A Sacrificial Coating Strategy Toward Enhancement of Metal–Support Interaction for Ultrastable Au Nanocatalysts

Enrooted-Type Metal-Support Interaction Boosting Oxygen Evolution Reaction in Acidic Media

Supported metal catalysts with appropriate metal-support interactions (MSIs) hold a great promise for heterogeneous catalysis. However, ensuring tight immobilization of metal clusters/nanoparticles on the support while maximizing the exposure of surface active sites remains a huge challenge. Herein, we report an Ir/WO3 catalyst with a new enrooted-type MSI in which Ir clusters are, unprecedentedly, atomically enrooted into the WO3 lattice. The enrooted Ir atoms decrease the electron density of the constructed interface compared to the adhered (root-free) type, thereby achieving appropriate adsorption toward oxygen intermediates, ultimately leading to high activity and stability for oxygen evolution in acidic media. Importantly, this work provides a new enrooted-type supported metal catalyst, which endows suitable MSI and maximizes the exposure of surface active sites in contrast to the conventional adhered, embedded, and encapsulated types.

In Situ Reconstruction of Active Heterointerface for Hydrocarbon Combustion through Thermal Aging over Strontium-Modified Co3O4 Nanocatalyst with Good Sintering Resistance

The issue of catalyst deactivation due to sintering has gained significant attention alongside the rapid advancement of thermal catalysts. In this work, a simple Sr modification strategy was applied to achieve highly active Co3O4-based nanocatalyst for catalytic combustion of hydrocarbons with excellent antisintering feature. With the Co1Sr0.3 catalyst achieving a 90% propane conversion temperature (T90) of only 289 °C at a w8 hly space velocity of 60,000 mL·g-1·h-1, 24 °C lower than that of pure Co3O4. Moreover, the sintering resistance of Co3O4 catalysts was greatly improved by SrCO3 modification, and the T90 over Co1Sr0.3 just increased from 289 to 337 °C after thermal aging at 750 °C for 100 h, while that over pure Co3O4 catalysts increased from 313 to 412 °C. Through strontium modification, a certain amount of SrCO3 was introduced on the Co3O4 catalyst, which can serve as a physical barrier during the thermal aging process and further formation of Sr-Co perovskite nanocrystals, thus preventing the aggregation growth of Co3O4 nanocrystals and generating new active SrCoO2.52-Co3O4 heterointerface. In addition, propane durability tests of the Co1Sr0.3 catalysts showed strong water vapor resistance and stability, as well as excellent low-temperature activity and resistance to sintering in the oxidation reactions of other typical hydrocarbons such as toluene and propylene. This study provides a general strategy for achieving thermal catalysts by perfectly combining both highly low-temperature activity and sintering resistance, which will have great significance in practical applications for replacing precious materials with comparative features.

Cell-inspired design of cascade catalysis system by 3D spatially separated active sites

Cells possess isolated compartments that spatially confine different enzymes, enabling high-efficiency enzymatic cascade reactions. Herein, we report a cell-inspired design of biomimetic cascade catalysis system by immobilizing Fe single atoms and Au nanoparticles on the inner and outer layers of three-dimensional nanocapsules, respectively. The different metal sites catalyze independently and work synergistically to enable engineered and cascade glucose detection. The biomimetic catalysis system demonstrates ~ 9.8- and 2-fold cascade activity enhancement than conventional mixing and coplanar construction systems, respectively. Furthermore, the biomimetic catalysis system is successfully demonstrated for the colorimetric glucose detection with high catalytic activity and selectivity. Also, the proposed gel-based sensor is integrated with smartphone to enable real-time and visual determination of glucose. More importantly, the gel-based sensor exhibits a high correlation with a commercial glucometer in real samples detection. These findings provide a strategy to design an efficient biomimetic catalysis system for applications in bioassays and nanobiomedicines.

Site-Selective Superassembly of a Multilevel Asymmetric Nanomotor with Wavelength-Modulated Propulsion Mechanisms

Micro-/nanomotors with advanced motion manipulation have recently received mounting interest; however, research focusing on the motion regulation strategies is still limited, as the simple construction and composition of micro-/nanomotors restrict the functionality. Herein, a multifunctional TiO₂-SiO₂-mesoporous carbon nanomotor is synthesized via an interfacial superassembly strategy. This nanomotor shows an asymmetric matchstick-like structure, with a head composed of TiO₂ and a tail composed of SiO₂. Mesoporous carbon is selectively grown on the surface of TiO₂ through surface-charge-mediated assembly. The spatially anisotropic distribution of the photocatalytic TiO₂ domain and photothermal carbon domain enables multichannel control of the motion, where the speed can be regulated by energy input and the directionality can be regulated by wavelength. Upon UV irradiation, the nanomotor exhibits a head-leading self-diffusiophoretic motion, while upon NIR irradiation, the nanomotor exhibits a tail-leading self-thermophoretic motion. As a proof-of-concept, this mechanism-switchable nanomotor is employed in wavelength-regulated targeted cargo delivery on a microfluidic chip. From an applied point of view, this nanomotor holds potential in biomedical applications such as active drug delivery and phototherapy. From a fundamental point of view, this research can provide insight into the relationship between the nanostructures, propulsion mechanisms, and motion performance.

Review on supported metal catalysts with partial/porous overlayers for stabilization

Heterogeneous catalysts of supported metals are important for both liquid-phase and gas-phase chemical transformations which underpin the petrochemical sector and manufacture of bulk or fine chemicals and pharmaceuticals. Conventional supported metal catalysts (SMC) suffer from deactivation resulting from sintering, leaching, coking and so on. Besides the choice of active species (e.g. atoms, clusters, nanoparticles) to maximize catalytic performances, strategies to stabilize active species are imperative for rational design of catalysts, particularly for those catalysts that work under heated and corrosive reaction conditions. The complete encapsulation of metal active species within a matrix (e.g. zeolites, MOFs, carbon, etc.) or core-shell arrangements is popular. However, the use of partial/porous overlayers (PO) to preserve metals, which simultaneously ensures the accessibility of active sites through controlling the size/shape of diffusing reactants and products, has not been systematically reviewed. The present review identifies the key design principles for fabricating supported metal catalysts with partial/porous overlayers (SMCPO) and demonstrates their advantages versus conventional supported metals in catalytic reactions.

Nonclassical Strong Metal-Support Interactions for Enhanced Catalysis

Strong metal-support interaction (SMSI), which encompasses reversible encapsulation and de-encapsulation and modulation of surface adsorption properties, imposes great impacts on the performance of heterogeneous catalysts. Recent development of SMSI has surpassed the prototypical encapsulated Pt-TiO₂ catalyst, affording a series of conceptually novel and practically advantageous catalytic systems. Here we provide our perspective on recent progress in nonclassical SMSIs for enhanced catalysis. Unravelling the structural complexity of SMSI necessitates the combination of multiple characterization techniques at different scales. Synthesis strategies leveraging chemical, photonic, and mechanochemical driving forces further expand the definition and application scope of SMSI. Exquisite structure engineering permits elucidation of the interface, entropy, and size effect on the geometric and electronic characteristics. Materials innovation places the atomically thin two-dimensional materials at the forefront of interfacial active site control. A broader space is awaiting exploration, where exploitation of metal-support interactions brings compelling catalytic activity, selectivity, and stability.

Controlling the Size of Au Nanoparticles on Reducible Oxides with the Electrochemical Potential

Controlling the size of Au nanoparticles (NPs) and their interaction with the oxide support is important for their catalytic performance in chemical reactions, such as CO oxidation and water-gas shift. It is known that the oxygen vacancies at the surface of support oxides form strong chemical bonding with the Au NPs and inhibit their coarsening and deactivation. The resulting Au/oxygen vacancy interface also acts as an active site for oxidation reactions. Hence, small Au NPs are needed to increase the density of the Au/oxide interface. A dynamic way to control the size of the Au NPs on an oxide support is desirable but has been missing in the field. Here, we demonstrate an electrochemical method to control the size of the Au NPs by controlling the surface oxygen vacancy concentration of the support oxide. Oxides with different reducibilities, La_0.8Ca_0.2MnO_3±δ and Pr_0.1Ce_0.9O_2-δ, are used as model support oxides. By applying the electrochemical potential, we achieve a wide range of effective oxygen pressures, pO₂ (10^-37-10¹⁴ atm), in the support oxides. Applying the cathodic potential creates a high concentration of oxygen vacancies and forms finely distributed Au NPs with sizes of 7-13 nm at 700-770 °C in 10 min, while the anodic potential oxidizes the surface and increases the size of the Au NPs. The onset cathodic potential required to create small Au NPs depends strongly on the reducibility of the support oxide. The Au NPs did not undergo sintering even at 700-770 °C under the cathodic potential and also were stable in catalytically relevant conditions without potential.

Hierarchical hollow zeolite fiber in catalytic applications: A critical review

Zeolites have widely been studied because of the better performance as catalysts and supports. However, the zeolites with only micropores have drawbacks in reactivity and selectivity due to limitation of diffusivity. The hollow zeolite fibers (HZF) with hierarchical porosity however can overcome the problem. The HZF can be synthesized by such methods as incorporated substrate removal method, solid-solid transformation method, co-axial electrospinning technology, dry-wet spinning technology, and hollow fiber incorporation method. The unique hierarchical porous structure leads to the great improvement in the diffusion efficiency of reactants. The catalytic zeolite membrane fibers are the most commonly used as they have stronger catalyst stability and higher catalytic selectivity. The HZFs are suitable in catalytic applications such as selective catalysis, CO preferential oxidation, air purification and wastewater treatment. In order that the HZFs can be applied to industrial operations, more research work should be carried out, such as developments of self-assembly pure HZFs, catalytic substrate incorporated HZFs, HZFs with gradient multicomponent zeolites and HZFs with nanoscale diameters.

Surface deposition of 2D covalent organic frameworks for minimizing nanocatalyst sintering during hydrogenation

A strategy of in situ depositing 2D COFs on heterogeneous catalysts was reported for the first time to suppress the agglomeration and sintering of the supported metal nanoparticles during hydrogenation processes. The COF-decorated nanocatalysts exhibited excellent stability in various hydrogenation reactions including the reduction of dimethyl oxalate (DMO), furfural, and other chemicals.

The preparation of ultrastable Al3+ doped CeO2 supported Au catalysts: Strong metal-support interaction for superior catalytic activity towards CO oxidation

The classical strong metal-support interaction (SMSI) plays a key role in improving thermal stability for supported Au catalysts. However, it always decreases the catalytic activity because of the encapsulation of Au species by support. Herein, we demonstrate that Al³⁺ is a functional additive which could effectively improve both catalytic activity and sintering resistant property for H₂ pretreated Al³⁺ doped CeO₂ supported Au (AuCeAl) catalyst at high temperature. The physical characterization and in-situ DRIFTS results provide insight that more oxygen vacancies generated by Al³⁺ doping could be as preferential adsorption sites for CO molecules when the encapsulation of Au species occurred, which is certificated by an accelerated formation of bicarbonate species. In the meantime, smaller Au nanoparticles with higher dispersion (2.8 nm, 85.63%) is achieved in AuCeAl catalysts, compared with that in CeO₂ supported Au (AuCe) catalysts (5.1 nm, 36.17%). Additionally, the as-prepared AuCeAl catalysts also have superior catalytic performance even after calcination at 800 °C in air.

The Effect of a Hydrogen Reduction Procedure on the Microbial Synthesis of a Nano-Pd Electrocatalyst for an Oxygen-Reduction Reaction

Noble-metal electrocatalysts supported by biological-organism-derived carbons have attracted attention from the public due to the growing demands for green synthesis and environmental protection. Carbonization at high temperatures and hydrogen reduction are critical steps in this technical route. Herein, Shewanella oneidensis MR-1 were used as precursors, and the effects of the hydrogen-reduction procedure on catalysts were explored. The results showed that the performances of FHTG (carbonization followed by hydrogen reduction) displayed the best performance. Its ECSA (electrochemical surface area), MA (mass activity), and SA (specific activity) reached 35.01 m2 g−1, 58.39 A·g−1, and 1.66 A cm−2, respectively, which were 1.17, 1.75, and 1.50 times that of PHTG (prepared through hydrogen reduction followed by carbonization) and 1.56, 2.26, and 1.44 times that of DHTG (double hydrogen reduction). The high performance could be attributed to its fine particle size and rich N content, and the specific regulation mechanism was also proposed in this paper. This study opens a practical guide for effectively avoiding particle agglomeration during the fabrication process for catalysts.

Atomically Dispersed Pt on Three-Dimensional Ordered Macroporous SnO2 for Highly Sensitive and Highly Selective Detection of Triethylamine at a Low Working Temperature

Triethylamine (TEA) is a widely used volatile organic chemical, which is harmful and can cause headache, dizziness, and respiratory discomfort. Developing an efficient sensor to detect trace amounts of TEA is significant for industrial and healthcare monitoring. In this work, SnO₂ with a three-dimensional ordered macroporous structure (3DOM) was prepared through a polymethylmethacrylate sphere template route. The TEA sensing performance of the 3DOM SnO₂ was enhanced through Pt loading. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy images and X-ray absorption fine-structure analysis indicate that Pt on the 3DOM 0.20% Pt/SnO₂ surface mainly exists in the state of atomic dispersion, which results in more active sites, higher Hall mobility and active oxygen contents, and lower response energy barriers. The 0.20% Pt/SnO₂ sensor has a low operating temperature of 80 °C and a low limit of detection (0.32 ppb). Because of the uniform adsorption of TEA on the atomically dispersed Pt, the 3DOM Pt/SnO₂ sensor exhibits high selectivity.

Harnessing Strong Metal-Support Interaction to Proliferate the Dry Reforming of Methane Performance by In Situ Reduction

The strong bonding at the interface between the metal and the support, which can inhibit the undesirable aggregation of metal nanoparticles and carbon deposition from reforming of hydrocarbon, is well known as the classical strong metal-support interaction (SMSI). SMSI of nanocatalysts was significantly affected by heat treatment and reducing conditions during catalyst preparation.the heat treatment and reduction conditions during catalyst preparation. SMSI can be weakened by the decrement of metal-doped sites in the supporting oxide and can often deactivate catalysts by the encapsulation of active sites through these processes. To retain SMSI near the active sites and to enhance the catalytic activity of the nanocatalyst, it is essential to increase the number of surficial metal-doped sites between nanometal and the support. Herein, we propose a mild reduction process using dry methane (CH₄/CO₂) gas that suppresses the aggregation of nanoparticles and increases the exposed interface between the metal and support, Ni and cerium oxide. The effects of mild reduction on the chemical state of Ni-cerium oxide nanocatalysts were specifically investigated in this study. As a result, mild reduction led to form large amounts of the Ni³⁺ phase at the catalyst surface of which SMSI was significantly enhanced. It can be easily fabricated while the dry reforming of methane (DRM) reaction is on stream. The superior performance of the catalyst achieved a considerably high CH₄ conversion rate of approximately 60% and stable operation up to 550 h at a low temperature, 600 °C.

Manipulating Copper Dispersion on Ceria for Enhanced Catalysis: A Nanocrystal-Based Atom-Trapping Strategy

Due to tunable redox properties and cost-effectiveness, copper-ceria (Cu-CeO2 ) materials have been investigated for a wide scope of catalytic reactions. However, accurately identifying and rationally tuning the local structures in Cu-CeO2 have remained challenging, especially for nanomaterials with inherent structural complexities involving surfaces, interfaces, and defects. Here, a nanocrystal-based atom-trapping strategy to access atomically precise Cu-CeO2 nanostructures for enhanced catalysis is reported. Driven by the interfacial interactions between the presynthesized Cu and CeO2 nanocrystals, Cu atoms migrate and redisperse onto the CeO2 surface via a solid-solid route. This interfacial restructuring behavior facilitates tuning of the copper dispersion and the associated creation of surface oxygen defects on CeO2 , which gives rise to enhanced activities and stabilities catalyzing water-gas shift reaction. Combining soft and solid-state chemistry of colloidal nanocrystals provide a well-defined platform to understand, elucidate, and harness metal-support interactions. The dynamic behavior of the supported metal species can be further exploited to realize exquisite control and rational design of multicomponent nanocatalysts.

Tunable metal-support interaction of Pt/CeO2 catalyst via surfactant-assisted strategy: Insight into the total oxidation of CO and toluene

Catalytic oxidation is promising in removing atmospheric pollutants to address serious environmental concerns. Supported Pt-based catalysts (e.g., Pt/CeO₂) are most effective for catalytic removal of atmospheric pollutants. However, the catalytic performance is largely affected by the oxidation state of Pt, oxygen vacancy and metal-support interaction (MSI). Herein, two different types of Pt/CeO₂ catalyst were fabricated via surfactant-assisted strategy and treated in different annealing atmospheres, which was applied to carbon monoxide (CO) and toluene (C₇H₈) oxidation, respectively. The results reveal that the as-synthesized Pt/CeO₂-NH catalyst is favorable to C₇H₈ oxidation, whereas the contrast Pt/CeO₂-AH is favorable to CO oxidation. Meanwhile, Pt/CeO₂-NH catalyst also has high thermal stability facing high temperature (e.g., 400 °C). Various characterizations, such as in-situ Raman, XPS, CO-DRIFTS and XANES, clarifies that the Pt/CeO₂-NH catalyst has a higher surface Pt⁰ proportion, a weak MSI and more oxygen vacancies. The corresponding theoretical calculation also supports the experimental results. These results advance efficient regulation and fundamental understanding of MSI, and the design of heterogeneous catalysts.

Highly efficient catalytic reduction of 4-nitrophenol and organic dyes by ultrafine palladium nanoparticles anchored on CeO2 nanorods

Uniformly dispersed Pd nanoparticles on certain supports exhibit exceptional catalytic performance toward various environmental applications. In this work, ultrafine Pd nanoparticles anchored on CeO₂ nanorods were synthesized via an absorption-in situ reduction method. The activity of the CeO₂/Pd nanocomposites was systematically investigated toward reduction of 4-nitrophenol (4-NP) and organic dyes including methyl blue, rhodamine B, methyl orange, and Congo red. The results indicated that the CeO₂/Pd nanocomposites with different weight ratios of Pd nanoparticles (10.23 wt%, 11.01 wt%, and 14.27 wt%) can almost completely reduce 4-NP with a rate constant of 3.31×10^-1, 3.22×10^-1, and 2.23×10^-1 min^-1. Besides, the 10.23 wt% CeO₂/Pd nanocomposites exhibit remarkable enhanced catalytic activity toward reduction of organic dyes. The catalysts display ideal stability after being used for three times for the reduction of 4-NP. We believe that our strategy demonstrated here offers insights into the design and fabrication of novel Pd-based nanocomposites for various heterogeneous catalysis applications.

Highly Active CuO/KCC−1 Catalysts for Low-Temperature CO Oxidation

Copper catalysts have been extensively studied for CO oxidation at low temperatures. Previous findings on the stability of such catalysts, on the other hand, revealed that they deactivated badly under extreme circumstances. Therefore, in this work, a series of KCC−1-supported copper oxide catalysts were successfully prepared by impregnation method, of which 5% CuO/KCC−1 exhibited the best activity: CO could be completely converted at 120 °C. The 5% CuO/KCC−1 catalyst exhibited better thermal stability, which is mainly attributed to the large specific surface area of KCC−1 that facilitates the high dispersion of CuO species, and because the dendritic layered walls can lengthen the movement distances from particle-to-particle, thus helping to slow down the tendency of active components to sinter. In addition, the 5% CuO/KCC−1 has abundant mesoporous and surface active oxygen species, which are beneficial to the mass transfer and promote the adsorption of CO and the decomposition of Cu+–CO species, thus improving the CO oxidation performance of the catalyst.

Facilitating Catalytic Purification of Auto-Exhaust Carbon Particles via the Fe2O3{113} Facet-dependent Effect in Pt/Fe2O3 Catalysts

The purification efficiency of auto-exhaust carbon particles in the catalytic aftertreatment system of vehicle exhaust is strongly dependent on the interface nanostructure between the noble metal component and oxide supports. Herein, we have elaborately synthesized the catalysts (Pt/Fe₂O₃-R) of Pt nanoparticles decorated on the hexagonal bipyramid α-Fe₂O₃ nanocrystals with co-exposed twelve {113} and six {104} facets. The area ratios (R) of co-exposed {113} to {104} facets in α-Fe₂O₃ nanocrystals were adjusted by the fluoride ion concentration in the hydrothermal method. The strong Pt-Fe₂O₃{113} facet interaction boosts the formation of coordination unsaturated ferric sites for enhancing adsorption/activation of O₂ and NO. Pt/Fe₂O₃-R catalysts exhibited the Fe₂O₃{113} facet-dependent performance during catalytic purification of soot particles in the presence of H₂O. Among the catalysts, the Pt/Fe₂O₃-19 catalyst exhibits the highest catalytic activities (T₅₀ = 365 °C, TOF = 0.13 h^-1), the lowest apparent activation energy (69 kJ mol^-1), and excellent catalytic stability during soot purification. Combined with the results of characterizations and density functional theory calculations, the catalytic mechanism is proposed: the active sites located at the Pt-Fe₂O₃{113} interface can boost the key step of NO oxidation to NO₂. The crystal facet engineering is an effective strategy to obtain efficient catalysts for soot purification in practical applications.

Catalyst overcoating engineering towards high-performance electrocatalysis

Clean and sustainable energy needs the development of advanced heterogeneous catalysts as they are of vital importance for electrochemical transformation reactions in renewable energy conversion and storage devices. Advances in nanoscience and material chemistry have afforded great opportunities for the design and optimization of nanostructured electrocatalysts with high efficiency and practical durability. In this review article, we specifically emphasize the synthetic methodologies for the versatile surface overcoating engineering reported to date for optimal electrocatalysts. We discuss the recent progress in the development of surface overcoating-derived electrocatalysts potentially applied in polymer electrolyte fuel cells and water electrolyzers by correlating catalyst intrinsic structures with electrocatalytic properties. Finally, we present the opportunities and perspectives of surface overcoating engineering for the design of advanced (electro)catalysts and their deep exploitation in a broad scope of applications.

Hexagonal Boron Nitride Meeting Metal: A New Opportunity and Territory in Heterogeneous Catalysis

Two dimensional (2D) hexagonal boron nitride (h-BN) has been ignored for a long time in catalysis research because of its chemical inertness. Recently there has been a significant advance highlighting the role of metal/h-BN interfaces in catalytic applications. In this Perspective, we summarize state-of-the-art progress regarding h-BN-involved metal catalysts. Vacancy- and defect-rich h-BN sheets are able to anchor and modify supported metals, in which the interfacial metal-support interaction effect helps to enhance catalytic performance. Oxidative etching of h-BN sheets causes encapsulation of metal catalysts via boron oxide (BO_x) species, which work synergistically with neighboring metal sites in catalysis. Covering a metal surface with ultrathin h-BN shells creates a 2D nanoreactor featuring confinement effect, providing a novel way to modulate metal-catalyzed reactions. Given all those fascinating combinations of metal catalyst and h-BN, the emerging opportunity when h-BN meets metal in heterogeneous catalysis is clearly underlined. The outlook, especially the challenges in the field, are discussed as well.

Significant Improvement of Catalytic Performance for Chlorinated Volatile Organic Compound Oxidation over RuOx Supported on Acid-Etched Co3O4

Ru catalysts have attracted increasing attention in catalytic oxidation of chlorinated volatile organic compounds (CVOCs). However, the development of Ru catalysts with high activity and thermal stability for CVOC oxidation still poses significant challenges due to their restrictive relationship. Herein, a strategy for constructing surface defects on Co₃O₄ support by acid etching was utilized to strengthen the interaction between active RuO_x species and the Co₃O₄ support. Consequently, both the dispersity and thermal stability of RuO_x species were significantly improved, achieving both high activity and stability of Ru catalysts for CVOC oxidation. The optimized Ru catalyst on the HF-etched Co₃O₄ support (Ru/Co₃O₄-F) achieved complete oxidation of vinyl chloride at 260 °C under 30 000 mL·g^-1·h^-1, which was lower than 300 °C for the Ru catalyst on the original Co₃O₄ (Ru/Co₃O₄). More importantly, the Ru species on the Ru/Co₃O₄-F catalyst were hardly lost after calcination at 500-700 °C and even reacting at 650 °C for 120 h. On this basis, the polychlorinated byproducts over the Ru/Co₃O₄-F catalyst were almost completely effaced by phosphate modification on the catalyst surface. These findings show that the method combining acid etching of the support and phosphate modification provides a strategy for the advancement of catalyst design for CVOC oxidation.

Photoinduced Strong Metal-Support Interaction for Enhanced Catalysis

Strong metal-support interaction (SMSI) construction is a pivotal strategy to afford thermally robust nanocatalysts in industrial catalysis, but thermally induced reactions (>300 °C) in specific gaseous atmospheres are generally required in traditional procedures. In this work, a photochemistry-driven methodology was demonstrated for SMSI construction under ambient conditions. Encapsulation of Pd nanoparticles with a TiO_x overlayer, the presence of Ti³⁺ species, and suppression of CO adsorption were achieved upon UV irradiation. The key lies in the generation of separated photoinduced reductive electrons (e^-) and oxidative holes (h⁺), which subsequently trigger the formation of Ti³⁺ species/oxygen vacancies (O_v) and then interfacial Pd-O_v-Ti³⁺ sites, affording a Pd/TiO₂ SMSI with enhanced catalytic hydrogenation efficiency. The as-constructed SMSI layer was reversible, and the photodriven procedure could be extended to Pd/ZnO and Pt/TiO₂.

The fabrication of hollow ZrO2 nanoreactors encapsulating Au-Fe2O3 dumbbell nanoparticles for CO oxidation

Nanosized Au catalysts suffer from serious sintering problems during synthesis or catalytic reactions at high temperatures. In this work, we integrate dumbbell-shaped Au-Fe₃O₄ heterostructures into hollow ZrO₂ nanocages to make Au-Fe₂O₃@ZrO₂ yolk-shell nanoreactors with high activity as well as ultra-high sintering resistance for high-temperature CO oxidation. The synthesis starts with the fabrication of a (Au-Fe₃O₄)@SiO₂@ZrO₂ core-shell nanostructure with a Au-Fe₃O₄ dumbbell nanoparticle (DB) core and SiO₂/ZrO₂ double shells, followed by calcination and the selective removal of the inner SiO₂ shell with alkaline solution to obtain Au-Fe₂O₃@ZrO₂ nanoreactors. The retained ZrO₂ hollow (outer) shells protect the Au NPs from aggregation at temperatures up to 900 °C and show excellent long-term stability. Compared to Au@ZrO₂ yolk-shell nanoreactors, Au-Fe₂O₃@ZrO₂ shows improved activity in CO oxidation due to the active Au-Fe₂O₃ interface. This strategy can be extended to other yolk-shell nanoreactors with various nanocomposites and for different catalytic reactions.

Enhanced strong metal–support interactions between Pt and WO3–x nanowires for the selective hydrogenation of p-chloronitrobenzene

Pt/WO3–x nanocatalysts demonstrate significantly enhanced catalytic performance due to the strong interaction between Pt and WO3–x nanowires.

Sinter-resistant platinum nanocatalysts immobilized by biochar for alkane hydroisomerization

The supported platinum nanocatalysts synthesized by the first proposed biochar-assisted strategy exhibited excellent catalytic performance and metal stability in n-alkane hydroisomerization.

Photocatalytic hydroxylation of benzene to phenol over organosilane-functionalized FeVO4 nanorods

Surface silylation of FeVO4 with organosilane functional groups is a promising strategy to realize kinetic control of photocatalytic benzene hydroxylation reactions.

Boosting the sintering resistance of platinum–alumina catalyst via a morphology-confined phosphate-doping strategy

The size-dependent metal–support interaction, high surface area, and, above all, the support morphology-confined effect contribute to a good sintering-resistant catalyst.

Catalytic Performance of Lanthanum Promoted Ni/ZrO2 for Carbon Dioxide Reforming of Methane

Nickel catalysts supported on zirconium oxide and modified by various amounts of lanthanum with 10, 15, and 20 wt.% were synthesized for CO2 reforming of methane. The effect of La2O3 as a promoter on the stability of the catalyst, the amount of carbon formed, and the ratio of H2 to CO were investigated. In this study, we observed that promoting the catalyst with La2O3 enhanced catalyst activities. The conversions of the feed, i.e., methane and carbon dioxide, were in the order 10La2O3 > 15La2O3 > 20La2O3 > 0La2O3, with the highest conversions being about 60% and 70% for both CH4 and CO2 respectively. Brunauer–Emmett–Teller (BET) analysis showed that the surface area of the catalysts decreased slightly with increasing La2O3 doping. We observed that 10% La2O3 doping had the highest specific surface area (21.6 m2/g) and the least for the un-promoted sample. The higher surface areas of the promoted samples relative to the reference catalyst is an indication of the concentration of the metals at the mouths of the pores of the support. XRD analysis identified the different phases available, which ranged from NiO species to the monoclinic and tetragonal phases of ZrO2. Temperature programmed reduction (TPR) analysis showed that the addition of La2O3 lowered the activation temperature needed for the promoted catalysts. The structural changes in the morphology of the fresh catalyst were revealed by microscopic analysis. The elemental compositions of the catalyst, synthesized through energy dispersive X-ray analysis, were virtually the same as the calculated amount used for the synthesis. The thermogravimetric analysis (TGA) of spent catalysts showed that the La2O3 loading of 10 wt.% contributed to the gasification of carbon deposits and hence gave about 1% weight-loss after a reaction time of 7.5 h at 700 °C.

Catalytic performance promoted on Pt-based diesel oxidation catalyst assisted by polyvinyl alcohol

Eliminating vehicle emission is of importance due to the severe limit value. The work reports a convenient strategy of improving dispersion of platinum-based catalyst with the assistance of polyvinyl alcohol in a varied addition amount. Following the "two-step" annealing techniques, the catalytic performance of the polymer-assisted catalysts in diesel was obviously enhanced because of the improved dispersion of the platinum. Based on experimental results, the long chains of polymer resulting in the steric effect are presumed to isolate platinum ion, inhibiting the aggregation of platinum particles and then improving its dispersion. And the hydroxyl bonding between the polymers could convey electron to platinum species, leading to the lower platinum valence state. Both effects are positive resulting in an excellent NO maximum conversion of around 65% at the optimal introduction of 5 mass% of polymer, as the diesel oxidation catalyst (DOC), which could be inclined to a good purification in the diesel aftertreatment. Hopefully, the convenient research method could initiate the exploration and application of polymer-assisted catalysts for well-dispersed noble metal nanoparticles in eliminating exhaust emission.

Electronic Oxide-Metal Strong Interaction (EOMSI)

Strong metal-support interaction of supported metal catalysts is an important concept to describe the effect of metal-support interactions on the structures and catalytic performances of supported metal particles. By using an example of CeO_x adlayers supported on Ag nanocrystals, herein a concept of electronic oxide-metal strong interaction (EOMSI) is put forward; this interaction significantly affects the electronic structures of oxide adlayers through metal-to-oxide charge transfer. The EOMSI can stabilize oxide adlayers in a low oxidation state under ambient conditions, which individually are not stable; moreover, the oxide adlayers experiencing the EOMSI are resistant to high-temperature oxidation in air to a certain extent. Such an EOMSI concept helps to generalize the strong influence of oxide-metal interactions on the structures and catalytic performance of oxide/metal inverse catalysts, which have been attracting increasing attention.

Real-time atomistic simulation of the Ostwald ripening of TiO2 supported Au nanoparticles

Ostwald ripening (OR), one of the major processes of nanoparticle sintering, is critical for the rational design of functional nanomaterials. However, the atomistic mechanism of OR has not been fully understood, because the characterization of interparticle transport of atoms in real-time is challenging by either experiments or theoretical simulations. Thus, current understandings are based on ad hoc assumptions about the OR mechanism, which have never been confirmed yet at the atomic scale. Herein, we realized all-atom kinetic Monte Carlo simulation of sintering of TiO2 supported Au nanoparticles (NPs) through the OR mechanism at millisecond timescales. We demonstrated that the "semi-spherical" assumption should be removed. The OR process was a stagewise process determined by different rate-determining steps, which is in contrast to the single-stage presumption. Au dimers, rather than monomers as generally assumed, were exchanged among different NPs. Besides, we proposed a new kinetic model for describing the determining rate of OR without presumptions. This work brings deeper insights into the atomistic OR mechanism and also paves the way for real-time monitoring of catalyst sintering at the atomic scale.

Sinter-Resistant Nanoparticle Catalysts Achieved by 2D Boron Nitride-Based Strong Metal-Support Interactions: A New Twist on an Old Story

Strong metal-support interaction (SMSI) is recognized as a pivotal strategy in hetereogeneous catalysis to prevent the sintering of metal nanoparticles (NPs), but issues including restriction of supports to reducible metal oxides, nonporous architecture, sintering by thermal treatment at >800 °C, and unstable nature limit their practical application. Herein, the construction of non-oxide-derived SMSI nanocatalysts based on highly crystalline and nanoporous hexagonal boron nitride (h-BN) 2D materials was demonstrated via in situ encapsulation and reduction using NaBH₄, NaNH₂, and noble metal salts as precursors. The as-prepared nanocatalysts exhibited robust thermal stability and sintering resistance to withstand thermal treatment at up to 950 °C, rendering them with high catalytic efficiency and durability in CO oxidation even in the presence of H₂O and hydrocarbon simulated to realistic exhaust systems. More importantly, our generic strategy offers a novel and efficient avenue to design ultrastable hetereogeneous catalysts with diverse metal and support compositions and architectures.

Atomically Dispersed Au on In2O3 Nanosheets for Highly Sensitive and Selective Detection of Formaldehyde

As an important industrial chemical, formaldehyde is used in various fields but is harmful to health. Developing a convenient detection device for formaldehyde is significant. Based on atomically dispersed Au on In₂O₃ nanosheets, a formaldehyde sensor was fabricated in this work. The highly dispersed Au obtained by the ultraviolet (UV) light-assisted reduction method helps improve the sensing performance. A meager loading amount (0.01 wt %) of Au on In₂O₃ nanosheets exhibits high sensitivity toward ppb-level formaldehyde. Au acts as an electron sink and promotes the oxidation of formaldehyde. Atomically dispersed Au on In₂O₃ nanosheets decreases the activation energy and increases the number of active sites, which result in a highly efficient conversion of formaldehyde and a marked resistance change of the fabricated sensors. The selective adsorption and oxidation of formaldehyde on single atom Au's uniform sites establish excellent selectivity. Besides, the sensor exhibits short response/recovery time and excellent stability, with promising applications in formaldehyde detection.

Size-Dependent Pt-TiO2 Strong Metal-Support Interaction

The strong metal-support interaction (SMSI) is one of the most important concepts in heterogeneous catalysis. Herein we report a study of Pt-TiO₂ SMSI using Pt/rutile TiO₂(110) model catalysts with different Pt particle sizes by means of X-ray photoelectron spectroscopy, ion scattering spectroscopy, and the adsorption of probe molecules. The acquired results unambiguously demonstrate a size dependence of the Pt-TiO₂ SMSI, in which SMSI occurs barely between supported Pt clusters and the TiO₂(110) substrate but obviously between supported Pt nanoparticles and the TiO₂(110) substrate. Such a size-dependent SMSI could be associated with size-dependent electronic structures of the supported Pt particles. These results highlight the sensitivity of the SMSI to the size of supported metal particles, which greatly advances the fundamental understanding.