Effect of altervalent cation-doping on catalytic activity of neodymium sesquioxide for oxidative coupling of methane

Identifying Surface Active Sites of SnO2: Roles of Surface O2–, O22– Anions and Acidic Species Played for Toluene Deep Oxidation

“…As displayed in Figure A, all of the catalysts show four Raman peaks at 476, 570, 634, and 777 cm –1 . The 476, 634, and 777 cm –1 peaks are assigned to E g , A 1g , and B 2g vibration modes of rutile SnO 2 , respectively, which belong to the space group of D 14 4h , , whereas the A 1 band at 570 cm –1 is reported to be related to the surface oxygen vacancies of SnO 2 , whose amount can influence the formation of surface active oxygen sites. ,− In detail, the gas-phase O 2 molecules can be adsorbed on the vacancies, which obtain electrons from the neighboring lattice O 2– species to generate electrophilic oxygen species, such as O 2 – and O 2 2– . − A 1 /A 1g , the integrated area ratio between the A 1 and A 1g peaks, has been used to estimate the amount of the surface defects of SnO 2 previously. ,, Therefore, the A 1 /A 1g ratios of all of the SnO 2 samples are quantified and exhibited in Figure B. Interestingly, the quantities of the surface oxygen vacancies increase in the order SnO 2 -Pre < SnO 2 -Mic ≪ SnO 2 -Stir-OH < SnO 2 -Ultra-OH, which fits well to the overall and intrinsic activities of the catalysts.…”

“…Interestingly, the quantities of the surface oxygen vacancies increase in the order SnO 2 -Pre < SnO 2 -Mic ≪ SnO 2 -Stir-OH < SnO 2 -Ultra-OH, which fits well to the overall and intrinsic activities of the catalysts. It has been commonly accepted that the existing of surface oxygen defects can benefit to the formation of surface active electrophilic oxygen species, − which might favor toluene deep oxidation.…”

“…As quantified in Table S2 and depicted in Figure B, compared to SnO 2 -Pre and SnO 2 -Mic, SnO 2 -Ultra-OH and SnO 2 -Stir-OH possess obviously far bigger amount of both surface loosely bonded (α + β) and active surface lattice oxygen (γ) species, which is in line with the catalytic activity of the catalysts and well consistent with the H 2 -TPR results. The generation of more abundant active surface oxygen sites could be related closely to the specific surface areas and surface defects of catalysts, as it has been proved above by Raman spectroscopy that a sample with a higher specific surface area usually possesses more surface defects, which improves a catalyst’s ability to adsorb and activate oxygen molecules, − and in the end enhances the activity of the samples.…”

“…On the basis of in situ DRIFTS and EPR results, and the basic rules for XPS peak deconvolution, the asymmetric O 1s peak could be divided into three symmetrical peaks at around 530.7, 531.5, and 532.9 eV, which correspond to surface lattice O 2– , peroxide O 2 2– , and superoxide O 2 – species, respectively. ,, As mentioned while discussing the Raman results, all of the SnO 2 samples possess surface oxygen vacancies, which are extremely open. As a result, the gas-phase O 2 molecules can enter into the vacancies to form abundant active surface electrophilic oxygen species, such as O 2 – and O 2 2– . − Through this pathway, surface active oxygen species can usually be produced, whose quantity is decided by the amount of surface vacancies and defects.…”

NdCl3 Dose as a Universal Approach for High-Efficiency Perovskite Solar Cells Based on Low-Temperature-Processed SnOx

“…In the high-resolution XPS spectra, the three subcomponents of Sn(IV)−O, Sn(II)−OH, and Nd(III)−OH bonds, located at 531.0, 532.0, and 532.3 eV, could be distinguished from the O 1s state 37,39,40 (Figure 2c−d and Table 1). The existence of Sn(II)−OH in both c-SnO x and SnO x :NdCl 3 films could also be identified by FT-IR analysis.…”