Regulating SnO2 surface by metal oxides possessing redox or acidic properties: The importance of active O2−/O22− and acid sites for toluene deep oxidation

The Key Role of Active Sites in the Development of Selective Metal Oxide Sensor Materials

“…The oxide anions can be determined by X-ray photoelectron spectroscopy (XPS). The asymmetric O 1s signal of nanocrystalline metal oxides can be simulated by two components (Figure 8): the major signal with binding energy 530.0-530.5 eV due to bulk O 2− anions and the lower peak of surface oxygen species at higher binding energy (531.0-533.0 eV) [34,85,86].…”

“…The oxidizing surface sites are most often associated with adsorbed oxygen [2,8,12,85,86,88,89]. There are several types of adsorbed oxygen species on a metal oxide surface: Besides, hydroxyl species were found to possess oxidizing activity to reducing gases: CO, H 2 [82,83,92].…”

“…One of the reasons is high electron affinity, instability and reactivity of atomic oxygen, which is believed to take place in oxidation reactions at the surface of catalysts and sensors [88,90,[163][164][165]. Molecular oxygen adsorbates can be detected by the vibrational stretching O-O peaks in the infrared spectral range 1050-1150 cm −1 [25,70,85]. However, this peak is broad and low-intense, since the vibration of non-polar adsorbed O 2 molecule has weak activity in the infrared spectra.…”

The critical roles of hydrophobicity, surface Ru0 and active O2−/O22− sites on toluene combustion on Ru/ZSM-5 with varied Si/Al ratios

“…It was reported in the literature that the capability of a catalyst to adsorb and activate toluene molecules can impact its oxidation activity greatly. 46,47 Hence, toluene-TPD was performed to identify the toluene adsorbing capacities of the catalysts. To exclude the effect of oxygen desorbing, the catalysts were treated first in an Ar flow (99.99%) at 400 °C for 30 min to eliminate the initially adsorbed oxygen anions.…”

Doping SnO2 with metal ions of varying valence states: discerning the importance of active surface oxygen species vs. acid sites for C3H8 and CO oxidation

“…Due to its abundant lattice and surface defects/vacancies, tetragonal rutile SnO 2 , as an n-type semiconducting oxide, finds applications in gas sensors, solar cells, semiconductor devices, and electrode materials. 21–23 Previous investigations have validated that the surface defect enables the adsorption and activation of gaseous O 2 , thus resulting in the generation of abundant active O 2 − and O 2 2− sites, 24–26 whereas these surface oxygen species on pure SnO 2 can be relinquished when calcined at temperatures exceeding 300 °C, which thus limits its redox property and reactivity. 27,28 The incorporation of secondary metal ions in the SnO 2 matrix has been reported to effectively stabilize the surface-active oxygen sites.…”