Enhanced Reducibility of the Ceria–Tin Oxide Solid Solution Modifies the CO Oxidation Mechanism at the Platinum–Oxide Interface

Study on the Gas-Chromic Character of Pd/TiO2 for Fast Room-Temperature CO Detection

As a widely used support, TiO2 has often been combined with Pd to form highly sensitive gas-chromic materials. Herein, we prepared a series of Pd/TiO2 catalysts with different Pd content (from 0.1 to 5 wt.%) by the impregnation method for their utilization in fast room-temperature CO detection. The detection was simply based on visible color change when the Pd/TiO2 was exposed to CO. The sample with 1 wt.% Pd/TiO2 presented an excellent CO gasochromic character, associated with a maximum chromatic aberration value of 90 before and after CO exposure. Systematic catalyst characterizations of XPS, FT-IR, CO-TPD, and N2 adsorption-desorption and density functional theory calculations for the CO adsorption and charge transfer over the Pd and PdO surfaces were further carried out. It was found that the interaction between CO and the Pd surface was strong, associated with a large adsorption energy of -1.99 eV and charge transfer of 0.196 e. The color change was caused by a reduction in Pd2+ to metallic Pd0 over the Pd/TiO2 surface after CO exposure.

Origin of the Activity Trend in the Oxidative Dehydrogenation of Ethanol over VOx /CeO2

Supported vanadia (VO_x ) is a versatile catalyst for various redox processes where ceria-supported VO_x have shown to be particularly active in the oxidative dehydrogenation (ODH) of alcohols. In this work, we clarify the origin of the volcano-shaped ethanol ODH activity trend for VO_x /CeO_x catalysts using operando quick V K- and Ce L₃ - edge XAS experiments performed under transient conditions. We quantitatively demonstrate that both vanadium and cerium are synergistically involved in alcohol ODH. The concentration of reversible Ce⁴⁺ /Ce³⁺ species was identified as the main descriptor of the alcohol ODH activity. The activity drop in the volcano plot, observed at above ca. 3 V nm^-2 surface loading (ca. 30 % of VO_x monolayer coverage), is related to the formation of spectator V⁴⁺ and Ce³⁺ species, which were identified here for the first time. These results might prove to be helpful for the rational optimization of VO_x /CeO₂ catalysts and the refinement of the theoretical models.

Nanocatalytic Interface to Decode the Phytovolatile Language for Latent Crop Diagnosis in Future Farms

Crop diseases cause the release of volatiles. Here, the use of an SnO₂-based chemoresistive sensor for early diagnosis has been attempted. Ionone is one of the signature volatiles released by the enzymatic and nonenzymatic cleavage of carotene at the latent stage of some biotic stresses. To our knowledge, this is the first attempt at sensing volatiles with multiple oxidation sites, i.e., ionone (4 oxidation sites), from the phytovolatile library, to derive stronger signals at minimum concentrations. Further, the sensitivity was enhanced on an interdigitated electrode by the addition of platinum as the dopant for a favorable space charge layer and for surface island formation for reactive interface sites. The mechanistic influence of oxygen vacancy formation was studied through detailed density functional theory (DFT) calculations and reactive oxygen-assisted enhanced binding through X-ray photoelectron spectroscopy (XPS) analysis.

Effect of oxygen storage materials on the performance of Pt-based three-way catalysts

Pt supported on oxygen storage materials (CeO2 and CeO2–ZrO2) as effective three-way catalysts.

Hydrogenation of pentenal over supported Pt nanoparticles: influence of Lewis-acid sites in the conversion pathway

The superb TOF and high selectivity of Pt/CeAl are associated with the surface properties (e.g. medium Lewis acidic site). The unsaturated Ce4+/Al3+ cations pairs act as the acid sites and electron acceptors to polarize the CO bonds.