Supported Metal Catalysts Research Articles

Metal-support interactions in metal oxide-supported atomic, cluster, and nanoparticle catalysis.

Supported metal catalysts are essential to a plethora of processes in the chemical industry. The overall performance of these catalysts depends strongly on the interaction of adsorbates at the atomic level, which can be manipulated and controlled by the different constituents of the active material (i.e., support and active metal). The description of catalyst activity and the relationship between active constituent and the support, or metal-support interactions (MSI), in heterogeneous (thermo)catalysts is a complex phenomenon with multivariate (dependent and independent) contributions that are difficult to disentangle, both experimentally and theoretically. So-called "strong metal-support interactions" have been reported for several decades and summarized in excellent review articles. However, in recent years, there has been a proliferation of new findings related to atomically dispersed metal sites, metal oxide defects, and, for example, the generation and evolution of MSI under reaction conditions, which has led to the designation of (sub)classifications of MSI deserving to be critically and systematically evaluated. These include dynamic restructuring under alternating redox and reaction conditions, adsorbate-induced MSI, and evidence of strong interactions in oxide-supported metal oxide catalysts. Here, we review recent literature on MSI in oxide-supported metal particles to provide an up-to-date understanding of the underlying physicochemical principles that dominate the observed effects in supported metal atomic, cluster, and nanoparticle catalysts. Critical evaluation of different subclassifications of MSI is provided, along with discussions on the formation mechanisms, theoretical and characterization advances, and tuning strategies to manipulate catalytic reaction performance. We also provide a perspective on the future of the field, and we discuss the analysis of different MSI effects on catalysis quantitatively.

Catalytic dehydrogenation for hydrogen production controlled by metal-supported heterogeneous catalysts

Dehydrogenation is a chemical reaction that produces value-added hydrogen-deficient chemical compounds with hydrogen molecules that can be ubiquitously used in chemical industries.

Effect of Fe, Ni, and Co on the hydrothermal liquefaction of Chinese herb residue for bio-oil production

This study investigated the effects of reaction temperature (300–360 °C), reaction time (0–60 min), and the ratio of raw materials to solvent (1:5–1:15; g/mL) on the HydroThermal Liquefaction (HTL) of Chinese Herb Residues (CHR) for Bio-Oil (BO) production. Optimal HTL conditions for CHR were determined. To enhance both the yield and quality of BO, metal-modified catalysts including Fe/MCM-41, Co/MCM-41, and Ni/MCM-41 were prepared. These catalysts, after hydrogen reduction, loaded metal elements in their elemental state onto the carrier. Subsequently, CHR catalytic HTL experiments were conducted at 330 °C for 15 min with a ratio of 1:10 (g/mL). BO analysis was performed using EA, GC-MS, and FT-IR. Under the optimal HTL conditions (330 °C/15 min/1:10), the BO yield reached 24.57 wt.%, with a Higher Heating Value (HHV) of 25.96 MJ/kg. The major components of the BO included phenols, ketones, acids, and esters. In the catalytic HTL, Fe/MCM-41 (26.15 wt.%), Ni/MCM-41 (26.2 wt.%), and Co/MCM-41 (27.05 wt.%) catalysts each achieved higher BO yields. When using Ni/MCM-41 catalyst, the highest HHV of BO reached 32.01 MJ/kg, representing an 81% improvement over CHR HHV of 17.66 MJ/kg. Additionally, with Fe/MCM-41 catalyst, the lowest oxygen content in BO was 9.68%, and the selectivity for phenols and ketones was the highest, showing increases of 15.22% and 33.15%, respectively, reaching 44.13% and 24.5%. The results indicate that HTL can effectively convert high-moisture CHR into valuable products. Hydrogen-reduced metal-modified catalysts contribute significantly to increasing BO yield, promoting deoxygenation and hydrogenation reactions, and markedly improving HHV and the selectivity of chemical components, thereby effectively enhancing both the yield and quality of BO.

Synthesis of some derivatives of 1,8-dioxo-octa-hydro xanthene and 9-aryl-hexahydro acridine-1,8-dione using metal ion-exchanged NaY zeolite as heterogeneous catalyst.

A method for synthesizing xanthene and acridine derivatives using transition metal catalysts supported by de-alumination zeolite-NaY is described. Some transition metal ion-exchanged NaY zeolite was prepared and evaluated in a reaction toward the synthesis of xanthene and acridine. The most active catalyst in this field is a heterogeneous copper/zeolite catalyst. The synthesis of xanthene with a wide range of aldehydes/dimedone with a molar ratio of 1/2 and acridine synthesis with a molar ratio of dimedone/aromatic/ammonium nitrate of 2/1/1 was carried out in one pot and solvent-free conditions. Sensing in the presence of supported metal catalysts is operationally simple, does not require expensive or toxic reagents, and gives high yields in a short period.

Activating S surfaces by reversing the electron supply direction for fast hydrogen sensing

The nature of a built-in electric field within supported metal catalysts plays a crucial role in regulating gas adsorption and electron transfer during the gas-sensing process.

Ceria-based supported metal catalysts for the low-temperature water-gas shift reaction

Water-gas shift (WGS) reaction is a crucial step for the industrial production of hydrogen or upgrading hydrogen generated from fossil or biomass sources by removing the residual CO. However, current...

External [1 1 1] facets on nanorod gamma alumina boosts catalytic reductive amination of carbonyl compound to primary amine

Hydrogen spillover had played a significant role in catalytic processes involving reducible oxide supported metal catalyst and hydrogen molecule. Herein, crystal plane regulative hydrogen spillover strategy for the effective reductive amination on Ni/Al2O3 was developed. A rod-like alumina supported Ni catalyst with primarily external (111) facets was prepared. In the presence of NH3 and H2, Ni/Al2O3 (111) exhibited a turnover number of 30.4 h−1, which was 136-fold higher than that of Ni/Al2O3 (110) in the reductive amination of furfural to furfuryl amine. For the Ni/Al2O3 (111) catalyst, Al2O3 (111) facets exhibited strong Lewis acidity, resulting in an enhanced H affinity of Al2O3 (111) and a positively charged of Ni through electronic interaction. It was revealed that strong H affinity of Al2O3 (111) and positively charged Ni sites significantly promoted hydrogen migration from Ni surface to Al2O3 (111) facets, which effectively prevented the Ni sites from hydrogen poisoning and enhanced the adsorption and activation of NH3 and intermediates for reductive amination. Consequently, the activation energy of Schiff base reductive ammonolysis was obviously reduced, resulting in high inherent activity for furfural reductive amination to furfuryl amine. This work developed a new strategy for high efficiency reductive amination catalyst in terms of hydrogen spillover effect.

Enhanced Methanol Synthesis over Self-Limited ZnOx Overlayers on Cu Nanoparticles Formed via Gas-Phase Migration Route.

Supported metal catalysts are widely used for chemical conversion, in which construction of high density metal-oxide or oxide-metal interface is an important means to improve their reaction performance. Here, Cu@ZnOx encapsulation structure has been in situ constructed through gas-phase migration of Zn species from ZnO particles onto surface of Cu nanoparticles under CO2 hydrogenation atmosphere at 450 °C. The gas-phase deposition of Zn species onto the Cu surface and growth of ZnOx overlayer is self-limited under the high temperature and redox gas (CO2 /H2 ) conditions. Accordingly, high density ZnOx -Cu interface sites can be effectively tailored to have an enhanced activity in CO2 hydrogenation to methanol. This work reveals a new route for the construction of active oxide-metal interface and classic strong metal-support interaction state through gas-phase migration of support species induced by high temperature redox reaction atmosphere.

Tailored synthesis of plate-like SAPO-11 molecular sieve and its application in non-noble metal-supported catalyst for efficient hydroisomerization of long-chain n-alkanes

The tailored synthesis of plate-like SAPO-11 molecular sieve was achieved by introducing seed-surfactant directing agent into the synthesis system for the first time. The effects of morphological change of SAPO-11 molecular sieve on the physicochemical properties of SAPO-11 and the active phase properties of the catalyst were analyzed via a series of characterization techniques. The hydroisomerization of n-hexadecane was used as the model reaction to evaluate the catalytic performance of NiWS supported catalysts based on SAPO-11 molecular sieve with different morphologies. The plate-like SAPO-11 possessed better textural properties and acidity than pseudo-spherical SAPO-11. Meanwhile, the stacking number, dispersion and metal sulfidation degree of the active phase of sulfided NiW/SAPO-11-P were improved, and its high proportion of type II active phase optimized the metal–acid synergistic catalytic mechanism. Through tracking and analyzing the crystallization process of plate-like SAPO-11, the formation mechanism of plate-like SAPO-11 was investigated and revealed. The adsorption kinetics, diffusion behavior and catalytic kinetics of n-hexadecane on the catalysts were emphatically investigated. The optimized support structure and active phase properties improved the intrinsic catalytic activity and hydroisomerization reaction path priority of NiW/SAPO-11-P. It was found that the hydroisomerization reaction on NiW/SAPO-11-P was carried out under the reaction-limiting conditions, while the hydroisomerization reaction on NiW/SAPO-11-C was carried out under the reaction-controlling conditions. The effects of plate-like SAPO-11 on the activity stability of the catalyst was investigated, and the essential reasons for the differences in activity stability of the catalysts were revealed through comprehensively analyzing the coke formation difference and diffusion behavior difference. It is expected to provide reference for the tailored design of SAPO-11 molecular sieve with special morphology and the preparation of efficient hydroisomerization catalyst.

Preparation of porous metakaolin-based alkali-activated materials by microwave curing as supports for non-noble metal catalysts

Generally, alkali activated materials (AAMs) are prepared by curing an alkaline paste via conventional methods such as at room temperature for weeks, even months, or in oven for days to achieve the required properties. In this paper, fast electromagnetic radiation (microwaves) was investigated in detail as an alternative to conventional methods to produce environmentally friendly porous metakaolin-based AAMs as supports for catalysts (MK-AAMs). Hydrogen peroxide was used as a foaming agent to achieve porosity of the porous MK-AAMs. The non-porous MK-AAMs without a foaming agent were used as reference for the porous MK-AAMs. Curing of the MK-AAMs were conducted at room temperature (CU1), in an oven (CU2), and by microwaves (CU3). The specific surface area (SSA) of porous and non-porous MK-AAMs cured via CU1–3 was 36, 49, 90 m2/g and 9.0, 23, 24 m2/g, respectively. The average compressive strength (MPa) was 3.8, 2.7, 2.1 and 8.9, 6.4, 5.2, respectively. The catalytical performance of porous and non- porous MK-AAMs with Cu-catalyst (i.e., Cu-composites) were tested with an aqueous solution of bisphenol A (BPA) in catalytic wet air oxidation (CWAO). After 5 h of oxidation, the highest BPA conversion of 97 % was achieved with the porous Cu-composites. A slight mass loss of 1.5 wt % was observed in the Cu composites due to erosion caused by strong fluid flow in the CWAO experiments. Based on the various analyzes performed, no significant structural or chemical changes were observed in porous and non-porous MK-AAMs regardless of the curing method of CU1–3, which also confirmed that MK-AAMs can be produced by microwaves without losing the desired properties of the materials, such as porosity and mechanical durability.

Insight into Controllable Metal-Support Interactions in Metal/Metal Electrocatalysts for Efficient Energy-Saving Hydrogen Production.

Controllable metal-support interaction (MSI) modulations have long been studied for improving the performance of catalysts supported on metal oxides. However, the corresponding in-depth study for metal1-metal2 (M1-M2) composited configurations is rarely achieved due to the lack of reliable models and manipulation mechanisms of MSI modifications. We modeled ruthenium on copper support (Ru-Cu) metal catalysts with negligible interfacial contact potential (e0.06 V) and investigated MSI-dependent hydrogen evolution reaction (HER) catalysis kinetics induced by an electronic hydroxyl (HO-) modifier. Comprehensive simulations and characterizations confirmed that adjusting the HO- coverage can readily realize the tailorable improvement of MSI, facilitating charge migration at the Ru-Cu interface and optimizing the overall HER pathway on active Ru. As a result, a 5/10 monolayer (ML) HO-modified catalyst (5/10 ML) exhibits superior HER activity and durability owing to the relatively stronger MSI. This catalyst also ensured sustainable and efficient hydrogen generation in a urea electrolyzer with significant energy savings. Our work provides a valuable reference for optimizing the MSI-activity relationship in M1-M2 catalysts that target more than just HER.

Confinement Engineering of Zinc Single-Atom Triggered Charge Redistribution on Ruthenium Site for Alkaline Hydrogen Production.

Optimizing the interaction between metal and support in the supported metal catalysts effectively refines the electronic structure and boosts the catalytic properties of loaded active components. Herein a method is introduced to confine ultrafine ruthenium (Ru) nanoparticles within atomically dispersed Zn-N4 sites on a N-doped carbon network (Ru/Zn-N-C) through the strong electronic metal-support interaction, achieving superior catalytic activity and stability for alkaline hydrogen evolution. Spectroscopic data and theoretical modeling elucidate that the remarkable catalytic performance of Ru sites stems from their strong electronic coupling with neighboring Zn-N4 moiety and pyridinic N/pyrrolic N. This interaction induces an electron-deficient state of Ru, thereby accelerating the dissociation of H2 O and lowering the energy barriers for the desorption of OH* and H*. This insight provides a deeper understanding of the catalytic mechanisms at play. Furthermore, alkaline water electrolyzer using this catalyst as cathode delivers a mass activity of 3Amgcat -1 at 2.0V, much surpassing Ru-C. This research opens a novel pathway for the development of advanced materials , tailored for energy storage and conversion applications.

EFFECTIVE POLYMER DECORATION ON NICKEL-IMINE COMPLEX TO ENHANCE CATALYTIC HYDROGEN EVOLUTION

Since fossil fuels are rapidly depleting, finding alternative energy sources is becoming increasingly important. Among these alternatives, hydrogen (H2) is the most viable option. In hydrogen evolution systems, supported metal catalysts enhance the catalytic activity in the hydrolysis reaction by increasing the surface area. Therefore, this research focuses on preparing three different polymer-decorated Nickel-Imine complex catalysts (Ni@EC, Ni@EC-250, Ni@ECM) to improve their efficiency. To achieve the catalysts, a Nickel-Imine complex [1] was supported on three different polymers (EC, EC-250, and ECM). The catalysts (Ni@EC, Ni@EC-250, Ni@ECM) were then utilized to generate hydrogen from NaBH4 hydrolysis. The hydrogen evolution rates for Ni@EC, Ni@EC-250, and Ni@ECM catalysts were found as 6879; 15576; 8830 and 15459; 28689; 23417 mL H2 gcat-1.min-1, respectively at 30 oC and 50 oC. Results indicate that the Ni@EC-250 catalyst exhibited the best activity. Consequently, the subsequent steps of the catalytic hydrolysis reaction were studied using Ni@EC-250. The activation energy of the Ni@EC-250 catalyst was estimated at 39.255 kJ.mol-1. The reusability tests demonstrate that Ni@EC-250 remains active in sodium borohydride hydrolysis even after five runs. Technical abbreviations are defined upon first use. This study elucidates the reaction mechanism and kinetic data of catalytic sodium borohydride hydrolysis at various temperatures.

In Situ Visualization and Mechanistic Understandings on Facet-Dependent Atomic Redispersion of Platinum on CeO2.

Redispersion is an effective method for regeneration of sintered metal-supported catalysts. However, the ambiguous mechanistic understanding hinders the delicate controlling of active metals at the atomic level. Herein, the redispersion mechanism of atomically dispersed Pt on CeO2 is revealed and manipulated by in situ techniques combining well-designed model catalysts. Pt nanoparticles (NPs) sintered on CeO2 nano-octahedra under reduction and oxidation conditions, while redispersed on CeO2 nanocubes above ∼500 °C in an oxidizing atmosphere. The dynamic shrinkage and disappearance of Pt NPs on CeO2 (100) facets was directly visualized by in situ TEM. The generated atomically dispersed Pt with the square-planar [PtO4]2+ structure on CeO2 (100) facets was also confirmed by combining Cs-corrected STEM and spectroscopy techniques. The redispersion and atomic control were ascribed to the high mobility of PtO2 at high temperatures and its strong binding with square-planar O4 sites over CeO2 (100). These understandings are important for the regulation of atomically dispersed platinum catalysts.

Atomic-Scale 3D Structure of a Supported Pd Nanoparticle Revealed by Electron Tomography with Convolution Neural Network-Based Image Inpainting.

Electron tomography based on scanning transmission electron microscopy (STEM) is used to analyze 3D structures of metal nanoparticles on the atomic scale. However, in the case of supported metal nanoparticle catalysts, the supporting material may interfere with the 3D reconstruction of metal nanoparticles. In this study, a deep learning-based image inpainting method is applied to high-angle annular dark field (HAADF)-STEM images of a supported metal nanoparticle to predict and remove the background image of the support. The inpainting method can separate an 11nm Pd nanoparticle from the θ-Al2O3 support in HAADF-STEM images of the θ-Al2O3-supported Pd catalyst. 3D reconstruction of the extracted images of the Pd nanoparticle reveals that the Pd nanoparticle adopts a deformed structure of the cuboctahedron model particle, resulting in high index surfaces, which account for the high catalytic activity for methane combustion. Using the xyz coordinate of each Pd atom, the local Pd-Pd bond distance and its variance in a real supported Pd nanoparticle are visualized, showing large strain and disorder at the Pd-Al2O3 interface. The results demonstrate that 3D atomic-scale analysis enables atomic structure-based understanding and design of supported metal catalysts.

Supported Nickel‐based Catalysts for Heterogeneous Hydrogenation of Aromatics

AbstractAromatic hydrocarbons are carcinogenic and can induce mutations in living organisms, posing a threat to the ecological environment and human life and health. Catalytic hydrogenation of aromatics to reduce the saturation of aromatics not only reduces their toxicity, but also greatly increases their potential value. Compared with the unsupported catalysts with only active components, the supported metal catalysts have higher catalytic activity and better selectivity, the catalytic activity of the hydrogenation reaction depends on the metal active phase and catalyst support. On metal/acid catalysts, the metal active center and nearby acid sites are involved in the conversion of aromatics, the active hydrogen leaking from the metal center can hydrogenate the adsorbed aromatics at the acid site. This paper reviews the recent research progress of nickel‐based catalysts for aromatic hydrocarbon catalytic hydrogenation and discusses the development prospects and challenges faced by non‐precious metal catalysts. In addition, the sulfur tolerance and hydrogen storage properties of catalysts for aromatics are reviewed.

One stone, three birds strategy for synthesis of N-doped activated carbon-supported surface-enriched and redispersed Pd NPs via plasma for formic acid dehydrogenation

Rational design of supported Pd catalysts with excellent performance for H2 production via inexpensive and sustainable formic acid (FA) dehydrogenation remains challenging. N-doped activated carbon (AC)-supported surface-enriched and redispersed Pd nanoparticles (Pd/ACCP (250 W, 10 min)) with enhanced performance for FA dehydrogenation were prepared via plasma-assisted thermal reduction (input power: 250 W, discharge time: 10 min). The TOFinitial (initial turnover frequency) of Pd/ACCP (250 W, 10 min) reached 1276 h−1, and gas generation over it for the first and third reaction cycles was 1.11 and 1.52 times higher, respectively, than that of Pd/ACC and 1.25 and 12.40 times higher, respectively, than that of Pd/AC (Sigma–Aldrich). Characterization results indicated that Pd/ACCP (250 W, 10 min) had surface-enriched and redispersed Pd species, owing to the plasma etching and strong electric field, large specific surface area, small Pd particle size, and high Pd/C atomic ratio. Enhanced N doping of AC was achieved via plasma treatment, and N mainly existed as highly active pyridine nitrogen. The plasma-based strategy yielded Pd/ACCP (250 W, 10 min) with excellent catalytic performance for FA dehydrogenation. This study provides insights into plasma-controllable synthesis of supported metal catalysts and delivers a new rational design concept of FA dehydrogenation catalysts.

Mechanistic study of oxygen reduction reaction on a Pd/CeO2-ZrO2 catalyst

Three-way catalysts (TWCs) are widely used to convert the exhaust gases produced by internal combustion engines, including hydrocarbons, CO, and NOx, into harmless gases such as CO2, N2, and H2O. TWCs mainly consist of a metal catalyst, catalyst support, and ceramic substrate, and their performance is known to be closely related to the oxygen storage capacity (OSC) of the ceramic substrates. However, oxygen storage is a complex multi-step process that is not yet fully understood. In this study, we visualized oxygen storage at the Pd/CeO2–ZrO2 (CZ) interface in the practical operating temperature range of TWCs using oxygen isotope quench techniques and elucidated the detailed reaction mechanism using density functional theory calculations. Pd supported on CZ promotes the incorporation of oxygen into the CZ surface. In addition, our investigation of the transport behavior of the incorporated oxygen in the bulk regime reveals that the bond strength between oxygen and surrounding atoms is weakened by Zr doping, resulting in more facile oxygen vacancy formation and oxygen migration. Our results provide useful insights that will guide the future design of highly active TWCs.

Enhanced oxygen reduction catalytic performance of PtNi alloy through modulating metal–support interaction

Tuning metal–support interaction had been regarded as an effective strategy to adjust the electronic structure, catalytic activity and durability of supported metal catalysts. Herein, we design PtNi alloy on nitrogen-doped carbon and SnO2 dual-support and modulate the metal–support interaction. SnO2/PtNi/NC presents strongly coupled SnO2-PtNi-NC interface with lattice overlap of SnO2 (200), Pt (111), Pt (200), and graphitized carbon, along with enhanced electron transfer. SnO2/PtNi/NC has an improved catalytic activity and enhanced stability for oxygen reduction reaction. SnO2/PtNi/NC catalyst had a half-wave potential of 0.886 V versus reversible hydrogen electrode (RHE) in an acidic solution, higher than PtNi/NC (0.785 V vs. RHE) and commercial Pt/C (0.846 V vs. RHE). Furthermore, the current retention of SnO2/PtNi/NC (87.3 %) is also larger than that of commercial Pt/C (56.8 %) and PtNi/NC (19.8 %) after 1000 times start-stops. This study sheds light on the understanding effect of metal–support interaction on the durability of heterogeneous electrocatalysts.

Hydrogenated borophene enabled synthesis of multielement intermetallic catalysts

Supported metal catalysts often suffer from rapid degradation under harsh conditions due to material failure and weak metal-support interaction. Here we propose using reductive hydrogenated borophene to in-situ synthesize Pt/B/C catalysts with small sizes (~2.5 nm), high-density dispersion (up to 80 wt%Pt), and promising stability, originating from forming Pt-B bond which are theoretically ~5× stronger than Pt-C. Based on the Pt/B/C module, a series (~18 kinds) of carbon supported binary, ternary, quaternary, and quinary Pt intermetallic compound nanocatalysts with sub-4 nm size are synthesized. Thanks to the stable intermetallics and strong metal-support interaction, annealing at 1000 °C does not cause those nanoparticles sintering. They also show much improved activity and stability in electrocatalytic oxygen reduction reaction. Therefore, by introducing the boron chemistry, the hydrogenated borophene derived multielement catalysts enable the synergy of small size, high loading, stable anchoring, and flexible compositions, thus demonstrating high versatility toward efficient and durable catalysis.