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XPS spectra of MoO3 nanorods and CeO2/MoO3 nanorods: a full survey scan spectrum, b Mo 3d spectrum of MoO3, c O 1s spectrum of MoO3, d Ce 3d spectrum of CeO2/MoO3, e Mo 3d spectrum of CeO2/MoO3, f O 1s spectrum of CeO2/MoO3
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The MoO3 nanorods decorated with CeO2 were successfully synthesized by a two-step hydrothermal method, and the microstructure and morphology of CeO2/MoO3 were determined by XRD, XPS, SEM, and TEM. It can be confirmed by SEM that the CeO2 nanoparticles of uniform size were successfully compounded with MoO3 nanorods. According to the gas sensitivity...
Citations
... In addition, the O 1s spectrum of the TiO2/In2O3 and Au/TiO2/In2O3 samples were analyzed as shown in Figure 5e-f. The O1s spectrum was fitted and analyzed by the Gaussian fitting method, and three characteristic peaks were obtained, which corresponded to the lattice oxygen (OL), oxygen vacancies (Ov), and chemisorbed oxygen (OC) [49][50][51], respectively. As shown in Figure 5f, the peaks of OL, OV, and OC were located at about 529.32 eV, 530.10 eV, and 531.63 eV, respectively. ...
Au modified TiO2/In2O3 hollow nanospheres were synthesized by the hydrolysis method using the carbon nanospheres as a sacrificial template. Compared to pure In2O3, pure TiO2, and TiO2/In2O3 based sensors, the Au/TiO2/In2O3 nanosphere-based chemiresistive-type sensor exhibited excellent sensing performances to formaldehyde at room temperature under ultraviolet light (UV-LED) activation. The response of the Au/TiO2/In2O3 nanocomposite-based sensor to 1 ppm formaldehyde was about 5.6, which is higher than that of In2O3 (1.6), TiO2 (2.1), and TiO2/In2O3 (3.8). The response time and recovery time of the Au/TiO2/In2O3 nanocomposite sensor were 18 s and 42 s, respectively. The detectable formaldehyde concentration could go down as low as 60 ppb. In situ diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) was used to analyze the chemical reactions on the surface of the sensor activated by UV light. The improvement in the sensing properties of the Au/TiO2/In2O3 nanocomposites could be attributed to the nanoheterojunctions and electronic/chemical sensitization of the Au nanoparticles.
In order to reduce the impact of greenhouse gases, we have studied a new and efficient photocatalyst to reduce CO2. We recombined the hollow CeO2 with the In2O3 and introduced the oxygen vacancy to obtain the CeO2@In2O3 for the hollow structure of the oxygen vacancy. The test results show that CeO2@In2O3 with oxygen vacancy hollow structure (hereinafter collectively referred to as H-CeO2, H-In2O3, and H-CeO2–x@In2O3–x) have higher photocatalytic reduction activity of CO2 than hollow CeO2 and hollow In2O3. When the illumination time was 4 h, the yields of carbon dioxide reduction to CO and methane were 38.7 and 7.8 μmol·g−1, respectively. Consequently, we explained the photocatalytic reduction mechanism, and carried out the X-ray diffraction (XRD) and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis of H-CeO2, H-In2O3, and H-CeO2–x@In2O3–x. This study summarizes some experience for the study of oxygen vacancy hollow structure photocatalyst, and provides some new ideas in the field of photocatalytic reduction of CO2.Graphical abstract
Hydrogen sulfide (H2S) is a poisonous gas and corrosive with a characteristic rotten egg smell. Exposure to a higher concentration of H2S gas leads to death. Research groups across the globe have been working on developing a gas sensor composed of novel sensing materials to monitor deadly H2S gas for over a decade. Carbon-based materials such as single-wall carbon nanotubes, multi-wall carbon nanotubes, graphene, and graphene derivatives have been incorporated with metal oxides to improve H2S gas sensing properties. Carbon-based composites have unique physicochemical properties which provide the sensor possessing superior sensitivity, selectivity, stability, quick response time, etc. This review highlights the importance of H2S sensors based on rGO/MOx and CNT/MOx, their enhanced sensitivity and selectivity to H2S.
Hollow In2O3@TiO2 double-layer nanospheres were prepared via a facile water bath method using the sacrifice template of carbon nanospheres. It is shown that the size of the In2O3/TiO2 nanocomposites is 150-250 nm, the thickness of the In2O3 shell is about 10 nm, and the thickness of the TiO2 shell is about 15 nm. The sensing performances of the synthesized In2O3/TiO2 nanocomposites-based chemiresistive-type sensor to formaldehyde (HCHO) gas under UV light activation at room temperature have been studied. Compared to the pure In2O3- and pure TiO2-based sensors, the In2O3/TiO2 nanocomposite sensor exhibits much better sensing performances to formaldehyde. The response of the In2O3/TiO2 nanocomposite-based sensor to 1 ppm formaldehyde is about 3.8, and the response time and recovery time are 28 and 50 s, respectively. The detectable formaldehyde concentration can reach as low as 0.06 ppm. The role of the formed In2O3/TiO2 heterojunctions and the involved chemical reactions activated by UV light have been investigated by AC impedance spectroscopy and the in situ diffuse reflectance Fourier transform infrared spectroscopy. The improvement of the sensing properties of In2O3/TiO2 nanocomposites could be attributed to the nanoheterojunctions between the two components and the "combined photocatalytic effects" of UV-light-emitting diode irradiation. Density functional theory calculations demonstrated that introducing heterojunctions could improve the adsorption energy and charge transfer between formaldehyde and sensing materials.
