Strong Metal-Support Interaction Facilitated Multicomponent Alloy Formation on Metal Oxide Support.

Multicomponent alloy (MA) contains a nearly infinite number of unprecedented active sites through entropy stabilization, which is a desired platform for exploring high-performance catalysts. However, MA catalysts are usually synthesized under severe conditions, which induce support structure collapse and further deteriorate the synergy between MA and support. We propose that a strong metal-support interaction (SMSI) could facilitate the formation of MA by establishing a tunnel of oxygen vacancy for metal atom transport under low reduction temperature (400-600 °C), which exemplifies the holistic design of MA catalysts without deactivating supports. PtPdCoFe MA is readily synthesized on anatase TiO2 with the help of SMSI, which exhibits good catalytic activity and stability for methane combustion. This strategy demonstrates excellent universality on various supports and multicomponent alloy compositions. Our work not only reports a holistic synthesis strategy for MA synthesis by synergizing unique properties of reducible oxides and the mixing entropy of alloy but also offers a new insight that SMSI plays a vigorous role in the formation of alloy NPs on reducible oxides.

Switchable Tuning CO2 Hydrogenation Selectivity by Encapsulation of the Rh Nanoparticles While Exposing Single Atoms.

The switch of CO2 hydrogenation selectivity from CH4 to CO over TiO2 supported Rh catalysts is accomplished via selective encapsulation of Rh nanoparticles while exposing Rh single atoms by high-temperature reduction (HTR) according to their different strong metal-support interaction (SMSI) occurrence conditions, which can be reversed by subsequent oxidation treatment.

Single-Atom Catalysts Based on the Metal-Oxide Interaction.

Metal atoms dispersed on the oxide supports constitute a large category of single-atom catalysts. In this review, oxide supported single-atom catalysts are discussed about their synthetic procedures, characterizations, and reaction mechanism in thermocatalysis, such as water-gas shift reaction, selective oxidation/hydrogenation, and coupling reactions. Some typical oxide materials, including ferric oxide, cerium oxide, titanium dioxide, aluminum oxide, and so on, are intentionally mentioned for the unique roles as supports in anchoring metal atoms and taking part in the catalytic reactions. The interactions between metal atoms and oxide supports are summarized to give a picture on how to stabilize the atomic metal centers, and rationally tune the geometric structures and electronic states of single atoms. Furthermore, several directions in fabricating single-atom catalysts with improved performance are proposed on the basis of state-of-the-art understanding in metal-oxide interactions.

Highly Active and Sintering-Resistant Pt Clusters Supported on FeOx-Hydroxyapatite Achieved by Tailoring Strong Metal-Support Interactions.

The catalytic performance of supported metal catalysts is closely related to their structure. While Pt-based catalysts are widely used in many catalytic reactions because of their exceptional intrinsic activity, they tend to deactivate in high-temperature reactions, requiring a tedious and expensive regeneration process. The strong metal-support interaction (SMSI) is a promising strategy to improve the stability of supported metal nanoparticles, but often at the price of the activity due to either the coverage of the active sites by support overlay and/or the too-strong metal-support bonding. Herein, we newly constructed a supported Pt cluster catalyst by introducing FeOx into hydroxyapatite (HAP) support to fine-tune the SMSIs. The catalyst exhibited not only high catalytic activity but also sintering resistance, without deactivation in a 100 h test for catalytic CO oxidation. Detailed characterizations reveal that FeOx introduced into HAP weaken the strong covalent metal-support interaction (CMSI) between Pt and FeOx while simultaneously inhibiting the oxidative strong metal-support interaction (OMSI) between Pt and HAP, giving rise to both high activity and thermal stability of the supported Pt clusters.

Host-induced alteration of the neighbors of single platinum atoms enables selective and stable hydrogenation of butadiene.

Tuning the coordination neighbors of the metal center is emerging as an elegant approach to manipulating the performance of supported single-atom catalysts in heterogeneous catalysis. Herein, atomically dispersed Pt species with different coordination neighbors hosted on nitrogen-doped carbon (NC) and graphitic carbon nitride (C3N4) are constructed through an impregnation-activation approach. Advanced characterization techniques including X-ray electron microscopy, X-ray absorption spectroscopy, and high angle annular dark-field scanning transmission electron microscopy reveal the different nature of active sites induced by the hosts: i.e., the Pt-Nx configuration in NC but both Pt-N and Pt-O coordinations in C3N4. H2-D2 exchange experiments and electron microscopy further evidence that Pt/NC exhibits a high propensity for H2 splitting and high thermal stability of the Pt species against agglomeration, whereas Pt/C3N4 cannot dissociate H2 and the Pt atoms easily aggregate in the reductive stream. Consequently, when applied in the selective hydrogenation of 1,3-butadiene, Pt/NC exhibits higher selectivity to butenes and excellent stability, but Pt/C3N4 behaves as a nanoparticle analogue favoring deep hydrogenation. The superior selectivity patterns of the single Pt atoms over Pt nanoparticles are rationalized by the inversed adsorption strength between the H2 and 1,3-butadiene molecules at different metal sites, which is substantiated by the kinetic studies.

High-Loading Pt Single-Atom Catalyst on CeO2 -Modified Diatomite Support.

Single-atom catalysis has become a new branch in heterogeneous catalysis. Although the naturally produced SiO2 -based materials are abundant and stable, fabrication of single-atom catalysts on such supports with high loading remains as a formidable challenge due to the lack of bonding sites to anchor the isolated metal species. Herein, modifying the diatomite, a kind of pure SiO2 mineral, with CeO2 nanoparticles is demonstrated to increase the defect sites on the support. The enhanced metal-support interaction maintains the atomic dispersion of Pt species with above 1 wt.% loading, exhibiting good performance in the selective hydrogenation of phenylacetylene to styrene.