Thermodynamically and Kinetically Stabilized Pt Clusters Against Sintering on CeO2 Nanofibers Through Enclosing CeO2 Nanocubes

Ultrafine PtGa Clusters Confined in Porous ZrOx/SiO2 Nanofibers for Enhanced Propane Dehydrogenation

Ultrafine Pt clusters exhibit superior activity for propane dehydrogenation compared to larger Pt nanoparticles; however, they are prone to sintering at high operating temperatures, leading to a decline in both activity and selectivity. In this work, porous ZrOx/SiO2 nanofibers featuring highly dispersed ZrOx nanodomains within a SiO2 matrix were successfully fabricated via a high-throughput blow-spinning process. The abundant and thermal-stable 1.6 nm micropores significantly stabilize 1.5 nm PtGa clusters against sintering at temperatures over 800 °C, due to the pore confinement. Moreover, the electron transfer from Ga to Pt is significantly enhanced in close proximity to ZrOx, contributing to metallic Pt with exceptional activity toward C-H bond activation. Thereby, the sinter-resistant PtGa/ZrOx/SiO2 nanofibers maintained 98.8% propylene selectivity and 43.2% propane conversion rate over 100 h of reaction, with a deactivation rate constant down to 0.0045 h-1. This work explores a sinter-resistant catalytic system based on oxide nanofibers and elaborates a new logic for the design of high-performance propane dehydrogenation catalysts with long-term stability.

A self-regenerating Pt/Ge-MFI zeolite for propane dehydrogenation with high endurance

Supported noble metal cluster catalysts are typically operated under severe conditions involving switching between reducing and oxidizing atmospheres, causing irreversible transformation of the catalyst structure and thereby leading to permanent deactivation. We discovered that various platinum (Pt) precursors spontaneously disperse in a germanium-MFI (Ge-MFI) zeolite, which opposes the Ostwald ripening phenomenon, producing self-regenerating Pt/Ge-MFI catalysts for propane dehydrogenation. These catalysts reversibly switch between Pt clusters and Pt single atoms in response to reducing reaction and oxidizing regeneration conditions. This environmental adaptability allows them to completely self-regenerate over 110 reaction and regeneration cycles in propane dehydrogenation, and they exhibited unprecedented sintering resistance when exposed to air at 800°C for 10 days. Such spontaneous metal dispersion in a Ge-MFI zeolite is a robust and versatile methodology for fabricating various rhodium, ruthenium, iridium, and palladium cluster catalysts.

Photothermal-Propelled Au-CeO2 Micromotors for Synergistic Photocatalytic-Photothermal Antibacterial Systems

Facing the great challenge for efficient utilization of solar light, the design of photothermal-propelled micromotors is significant for converting optical energy into thermal energy to achieve the in situ manipulated motion. Assisted by the photothermal-propelled function, a synergistic photocatalytic-photothermal antibacterial system is successfully constructed in this work, based on the Au-CeO2 micromotor. The selective growth of CeO2 nanoparticles on the surface of Au nanorods (NRs) is achieved with the adjustable Au exposure ratio. The strong interaction of CeO2 with Au NRs realizes the enhanced visible light harvesting and the promoted photo-induced charge separation. Especially, the self-induced thermophoretic force on asymmetric lollipop-like L-Au-CeO2 with higher Au exposure ratio is more powerful than that on symmetric core-shelled CS-Au-CeO2 and dumbbell-like D-Au-CeO2. As a result, its local temperature gradient is greater and thus realizes the in situ manipulated motion with higher velocity and stronger directionality. It further facilitates the contact with bacteria and promotes the synergistic photocatalytic-photothermal antibacterial performance for the probe bacteria of Escherichia coli. This powerful photothermal-propelled Au-CeO2 micromotor shows significant potential for the microorganism control in biomedical and environmental applications.

Sinter- and Water-Resistant Pt Enabled by High Entropy of Porous Oxide Nanofibers

Supported ultrafine noble metal species, especially for Pt, suffer from inevitable sintering at temperatures as low as 80 °C, severely limiting their stability and thus their practical applications. In this work, a strategy is demonstrated using the high-entropy effect to prevent sub-2.6 nm Pt nanoparticles from sintering. Due to the higher mixing entropy and thus lower Gibbs free energy of porous high-entropy oxide (HEO) nanofibers in the catalytic system, the supported Pt remained thermally stable up to 1000 °C, as verified by in situ HAADF-STEM observation. Even after being hydrothermally aged with 10 vol% vapor at 850 °C, this catalytic system maintained the Pt size of 2.9 nm, demonstrating remarkable sinter-resistance and water tolerance. Particularly, after aging at 850 °C, the Pt/HEO catalytic system maintained its full CO conversion for 338 h without any decline. These results highlight the positive effect of increasing configurational entropy on the thermal stability of the entire catalytic system, providing a reliable solution for catalytic conversions involving high temperatures.

Wireless Thermochromic Platform Based on Au/SiO2 Photonic Crystals for Operando Monitoring of Catalyst Sintering with Machine Learning

Operando monitoring of the catalyst sinter-degree during reactions is essential for achieving a stable, safe, and efficient chemical engineering process. This work introduces a wireless thermochromic platform that utilizes machine learning to correlate color changes with the sinter-degree of catalysts and to identify hot spots during chemical reactions. After being decorated with sub-2 nm Au clusters, SiO2 photonic crystals were endowed with a distinct color change from the inherent blue hue of SiO2 photonic crystals to the distinctive red shade associated with Au clusters, due to the gradual growth of Au clusters over a wide temperature range from 25 to 900 °C. With the assistance of an artificial neural network, a robust correlation was established between the observed color change and the sinter-degree of Au species. After training, the smart Au/SiO2 catalyst achieved self-visualization for the sinter-degree of Au species within 12.4 μm × 12.4 μm, during CO oxidation. Moreover, an intelligent noninvasive platform can be constructed by patterning Au/SiO2 photonic crystals into quick response codes, for real-time monitoring of temperature distribution at a micro-region scale (208 μm × 208 μm) within 5 ms during chemical reactions. The Au/SiO2 thermochromic platform enables wireless data transmission and facilitates the programmable warning of abnormal hot spots in reactors. This work serves as a technical reserve for future research on the development of advanced catalysts and offers further insight into the chemical engineering process.

Synergistic effect of scattered rare metals on Pt/CeO2 for propane oxidative dehydrogenation with CO2

The oxidative dehydrogenation of propane with CO2 (CO2-ODP) is a green industrial process for producing propene. Cerium oxide-supported platinum-based (Pt/CeO2) catalysts exhibit remarkable reactivity toward propane and CO2 due to the unique delicate balance of C-H and C[double bond, length as m-dash]O bond activation. However, the simultaneous activation and cleavage of C-H, C-C, and C-O bonds on Pt/CeO2-based catalysts may substantially impede the selective activation of C-H bonds during the CO2-ODP process. Here, we report that the scattered rare metal oxide (SRO x , SR = Ga, In) overlayer on Pt/CeO2 exhibits extraordinary activity and selectivity for the CO2-ODP reaction. With the assistance of Pt, the SRO x -Pt/CeO2 could achieve a propane conversion of 38.13% and a CO2 conversion of 67.72%. More importantly, the selectivity of the product propene has increased from 33.28% to 88.24%, a level that is even comparable to the outstanding performance of currently reported PtSn/CeO2 catalysts. A mechanistic study reveals that the strong affinity of the overlayer SRO x to the propane reduces the barrier of C-H bond activation and balances the C-H cleavage rates and the C-O bond groups, accounting for the excellent selective CO2-ODP performance of SRO x -Pt/CeO2 catalysts. The SRO x -modified Pt/CeO2 strategy offers a novel approach to modulating CO2-ODP, thereby facilitating the highly selective preparation of propene.

Engineering Asymmetric Strain within C-Shaped CeO2 Nanofibers for Stabilizing Sub-3 nm Pt Clusters against Sintering

Ultrafine noble metals have emerged as advanced nanocatalysts in modern society but still suffer from unavoidable sintering at temperatures above 250 °C (e.g., Pt). In this work, closely packed CeO2 grains were confined elegantly in fibrous nanostructures and served as a porous support for stabilizing sub-3 nm Pt clusters. Through precisely manipulating the asymmetry of obtained nanofibers, uneven strain was induced within C-shaped CeO2 nanofibers with tensile strain at the outer side and compressive strain at the inner side. As a result, the enriched oxygen vacancies significantly improved adhesion of Pt to CeO2, thereby boosting the sinter-resistance of ultraclose sub-3 nm Pt clusters. Notably, no aggregation was observed even after exposure to humid air at 750 °C for 12 h, which is far beyond their Tammann temperature (sintering onset temperature, below 250 °C). In situ HAADF-STEM observation revealed a unique sintering mechanism, wherein Pt clusters initially migrate toward the grain boundaries with concentrated stain and undergo slight coalescence, followed by subsequent Ostwald ripening at higher temperatures. Moreover, the sinter-resistant Pt/C-shaped CeO2 effectively catalyzed soot combustion (over 700 °C) in a durable manner. This work provides a new insight for developing sinter-resistant catalysts from the perspective of strain engineering within nano-oxides.

Enhancement of Mineralization Ability and Water Resistance of Vanadium-Based Catalysts for Catalytic Oxidation of Chlorobenzene by Platinum Loading

The design of a catalyst with multifunctional sites is one of the effective methods for low-temperature catalytic oxidation of chlorinated volatile organic compounds (CVOCs). The loss of redox sites and competitive adsorption of H2O prevalent in the treatment of industrial exhaust gases are the main reasons for the weak mineralization ability and poor water vapor resistance of V-based catalysts. In this work, platinum (Pt) is selected to combine with the V/CeO2 catalyst, which provides more redox sites and H2O dissociative activation sites and further enhances its catalytic performance. The results show that PtV/CeO2 achieves 90% of the CO2 yield at 318 °C and maintains excellent catalytic activity rather than continuous deactivation within 15 h after water vapor injection. The formation of Pt-O-V bonds enhances the redox ability and promotes deep oxidation of polychlorinated intermediates, accounting for the significantly improved mineralization ability of PtV/CeO2. The dissociative activation effect of Pt on H2O molecules strengthens the migration and activation of V-adsorbed H2O, precluding V-poisoning and notably improving water resistance. This study lays a solid foundation for the efficient degradation of chlorobenzene under humid conditions.

Constructing Heterointerfaces in Dual-Phase High-Entropy Oxides to Boost O2 Activation and SO2 Resistance for Mercury Removal in Flue Gas

The low O2 activation ability at low temperatures and SO2 poisoning are challenges for metal oxide catalysts in the application of Hg0 removal in flue gas. A novel high-entropy fluorite oxide (MgAlMnCo)CeO2 (Co-HEO) with the second phase of spinel is synthesized by the microwave hydrothermal method for the first time. A high efficiency of Hg0 removal (close to 100%) is achieved by Co-HEO catalytic oxidation at temperatures as low as 100 °C and in the atmosphere of 145 μg m-3 Hg0 at a high GHSV (gas hourly space velocity) of 95,000 h-1. According to O2-TPD and in situ FT-IR, this extremely superior catalytic oxidation performance at low temperatures originates from the activation ability of Co-HEO to transform O2 into superoxide and peroxide, which is promoted by point defects induced from the spinel/fluorite heterointerfaces. Meanwhile, SO2 resistance of Co-HEO for Hg0 removal is also improved up to 2000 ppm due to the high-entropy-stabilized structure, construction of heterointerfaces, and synergistic effect of the multicomponents for inhibiting the oxidation of SO2 to surface sulfate. The design strategy of the dual-phase high-entropy material launches a new route for metal oxides in the application of catalytic oxidation and SO2 resistance.