Morphology and size of Pt on Al2O3: The role of specific metal-support interactions between Pt and Al2O3

Dynamic Behavior of Platinum Atoms and Clusters in the Native Oxide Layer of Aluminum Nanocrystals

Strong metal-support interactions (SMSIs) are well-known in the field of heterogeneous catalysis to induce the encapsulation of platinum (Pt) group metals by oxide supports through high temperature H2 reduction. However, demonstrations of SMSI overlayers have largely been limited to reducible oxides, such as TiO2 and Nb2O5. Here, we show that the amorphous native surface oxide of plasmonic aluminum nanocrystals (AlNCs) exhibits SMSI-induced encapsulation of Pt following reduction in H2 in a Pt structure dependent manner. Reductive treatment in H2 at 300 °C induces the formation of an AlOx SMSI overlayer on Pt clusters, leaving Pt single-atom sites (Ptiso) exposed available for catalysis. The remaining exposed Ptiso species possess a more uniform local coordination environment than has been observed on other forms of Al2O3, suggesting that the AlOx native oxide of AlNCs presents well-defined anchoring sites for individual Pt atoms. This observation extends our understanding of SMSIs by providing evidence that H2-induced encapsulation can occur for a wider variety of materials and should stimulate expanded studies of this effect to include nonreducible oxides with oxygen defects and the presence of disorder. It also suggests that the single-atom sites created in this manner, when combined with the plasmonic properties of the Al nanocrystal core, may allow for site-specific single-atom plasmonic photocatalysis, providing dynamic control over the light-driven reactivity in these systems.

Fine-Tuning of Pt Dispersion on Al2O3 and Understanding the Nature of Active Pt Sites for Efficient CO and NH3 Oxidation Reactions

Fine-tuning the dispersion of active metal species on widely used supports is a research hotspot in the catalysis community, which is vital for achieving a balance between the atomic utilization efficiency and the intrinsic activity of active sites. In this work, using bayerite Al(OH)3 as support directly or after precalcination at 200 or 550 °C, Pt/Al2O3 catalysts with distinct Pt dispersions from single atoms to clusters (ca. 2 nm) were prepared and evaluated for CO and NH3 removal. Richer surface hydroxyl groups on AlOx(OH)y support were proved to better facilitate the dispersion of Pt. However, Pt/Al2O3 with relatively lower Pt dispersion could exhibit better activity in CO/NH3 oxidation reactions. Further reaction mechanism study revealed that the Pt sites on Pt/Al2O3 with lower Pt dispersion could be activated to Pt0 species much easier under the CO oxidation condition, on which a higher CO adsorption capacity and more efficient O2 activation were achieved simultaneously. Compared to Pt single atoms, PtOx clusters could also better activate NH3 into -NH2 and -HNO species. The higher CO adsorption capacity and the more efficient NH3/O2 activation ability on Pt/Al2O3 with relatively lower Pt dispersion well explained its higher CO/NH3 oxidation activity. This study emphasizes the importance of avoiding a singular pursuit of single-atom catalyst synthesis and instead focusing on achieving the most effective Pt species on Al2O3 support for targeted reactions. This approach avoids unnecessary limitations and enables a more practical and efficient strategy for Pt catalyst fabrication in emission control applications.

Enhancing Benzene Combustion Activity through Preferential Platinum Atom Exposure via Strategic Pt-Cu Alloying

Volatile organic compounds such as benzene are hazardous air pollutants that require effective elimination. Noble metal-based catalysts exhibit high benzene combustion activity, but their prohibitive cost necessitates strategies to enhance utilization efficiency. This study investigates a Pt-Cu alloy catalyst for improved benzene combustion by preferentially exposing Pt active sites through Cu alloying. Aberration-corrected scanning transmission electron microscopy and X-ray spectroscopy characterize the nanoscale distribution and enrichment of Pt on the alloy surface. Kinetic measurements demonstrate substantially enhanced activity compared with Pt catalysts, attributed to increased Pt metallic site exposure rather than alteration of the reaction mechanism. In situ Fourier transform infrared (FTIR) spectroscopy reveals a higher abundance of terrace-like Pt sites in the alloy, beneficial for benzene adsorption. Partial pressure dependence analyses indicate competitive adsorption of benzene and O2, following Langmuir-Hinshelwood kinetics. These findings provide conceptual insights into tuning surface composition in bimetallic catalysts to optimize noble metal efficiency, with broad applicability for sustainable catalytic process advancement.

Regulating Pt-based noble metal catalysts for the catalytic oxidation of volatile organic compounds: a mini review

Volatile organic compounds (VOCs) are an important class of environmental pollutants, and there is much interest in China to eliminate such pollutants. Noble metal catalysts have long been a family of catalysts with high efficiency and good low-temperature catalytic activity. As a representative of the noble metals, Pt has been widely used. This paper reviews the research trend of Pt-based catalysts for the catalytic oxidation of VOCs, and it compares several important components of Pt-based catalysts. The size of Pt particles, supported carriers, and reaction mechanism are reviewed. Toluene in VOCs is the main research subject. The activity, stability, water resistance, and selectivity of a series of Pt-based catalysts are summarized.

Direct synthesis of triazines from alcohols and amidines using supported Pt nanoparticle catalysts via the acceptorless dehydrogenative methodology

We report a cost-effective, green, and acceptorless dehydrogenative one-pot synthesis of triazines from primary alcohols and amidines using an alumina-supported Pt nanoparticle catalyst (Pt/Al2O3).

Atomic Structure of Pd-, Pt-, and PdPt-Based Catalysts of Total Oxidation of Methane: In Situ EXAFS Study

In this study, 3%Pd/Al2O3, 3%Pt/Al2O3 and bimetallic (1%Pd + 2%Pt)/Al2O3 catalysts were examined in the total oxidation of methane in a temperature range of 150–400 °C. The evolution of the active component under the reaction conditions was studied by transmission electron microscopy and in situ extended X-ray absorption fine structure (EXAFS) spectroscopy. It was found that the platinum and bimetallic palladium-platinum catalysts are more stable against sintering than the palladium catalysts. For all the catalysts, the active component forms a “core-shell” structure in which the metallic core is covered by an oxide shell. The “core-shell” structure for the platinum and bimetallic palladium-platinum catalysts is stable in the temperature range of 150–400 °C. However, in the case of the palladium catalysts the metallic core undergoes the reversible oxidation at temperatures above 300 °C and reduced to the metallic state with the decrease in the reaction temperature. The scheme of the active component evolution during the oxidation of methane is proposed and discussed.

Strong response of Pt clusters to the environment and conditions, formation of metastable states, and simple methods to trace the reversible changes

Subnanometric metal particles, the so-called "clusters", are known to be responsive to their surroundings, but the detection of occurring changes, understanding the causes, and predicting the consequences are still extremely difficult for such small particles. Our study was aimed at estimating the potential of adsorption-based methods for these purposes. Using carbon monoxide as a probing molecule, which readily adsorbs on both bare and H-covered Pt surface, we have probed the adsorption properties of highly dispersed Pt/γ-Al₂O₃ samples after treatments under different atmospheres and temperatures (H₂ or inert gas, 25-500 °C). The combined results of CO-chemisorption measurements, CO TPD, CO TPO, H₂-by-CO displacement, and H₂ TPD suggest that the system shuttles between two states: one with oxygen vacancies in the support and the other one with redox-active oxygen near the Pt clusters. These extreme states can be reversibly created and deleted, giving rise to innumerable intermediate structures that differ in the amount, binding strength, and/or reactivity of adsorbed species. Two adsorbates could act cooperatively, resulting in hydrogen spillover onto the support and making the adsorbate-metal-support interactions even more complex. Implications for better understanding the dynamic behavior of oxide-supported clusters and nanoparticles are discussed.

Influence of Different Thermal Aging Conditions on Soot Combustion with Catalyst by Thermogravimetric Analysis

Diesel particulates are deposited in the diesel particulate filter and removed by the regeneration process. The Printex-U (PU) particles are simulated as the diesel soot to investigate the influence of thermal aging conditions on soot combustion performance with the addition of catalysts. The comprehensive combustion index S, combustion stability index Rw and peak temperature Tp are obtained to evaluate the combustion performance. Compared with the PU/Pt mixtures of different Pt contents (2 g/ft3, 3.5 g/ft3, and 5 g/ft3), the 10 g/ft3 Pt contents improve soot combustion with the outstanding oxygen absorption ability. When the weight ratio of PU/Pt mixture is 1:1, the promoted effect achieves the maximum degree. The S and Rw increase to 8.90 × 10-8 %2min-2°C-3 and 39.11 × 105, respectively, compared with pure PU. After the thermal aging process, the PU/Pt mixture with a 350 °C aging temperature for 10 h promotes the soot combustion the best when compared to pure PU particles. It is not good as the PU/Pt mixture without aging, because the inner properties of soot and Pt/Al2O3 catalyst may have been changed. The S and Rw are 9.07 × 10-8 %2min-2°C-3 and 38.39 × 105, respectively, which are close to the no aging mixture. This work plays a crucial role in understanding the mechanism of the comprehensive effect of soot and catalyst on soot combustion after the thermal aging process.

Efficient catalytic combustion of toluene at low temperature by tailoring surficial Pt0 and interfacial Pt-Al(OH)x species

Exploring highly efficient and low-cost supported Pt catalysts is attractive for the application of volatile organic compounds (VOCs) combustion. Herein, efficient catalytic combustion of toluene at low temperature over Pt/γ-Al₂O₃ catalysts has been demonstrated by tailoring active Pt species spatially. Pt/γ-Al₂O₃ catalyst with low Pt-content (0.26 wt%) containing both interfacial Pt-Al(OH)_x and surficial metallic Pt (Pt⁰) species exhibited super activity and water-resistant stability for toluene oxidation. The strong metal-support interaction located at the Al-OH-Pt interfaces elongated the Pt-O bond and contributed to the oxidation of toluene. Meanwhile, the OH group at the Al-OH-Pt interfaces had the strongest adsorption and activation capability for toluene and the derived intermediate species were subsequently oxidized by oxygen species activated by surficial Pt⁰ to yield carbon dioxide and water. This work initiated an inspiring sight to the design of active Pt species for the VOCs combustion.

Vapor-Phase Furfural Decarbonylation over a High-Performance Catalyst of 1%Pt/SBA-15

A high-performance Pt catalyst supported on SBA-15 was developed for furfural decarbonylation. Compared to Pt catalysts loaded on microporous DeAl-Hbeta zeolite and hierarchical micro-mesoporous MFI nanosheet (NS) materials, the 1%Pt/SBA-15 catalyst afforded notably higher activity, furan selectivity and stability owing to the negligible acid sites and proper mesopores on the SBA-15 support. Among a set of 1%Pt/SBA-15 catalysts bearing Pt nanoparticles (NPs) with sizes of 2.4–4.3 nm, the catalyst with 3.7 nm Pt NPs afforded the highest furan selectivity. Over the optimal catalyst, 88.6% furan selectivity and ca. 90% furfural conversion were obtained at 573 K and a high weight hourly space velocity (WHSV) of 16.5 h−1. Moreover, the reaction temperatures at 440–573 K and the ratios of H2 to furfural at 0.79–9.44 did not affect the reaction selectivity notably, showing that the reaction over 1%Pt/SBA-15 can be conducted over a wide range of conditions. The catalyst was stable under the harsh reaction conditions and lasted for 90 h without significant deactivation, demonstrating the superior property of SBA-15 as a catalyst support for furfural decarbonylation.