Renaissance of Strong Metal-Support Interactions.

Strong metal-support interactions (SMSIs) have emerged as a significant and cutting-edge area of research in heterogeneous catalysis. They play crucial roles in modifying the chemisorption properties, interfacial structure, and electronic characteristics of supported metals, thereby exerting a profound influence on the catalytic properties. This Perspective aims to provide a comprehensive summary of the latest advancements and insights into SMSIs, with a focus on state-of-the-art in situ/operando characterization techniques. This overview also identifies innovative designs and applications of new types of SMSI systems in catalytic chemistry and highlights their pivotal role in enhancing catalytic performance, selectivity, and stability in specific cases. Particularly notable is the discovery of SMSI between active metals and metal carbides, which opens up a new era in the field of SMSI. Additionally, the strong interactions between atomically dispersed metals and supports are discussed, with an emphasis on the electronic effects of the support. The chemical nature of SMSI and its underlying catalytic mechanisms are also elaborated upon. It is evident that SMSI modification has become a powerful tool for enhancing catalytic performance in various catalytic applications.

Size-dependent strong metal-support interaction in TiO2 supported Au nanocatalysts.

The strong metal-support interaction (SMSI) has long been studied in heterogonous catalysis on account of its importance in stabilizing active metals and tuning catalytic performance. As a dynamic process taking place at the metal-support interface, the SMSI is closely related to the metal surface properties which are usually affected by the size of metal nanoparticles (NPs). In this work we report the discovery of a size effect on classical SMSI in Au/TiO2 catalyst where larger Au particles are more prone to be encapsulated than smaller ones. A thermodynamic equilibrium model was established to describe this phenomenon. According to this finding, the catalytic performance of Au/TiO2 catalyst with uneven size distribution can be improved by selectively encapsulating the large Au NPs in a hydrogenation reaction. This work not only brings in-depth understanding of the SMSI phenomenon and its formation mechanism, but also provides an alternative approach to refine catalyst performance.

Hypertension/prehypertension and its determinants in pediatric IgA nephropathy.

Immunoglobulin A nephropathy (IgAN) is a major cause of secondary hypertension (HT) of renal origin - a significant prognostic factor of IgAN. In children, similar to HT, prehypertension (pre-HT) is becoming a significant health issue. However, the role of secondary HT and pre-HT (HT/pre-HT) in the progression of pediatric IgAN remains unclear. We investigated the effects of HT/pre-HT on prognosis and its determinants as well as their correlation with clinicopathological parameters to identify more effective therapeutic targets.This single-center retrospective study compared clinicopathological features and treatment outcomes between patients with and without HT/pre-HT in 108 children with IgAN. Independent risk factors for HT/pre-HT were evaluated; segmental glomerulosclerosis was a significant variable, whose relationship with clinicopathological parameters was analyzed.Clinical outcomes of patients with and without HT/pre-HT differed considerably (P = .006) on ≥6 months follow-up. Patients with HT/pre-HT reached complete remission less frequently than those without HT/pre-HT (P = .014). Age, serum creatinine, prothrombin time, and segmental glomerulosclerosis or adhesion were independent risk factors for HT/pre-HT in pediatric IgAN (P = .012, P = .017, P = .002, and P = .016, respectively). Segmental glomerulosclerosis or adhesion was most closely associated with glomerular crescents (r = 0.456, P < .01), followed by Lees grades (r = 0.454, P < .01), renal arteriolar wall thickening (r = 0.337, P < .01), and endocapillary hypercellularity (r = 0.306, P = .001). The intensity of IgA deposits, an important marker of pathogenetic activity in IgAN, was significantly associated with the intensity and location of fibrinogen deposits (intensity: r = 0.291, P = .002; location: r = 0.275, P = .004).HT/pre-HT in pediatric IgAN patients is an important modifiable factor. A relationship is observed between HT/pre-HT and its determinants, especially segmental glomerulosclerosis. Potential therapeutic approaches for IgAN with HT/pre-HT might be directed toward the management of coagulation status, active lesions, and hemodynamics for slowing disease progression.

Remarkable active-site dependent H2O promoting effect in CO oxidation.

The interfacial sites of supported metal catalysts are often critical in determining their performance. Single-atom catalysts (SACs), with every atom contacted to the support, can maximize the number of interfacial sites. However, it is still an open question whether the single-atom sites possess similar catalytic properties to those of the interfacial sites of nanocatalysts. Herein, we report an active-site dependent catalytic performance on supported gold single atoms and nanoparticles (NPs), where CO oxidation on the single-atom sites is dramatically promoted by the presence of H2O whereas on NPs' interfacial sites the promoting effect is much weaker. The remarkable H2O promoting effect makes the Au SAC two orders of magnitude more active than the commercial three-way catalyst. Theoretical studies reveal that the dramatic promoting effect of water on SACs originates from their unique local atomic structure and electronic properties that facilitate an efficient reaction channel of CO + OH.

Oxidative strong metal-support interactions (OMSI) of supported platinum-group metal catalysts.

Supported platinum-group metal (PGM) catalysts are widely used in many important industrial processes. Metal-support interaction is of great importance in tailoring their catalytic performance. Here, we report the first example of oxidative strong metal-support interactions (OMSIs) between PGM and hydroxyapatite (HAP) which can be extended to PGM and ZnO. It occurred under high-temperature oxidation conditions accompanied by the encapsulation of PGM by HAP and electron transfer between PGM and HAP. With this OMSI, the aggregation and leaching of PGMs were significantly inhibited, resulting in an excellent catalytic stability and much improved reusability of supported Pt and Pd catalysts, respectively. This is the first time to find that PGMs can manifest OMSI which benefits the stabilization of PGM catalysts under oxidative reaction conditions. This new type of SMSI not only contributed to a deeper understanding of SMSI but also provided a new way to develop new stable PGM catalysts.

Classical strong metal-support interactions between gold nanoparticles and titanium dioxide.

Supported metal catalysts play a central role in the modern chemical industry but often exhibit poor on-stream stability. The strong metal-support interaction (SMSI) offers a route to control the structural properties of supported metals and, hence, their reactivity and stability. Conventional wisdom holds that supported Au cannot manifest a classical SMSI, which is characterized by reversible metal encapsulation by the support upon high-temperature redox treatments. We demonstrate a classical SMSI for Au/TiO2, evidenced by suppression of CO adsorption, electron transfer from TiO2 to Au nanoparticles, and gold encapsulation by a TiO x overlayer following high-temperature reduction (reversed by subsequent oxidation), akin to that observed for titania-supported platinum group metals. In the SMSI state, Au/TiO2 exhibits markedly improved stability toward CO oxidation. The SMSI extends to Au supported over other reducible oxides (Fe3O4 and CeO2) and other group IB metals (Cu and Ag) over titania. This discovery highlights the general nature of the classical SMSI and unlocks the development of thermochemically stable IB metal catalysts.

Ultrastable Hydroxyapatite/Titanium-Dioxide-Supported Gold Nanocatalyst with Strong Metal-Support Interaction for Carbon Monoxide Oxidation.

Supported Au nanocatalysts have attracted intensive interest because of their unique catalytic properties. Their poor thermal stability, however, presents a major barrier to the practical applications. Here we report an ultrastable Au nanocatalyst by localizing the Au nanoparticles (NPs) in the interfacial regions between the TiO2 and hydroxyapatite. This unique configuration makes the Au NP surface partially encapsulated due to the strong metal-support interaction and partially exposed and accessible by the reaction molecules. The strong interaction helps stabilizing the Au NPs while the partially exposed Au NP surface provides the active sites for reactions. Such a catalyst not only demonstrated excellent sintering resistance with high activity after calcination at 800 °C but also showed excellent durability that outperforms a commercial three-way catalyst in a simulated practical testing, suggesting great potential for practical applications.

Strong Metal-Support Interactions between Gold Nanoparticles and Nonoxides.

The strong metal-support interaction (SMSI) is of great importance for supported catalysts in heterogeneous catalysis. We report the first example of SMSI between Au nanoparticles (NPs) and hydroxyapatite (HAP), a nonoxide. The reversible encapsulation of Au NPs by HAP support, electron transfer, and changes in CO adsorption are identical to the classic SMSI except that the SMSI of Au/HAP occurred under oxidative condition; the opposite condition for the classical SMSI. The SMSI of Au/HAP not only enhanced the sintering resistance of Au NPs upon calcination but also improved their selectivity and reusability in liquid-phase reaction. It was found that the SMSI between Au and HAP is general and could be extended to other phosphate-supported Au systems such as Au/LaPO4. This new discovery may open a new way to design and develop highly stable supported Au catalysts with controllable activity and selectivity.