Nanosized tin dioxide: Spectroscopic (UV–VIS, NIR, EPR) and electrical conductivity studies

Popescu, Daniela Amalric; Herrmann, Jean-Marie; Ensuque, Alain; Bozon‐Verduraz, François

doi:10.1039/b100553g

Cited by 102 publications

(35 citation statements)

References 18 publications

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“…The DRIFT spectra taken of the pure SnO 2 sample were in line with this mechanism ( Figure 10 a). There were decreasing bands visible at 1060 cm −1 [ 48 ], 1120 cm −1 [ 48 ], and 1270 cm −1 [ 47 ], which were attributed to the lattice oxygen of SnO 2 . The increasing bands at 1302 cm −1 , 1348 cm −1 , 1442 cm −1 , and 1561 cm −1 were attributed to surface carbonates [ 49 ].…”

Section: Resultsmentioning

confidence: 99%

Rhodium Oxide Surface-Loaded Gas Sensors

et al. 2018

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In order to increase their stability and tune-sensing characteristics, metal oxides are often surface-loaded with noble metals. Although a great deal of empirical work shows that surface-loading with noble metals drastically changes sensing characteristics, little information exists on the mechanism. Here, a systematic study of sensors based on rhodium-loaded WO3, SnO2, and In2O3—examined using X-ray diffraction, high-resolution scanning transmission electron microscopy, direct current (DC) resistance measurements, operando diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, and operando X-ray absorption spectroscopy—is presented. Under normal sensing conditions, the rhodium clusters were oxidized. Significant evidence is provided that, in this case, the sensing is dominated by a Fermi-level pinning mechanism, i.e., the reaction with the target gas takes place on the noble-metal cluster, changing its oxidation state. As a result, the heterojunction between the oxidized rhodium clusters and the base metal oxide was altered and a change in the resistance was detected. Through measurements done in low-oxygen background, it was possible to induce a mechanism switch by reducing the clusters to their metallic state. At this point, there was a significant drop in the overall resistance, and the reaction between the target gas and the base material was again visible. For decades, noble metal loading was used to change the characteristics of metal-oxide-based sensors. The study presented here is an attempt to clarify the mechanism responsible for the change. Generalities are shown between the sensing mechanisms of different supporting materials loaded with rhodium, and sample-specific aspects that must be considered are identified.

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Section: Resultsmentioning

confidence: 99%

Rhodium Oxide Surface-Loaded Gas Sensors

et al. 2018

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“…NIR analysis (Figure 1d) contributes to elucidating the mechanism involved during the oxidation process, being directly related to the water molecules adsorbed on the surface of the SnO 2 samples. As seen in Figure 1d there are three characteristic peaks of water, i. e., ∼7,000 cm −1 corresponds to surface hydroxyl groups (1 st overtone), ∼5,000 cm −1 attributed to crystalline water (hydroxide, 1 st overtone) and 4,500 cm −1 attributed to xerogel structure [19] . Normalizing all the peaks by the surface hydroxyl groups, one can see differences in the distribution of crystalline water, which tends to increase (in proportion) according to the annealing temperature.…”

Section: Figurementioning

confidence: 96%

Experimental Evidence of CO₂ Photoreduction Activity of SnO₂ Nanoparticles

Torres

Silva

et al. 2020

ChemPhysChem

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Tin dioxide (SnO2) has intrinsic characteristics that do not favor its photocatalytic activity. However, we evidenced that surface modification can positively influence its performance for CO2 photoreduction in the gas phase. The hydroxylation of the SnO2 surface played a role in the CO2 affinity decreasing its reduction potential. The results showed that a certain selectivity for methane (CH4), carbon monoxide (CO), and ethylene (C2H4) is related to different SnO2 hydrothermal annealing. The best performance was seen for SnO2 annealed at 150 °C, with a production of 20.4 μmol g−1 for CH4 and 16.45 μmol g−1 for CO, while for SnO2 at 200 °C the system produced more C2H4, probably due to a decrease of surface −OH groups.

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“…As has been shown previously, a decrease in reflectance in the visible range of SnO 2 is caused by increased sample absorption originating from the presence of oxygen vacancies, i.e., SnO 2 reduction . [13] In fact, Figure 1 shows that starting from the oxidized gas sensor (air), exposure to increasingly reducing gas environments (air!N 2 !EtOH/air!EtOH/N 2 ) results in a systematic decrease in the reflectance as a result of increasing absorption in the visible, as indicated for example by the behavior at 525 nm (see dashed line). Note that the legend displays the order of the experiments from top to bottom.…”

mentioning

confidence: 99%

Elucidating the Mechanism of Working SnO₂ Gas Sensors Using Combined Operando UV/Vis, Raman, and IR Spectroscopy

Elger

Heß

2019

Angew Chem Int Ed

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SnO 2 is the most widely used metal oxide gas-sensing material but a detailed understanding of its functioning is still lacking despite its relevance for applications. To gain new mechanistic insight into SnO 2 gas sensors under working conditions, we have developed an operando approach based on combined UV/Vis, Raman, and FTIR spectroscopy, allowing us for the first time to relate the sensor response to the concentration of oxygen vacancies in the metal oxide, the nature of the adsorbates, and the gas-phase composition. We demonstrate with the example of ethanol gas sensing that the sensor resistance is directly correlated with the number of surface oxygen vacancies and the presence of surface species, in particular, acetate and hydroxy groups. Our operando results enable an assessment of mechanistic models proposed in the literature to explain gas sensor operation. Owing to their fundamental nature, our findings are of direct relevance also for other metal oxide gas sensors.

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Nanosized tin dioxide: Spectroscopic (UV–VIS, NIR, EPR) and electrical conductivity studies

Cited by 102 publications

References 18 publications

Rhodium Oxide Surface-Loaded Gas Sensors

Rhodium Oxide Surface-Loaded Gas Sensors

Experimental Evidence of CO₂ Photoreduction Activity of SnO₂ Nanoparticles

Elucidating the Mechanism of Working SnO₂ Gas Sensors Using Combined Operando UV/Vis, Raman, and IR Spectroscopy

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Nanosized tin dioxide: Spectroscopic (UV–VIS, NIR, EPR) and electrical conductivity studies

Cited by 102 publications

References 18 publications

Rhodium Oxide Surface-Loaded Gas Sensors

Rhodium Oxide Surface-Loaded Gas Sensors

Experimental Evidence of CO2 Photoreduction Activity of SnO2 Nanoparticles

Elucidating the Mechanism of Working SnO2 Gas Sensors Using Combined Operando UV/Vis, Raman, and IR Spectroscopy

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Product

Resources

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Experimental Evidence of CO₂ Photoreduction Activity of SnO₂ Nanoparticles

Elucidating the Mechanism of Working SnO₂ Gas Sensors Using Combined Operando UV/Vis, Raman, and IR Spectroscopy