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The mass specific rates and propylene selectivity of ZnO catalysts exhibit a volcano relation with the size of ZnO in the propane dehydrogenation (PDH) reaction.

Enhanced water resistance of the K2GeF6:Mn4+ phosphor by a dense Al2O3 passivation layer via ALD.

Controlling the chemical environments of the active metal atom including both coordination number (CN) and local composition (LC) is vital to achieve active and stable single-atom catalysts (SACs), but remains challenging. Here we synthesized a series of supported Pt1 SACs by depositing Pt atoms onto the pretuned anchoring sites on nitrogen-doped carbon using atomic layer deposition. In hydrogenation of para-chloronitrobenzene, the Pt1 SAC with a higher CN about four but less pyridinic nitrogen (Npyri) content exhibits a remarkably high activity along with superior recyclability compared to those with lower CNs and more Npyri. Theoretical calculations reveal that the four-coordinated Pt1 atoms with about 1 eV lower formation energy are more resistant to agglomerations than the three-coordinated ones. Composition-wise decrease of the Pt-Npyri bond upshifts gradually the Pt-5d center, and minimal one Pt-Npyri bond features a high-lying Pt-5d state that largely facilitates H2 dissociation, boosting hydrogenation activity remarkably.

Particle size governs the geometric and electronic structure of metal nanoparticles (NPs), shaping their catalytic performance. However, size-dependent entanglement in the geometric and electronic structures often leads to a trade-off between activity and selectivity, limiting the optimization of the overall catalytic performance. Here we show that precisely controlled deposition of a platinum monolayer on large gold NPs breaks the activity–selectivity trade-off on particle size in platinum-catalysed chemoselective hydrogenation of halonitrobenzenes, resulting in a remarkable activity, along with a 99% selectivity for haloanilines under mild conditions. The high activity results from upshift of the platinum 5d-band centre through platinum lattice expansion and ligand effect, whereas the high selectivity is caused by exposing more terrace sites on large particles. The geometric and electronic properties of bimetallic monolayer materials, distinct from monometallic NPs and alloys, constitute a promising platform for the rational design of metal catalysts with superior performance in hydrogenation reactions. Chemoselective reactions are often characterized by an activity–selectivity trade-off that renders their optimization difficult. Here gold nanoparticles equipped with a platinum monolayer are introduced that, thanks to lattice expansion and ligand effect, achieve a remarkable performance for the chemoselective hydrogenation of halonitrobenzenes

Sustainable methanol production via CO2 hydrogenation leads to increased interest in the understanding of active phase of Cu/ZnO/Al2O3 (CZA) catalyst. Model catalysts of ZnO/Cu(111) with structures varied from two-dimensional planar to three-dimensional nanoparticles were prepared by atomic layer deposition (ALD) method. By combing scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) at near-ambient pressure of CO2 hydrogenation, we reveal that the submonolayer ZnO/Cu(111) transformed into Cu-Zn alloy under 10 mbar CO2/H2 at 493 K, and underwent a partial re-oxidation during evacuation. The dynamic phase transformation of ZnO/Cu(111) may partly explain the existence of differences and apparently contradictory theories to account for the origin of active phase in CZA catalysts.

Regulation of the atom-atom interspaces of dual-atom catalysts is essential to optimize the dual-atom synergy to achieve high activity but remains challenging. Herein, we report an effective strategy to regulate the Pt

For supported metal catalysts, the underlying support not only disperses and stabilizes metal particles, but also modulates their electronic structures remarkably, and even directly participates in catalytic reactions. Here we report that Pd nanoparticles (NPs) supported on oxygen-functionalized carbon black (Pd/O-C) show an unexpected inverse trend of selectivity on Pd particle size in chemoselective hydrogenation of para-chloronitrobenzene (p-CNB), compared to those on carbon black (Pd/C). In situ X-ray photoemission spectroscopy reveals that the Pd NPs are more positively charged with decrease of particle size in both samples, while the Pd NPs in Pd/O-C have relatively higher fractions of positive Pdδ+ species than those in Pd/C with similar sizes. Fourier transform infrared spectroscopy shows that the balance of positive Pdδ+ species strongly modulates the competitive adsorption of -NO2 and -Cl group in p-CNB according to their different electronegativities. As a consequence, we, for the first time, demonstrate that a moderate positive charge of Pd NPs is essential to improve the p-chloroaniline (p-CAN) selectivity, while too high or too low positive charge could impel the adsorption of the less negatively charged -Cl group, thus generating the dehalogenated aniline by-product. These findings suggest that precise tailoring of the electronic structures of metal NPs could be essential for design of high chemoselective metal catalysts.

Semi-hydrogenation of acetylene to ethylene is an important process to purify ethylene streams in industry. However, among current approaches reported in the literature, high ethylene selectivity has been generally achieved at the expense of activity. Herein, we show that a Ga2 O3 coating of Ag@Pd core-shell bimetallic nanoparticle catalysts, allows improvement of the ethylene selectivity to a much greater extent than the coating of monometallic Pd nanoparticles, while preserving a remarkable intrinsic activity, approximately 50 times higher than the benchmark catalyst of Pd1 Ag single-atom alloys (SAAs). Importantly, the resulting catalyst also shows excellent long-term stability, by suppressing coke formation efficiently. Spectroscopic characterization reveals that weakened ethylene adsorption by bimetallic electronic synergy, and oxide site isolation are both essential for the high ethylene selectivity and high-coking resistance. H-D exchange measurements further show that the Ga2 O3 -coated Ag@Pd catalyst possesses a much higher activity of H2 activation than that of Pd1 Ag SAAs, thus boosting the hydrogenation activity at the same time.

Supported metal nanoclusters consisting of several dozen atoms are highly attractive for heterogeneous catalysis with unique catalytic properties. However, the metal nanocluster catalysts face the challenges of thermal sintering and consequent deactivation owing to the loss of metal surface areas particularly in the applications of high-temperature reactions. Here, we report that sulfur—a documented poison reagent for metal catalysts—when doped in a carbon matrix can stabilize ~1 nanometer metal nanoclusters (Pt, Ru, Rh, Os, and Ir) at high temperatures up to 700 °C. We find that the enhanced adhesion strength between metal nanoclusters and the sulfur-doped carbon support, which arises from the interfacial metal-sulfur bonding, greatly retards both metal atom diffusion and nanocluster migration. In catalyzing propane dehydrogenation at 550 °C, the sulfur-doped carbon supported Pt nanocluster catalyst with interfacial electronic effects exhibits higher selectivity to propene as well as more stable durability than sulfur-free carbon supported catalysts., The sulfur is a documented poison reagent for metal catalysts. Here the authors show when doped in a carbon matrix, sulfur can enhance the adhesion strength and eventually suppress the metal sintering, which improve the performance of propane dehydrogenation by strong chemical/electronic interactions.

Summary Creating free-access active sites and regulating their interaction with substrates are crucial for efficient catalysis, yet remain a grand challenge. Herein, naked Pd nanoparticles (NPs) have been encapsulated in a metal-organic framework (MOF), MIL-101-NH2, to afford Pd@MIL-101-NH2. The hydrophobic perfluoroalkyls were post-synthetically modified onto -NH2 group to yield Pd@MIL-101-Fx (x = 3, 5, 7, 11, 15), which engineer the MOF pore walls to regulate Pd surrounding microenvironment and interaction with substrates. As a result, both the dehydrogenation coupling of organosilane and hydrogenation of halogenated nitrobenzenes show that their activity and selectivity can be greatly promoted upon hydrophobic modification due to the favorable substrate enrichment and regulated interactions between Pd and the modified MOF hosts, far surpassing the traditional supported or surfactant-protected Pd NPs. We envision metal NPs@MOF composites would be an ideal platform integrating the inherent activity of well-accessible metal sites with engineered microenvironment via readily tunable MOFs.

Strong metal–support interaction (SMSI) has long been studied in catalytic reactions. Proper utilization of the SMSI effect might not only improve the stability of the catalysts, but also the activity and selectivity. In this work, using the atomic layer deposition (ALD) technique, we synthesized a series of Pd/ZnO catalysts with Pd particle sizes ranging from 1.6 to 7.9 nm. Upon H2 reduction at elevated temperatures, these Pd/ZnO catalysts display a size-dependent SMSI effect wherein the larger-size Pd particles are more prone to be encapsulated by ZnO compared to the smaller ones. In the reaction of CO2 hydrogenation, we show that such size-dependent SMSI, together with the size-related CO binding strength on Pd particles, provides a higher activity and methanol selectivity to the Pd particles larger than ~2.5 nm.

Efficient conversion of light alkanes is of essential significance for enhancing the utilization efficiency of resources and exploring the activation and evolution regulation of C-C and C-H bonds in stable molecules. The processes are often executed with catalysts under harsh conditions. The olefin yield and metal stability have been the long-standing concerns. Herein, we report a facile strategy of constructing a bifunctional Pt/HZSM-5-based catalyst by two-step atomic layer deposition (ALD) to achieve a high light olefin formation rate of 0.48 mmol gcat-1·min-1 in the catalytic cracking of n-butane at 600 °C, which is ∼2.2 times higher than that of the conventional Pt/HZSM-5 catalyst (0.22 mmol gcat-1·min-1). Moreover, the bifunctional Pt/HZSM-5-based catalyst exhibited outstanding recyclability and excellent metal stability against sintering in comparison with conventional Pt/HZSM-5. Detailed microscopic and spectroscopic characterization studies demonstrate that the metal oxide (TiO2 or Al2O3) coating not only prevents the metal from high-temperature sintering, but also regulates the proportion of coordinately unsaturated platinum surface atoms. Theoretical calculations further confirm the preference of nucleation of TiO2 or Al2O3 on coordinately unsaturated platinum sites, which in turn modulates the bifunctional dehydrogenation-cracking pathway to improve the olefin formation rate.

Local coordination environments of isolated metal atoms in single-atom catalysts (SACs) play decisive roles for their catalytic performance. By varying the morphology and P and N heteroatom doping of the CeO2 support, here we showed that the activity of Pt single atoms on spherical CeO2 is about 7 times higher than that on CeO2 nanorods in hydrogenation of phenylacetylene. Doping the spherical CeO2 support using N is more effective than using P, and could enhance the activity by another 3.3 times, which was 2.6-times even higher than that of spherical CeO2 supported Pt clusters. Diffuse reflectance infrared Fourier transform spectroscopy of chemisorbed CO and X-ray photoelectron spectroscopy showed that N doping induced an increase of the electron density of Pt single atoms, opposite to the effect of P doping. H–D exchange and temperature-programmed reduction of hydrogen revealed that a large enhancement of hydrogen dissociation activity and hydrogen spillover by N doping are both essential for promoting the activity for catalytic hydrogenation.

Catalyst precise synthesis at the atomic level is of great importance for establishing structure–activity relationships and developing advanced catalysts with high efficiency. Atomic layer deposition (ALD) relies on sequential self-limiting molecular surface reactions on substrates. Such unique features not only ensures to achieve uniform deposition on powder surfaces with high surface areas, but also offers a powerful capability of control of the deposited materials with near atomic precision. This perspective will discuss new opportunities in atomically-precise synthesis of heterogeneous catalysts using ALD. As examples, I will describe the recent key developments in ALD synthesis of supported metal single atoms, homonuclear and heteronuclear dimers, bimetallic nanoparticles as well as atomically-dispersed metal (hydro)oxide species on metal nanoparticles to form 3-dimentional metal–oxide interfaces. Such atom-by-atom construction of supported catalysts from the bottom up is hardly achieved by other synthetic methods, thus would greatly deepen atomic-level understanding of structure–activity relationships. Given the rapid development of technologies in ALD coating on powders at a large scale, atom-by-atom synthesis of heterogeneous catalysts using ALD sheds dawn light on precise catalysis for industrial applications in the near future.

Selective semihydrogenation of alkynes has been a long-term and significant target, yet it remains a great challenge. Herein, bimetallic nanoparticles in a metal–organic framework (MOF), i.e., CuPd...