = 1.96 represents unpaired electrons trapped from the conductive band (CB) by shallow donors or impurities32. c The calculated models of ZnO nanorods used for the conversion of surface OH to nearby oxygen vacancy. Gray, red, and white spheres represent Zn, O, and H atoms, respectively. The dashed circles represent an oxygen vacancy.
