Weak Metal-support Interaction Research Articles

Suppression of inactive sites in NiMo@amorphous alumina catalysts for hydrodesulfurization reaction: Effect of Ga doping

Hydrodesulfurization (HDS) reaction activity depends on the formation of active NiMoS (completely sulfided multilayer type 2 sites) and inactive NiAl2O4/NixSy phases on the catalyst surface. These inactive phases not only itself inactive for the reaction but also hinder the formation of active NiMoS phases. In addition, the formation of strong Mo-O-Al bonds also lowers the reducibility of the catalyst, suggesting lesser catalytic activity (type 1 sites, partially sulfided single-layer sites). To this end, we report the formation of NiMo/Ga doped amorphous alumina (A-Al2O3) catalysts prepared by the colloidal synthesis method. A-Al2O3 was chosen as a support because it has lower surface energy, better physicochemical properties, and enhanced acidic sites than the crystalline alumina phase, which favours the formation of type 2 sites or weak metal-support interaction (completely sulfided multilayer NiMoS sites). Further, the Ga doping in A-Al2O3 support substitute the tetrahedral Al sites and form GaAl2O4 phases by reducing NiAl2O4 inactive sites, and the free Ni decorate the edges of MoS2 to form HDS active NiMoS sites. Therefore, NiMo/Ga doped A-Al2O3 catalyst (at 1 wt% Ga loading) reported enhanced HDS catalytic activity (25%), HDS reaction rate constant (kHDS-2.15 times) and turn over frequency (TOF-1.3 times) than the conventional NiMo/γ-Al2O3 catalysts.

Effect of preparation conditions of nanocrystalline Pd/MgO catalysts on their performance in selective hydrogenation of acetylene

In the present work, an alkoxide sol-gel method was applied to prepare Pd/MgO catalysts. The sol-gel procedure was followed by supercritical drying (aerogels) or conventional drying (xerogels) in a furnace. These materials were compared with the impregnated samples. The Pd loading was 1 wt% in all the cases. The as-prepared catalysts were characterized by a set of physicochemical methods. Both the type of the Pd precursor and the preparation route were found to affect the porous structure of the materials as well as the dispersion of the palladium particles and their localization over the MgO support. Both the xerogel and incipient wetness impregnation methods lead to a narrower pore size distribution in comparison to the aerogel technique. The most dispersed particles with an average size of ∼ 2.0–2.2 nm were observed for the samples prepared by xerogel and impregnation methods. In the case of aerogel-prepared samples, metallic palladium particles possess bimodal distribution with average diameters of 4.3 and 8.4 nm. The best catalytic performance in acetylene hydrogenation to ethylene (50 % acetylene conversion at 37 °C with selectivity ∼60 %) was observed for the Pd/MgO catalyst prepared via the aerogel route using [Pd(NH3)4](NO3)2. Compared to other samples, this material is characterized by relatively weak metal-support interactions and the availability of active sites for reactants, which ensures the kinetic mode of the hydrogenation reaction (Ea = 74.9 kJ/mol).

Unique role of silica in MOF-Derived High-Loading Palladium-on-Ceria single atom catalysts with excellent efficiency and durability

In most cases, the sintering tendency of supported metal single atoms could be attributed to the unstable structural characteristics of supports in demanding operating conditions, particularly for high-loading single-atom catalysts (SACs), ultimately resulting in deactivation. To address this issue, SiO2 is employed to enhance the structural stability of both supports and the supported Pd single atoms. SiO2 serves not only to prevent the collapse of support structures but also to promote the activation of surface oxygen species by facilitating electron transfer with the supports. This, in turn, establishes strong metal-support interactions (MSIs) to stabilize and activate atomically dispersed Pd species. Additionally, the electrons donated from Ce-O and Si-O to Pd atoms further catalyze the formation of oxygen vacancies, ultimately leading to significantly improved activity and durability in CO oxidation. Without SiO2, the instability of support structure, coupled with the weak MSIs, promotes the aggregation of Pd atoms, resulting in relatively lower catalytic activity and durability.

Enhancing photocatalytic H2 production and dye degradation: Comparative analysis of gold reduction techniques on Au/TiO2 nanocomposites

This study compares the impact of two reduction techniques, thermal reduction (TR) and photocatalytic reduction (PR), on Au/TiO2 photocatalysts synthesized using the deposition-precipitation with urea method. Characterization methods, including temperature-programmed reduction, UV-Vis diffuse reflectance spectroscopy, electrochemical assessments (open-circuit potential and linear sweep voltammetry), and transmission electron microscopy, were employed. The 2-h. PR treatment yielded a highly effective photocatalyst (0.5Au-PR2), with 93.6% of gold nanoparticles below 4 nm, outperforming the TR counterpart (76.8%). All Au-loaded samples exhibited an absorption band between 400 and 800 nm, indicating the localized surface plasmon resonance (LSPR) effect. Interestingly, the TR catalyst had a broader LSPR band than the PR catalyst. Additionally, the 0.5Au-PR2 sample showed higher photocurrent and superior photocatalytic activity in the degradation of methyl orange and hydrogen production, which is attributed to its smaller particle size (2.9 nm) and weaker metal-support interaction. This smaller particle size emphasizes the crucial role of reduction techniques in tailoring Au/TiO2 photocatalysts for enhanced performance.

Disclosing Support‐Size‐Dependent Effect on Ambient Light‐Driven Photothermal CO2 Hydrogenation over Nickel/Titanium Dioxide

AbstractThe size of support in heterogeneous catalysts can strongly affect the catalytic property but is rarely explored in light‐driven catalysis. Herein, we demonstrate the size of TiO2 support governs the selectivity in photothermal CO2 hydrogenation by tuning the metal‐support interactions (MSI). Small‐size TiO2 loading nickel (Ni/TiO2‐25) with enhanced MSI promotes photo‐induced electrons of TiO2 migrating to Ni nanoparticles, thus favoring the H2 cleavage and accelerating the CH4 formation (227.7 mmol g−1 h−1) under xenon light‐induced temperature of 360 °C. Conversely, Ni/TiO2‐100 with large TiO2 prefers yielding CO (94.2 mmol g−1 h−1) due to weak MSI, inefficient charge separation, and inadequate supply of activated hydrogen. Under ambient solar irradiation, Ni/TiO2‐25 achieves the optimized CH4 rate (63.0 mmol g−1 h−1) with selectivity of 99.8 %, while Ni/TiO2‐100 exhibits the CO selectivity of 90.0 % with rate of 30.0 mmol g−1 h−1. This work offers a novel approach to tailoring light‐driven catalytic properties by support size effect.

Disclosing Support-Size-Dependent Effect on Ambient Light-Driven Photothermal CO2 Hydrogenation over Nickel/Titanium Dioxide.

The size of support in heterogeneous catalysts can strongly affect the catalytic property but is rarely explored in light-driven catalysis. Herein, we demonstrate the size of TiO2 support governs the selectivity in photothermal CO2 hydrogenation by tuning the metal-support interactions (MSI). Small-size TiO2 loading nickel (Ni/TiO2 -25) with enhanced MSI promotes photo-induced electrons of TiO2 migrating to Ni nanoparticles, thus favoring the H2 cleavage and accelerating the CH4 formation (227.7 mmol g-1 h-1 ) under xenon light-induced temperature of 360 °C. Conversely, Ni/TiO2 -100 with large TiO2 prefers yielding CO (94.2 mmol g-1 h-1 ) due to weak MSI, inefficient charge separation, and inadequate supply of activated hydrogen. Under ambient solar irradiation, Ni/TiO2 -25 achieves the optimized CH4 rate (63.0 mmol g-1 h-1 ) with selectivity of 99.8 %, while Ni/TiO2 -100 exhibits the CO selectivity of 90.0 % with rate of 30.0 mmol g-1 h-1 . This work offers a novel approach to tailoring light-driven catalytic properties by support size effect.

Site-specific metal-support interaction to switch the activity of Ir single atoms for oxygen evolution reaction

The metal-support interactions (MSI) could greatly determine the electronic properties of single-atom catalysts, thus affecting the catalytic performance. However, the typical approach to regulating MSI usually suffers from interference of the variation of supports or sacrificing the stability of catalysts. Here, we effectively regulate the site-specific MSI of Ir single atoms anchored on Ni layered double hydroxide through an electrochemical deposition strategy. Cathodic deposition drives Ir atoms to locate at three-fold facial center cubic hollow sites with strong MSI, while anodic deposition drives Ir atoms to deposit onto oxygen vacancy sites with weak MSI. The mass activity and intrinsic activity of Ir single-atom catalysts with strong MSI towards oxygen evolution reaction are 19.5 and 5.2 times that with weak MSI, respectively. Mechanism study reveals that the strong MSI between Ir atoms and the support stimulates the activity of Ir sites by inducing the switch of active sites from Ni sites to Ir sites and optimizes the adsorption strength of intermediates, thereby enhancing the activity.

A Fluidizable Catalyst for N-Butane Oxidative Dehydrogenation under Oxygen-Free Reaction Conditions

This study evaluates the effectiveness of fluidizable VOx/MgO-γAl2O3 catalysts for C4-olefin production via n-butane oxidative dehydrogenation (BODH). Catalysts were prepared via vacuum incipient wetness impregnation and then characterized by employing several techniques such as BET (Brunauer–Emmett–Teller) method, XRD (X-ray diffraction), LRS (laser Raman spectroscopy), XPS (X-ray photoelectron spectroscopy), TPR/TPO (temperature-programmed reduction/temperature-programmed oxidation), NH3-TPD (temperature-programmed desorption), NH3 -desorption kinetics and pyridine-FTIR. The BET analysis showed the prepared catalysts’ mesoporous structure and high surface areas. The XRD, LRS and XPS established the desirable presence of amorphous VOx phases. The TPR/TPO analyses corroborated catalyst stability over repeated reduction and oxidation cycles. The NH3-TPD and NH3 desorption kinetics showed that the catalysts had dominant moderate acidities and weak metal-support interactions. In addition, Pyridine-FTIR showed the critical influence of Lewis acidity. The VOx/MgO-γAl2O3 catalysts were evaluated for BODH using a fluidized CREC Riser Simulator, operated under gas-phase oxygen-free conditions, at 5 to 20 s reaction times, and at 450 °C to 600 °C temperatures. The developed VOx/MgO-γAl2O3 catalysts demonstrated performance stability throughout multiple injections of butane feed. Catalyst regeneration was also conducted after six consecutive BODH runs, and the coke formed was measured using TOC (Total Organic Carbon). Regarding the various BODH catalyst prepared, the 5 wt% V-doped MgO-γAl2O3 yielded in a fluidized CREC Riser Simulator the highest selectivity for C4-olefins, ranging from 82% to 86%, alongside a butane conversion rate of 24% to 27%, at 500 °C and at a 10 s reaction time.

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.

Structural evolution of Ru/Te interaction for hydrogen generation engineered by proof of concept via carbon doping

Catalyst support with low conductivity and weak metal-support interaction is a tricky issue in advanced catalyst development. Herein, taking the semi-conductive Te nanorods supported Ru nanoparticles as an example, we proposed a proof of concept for carbon doping to engineer the Ru/Te interaction for efficient hydrogen evolution reaction (HER). It was found that the conventional approach for carbon layer formation over Te nanorods via glucose by hydrothermal approach (Te–C-1) was insufficient to boost the catalytic performance, but the deep carbonization via further thermal annealing of Te–C-1 can enhance the conductivity and metal-support interaction when supporting Ru nanoparticles (Ru/Te–C-2). The important conductivity and charge transfer ability improvement and strong electronic interaction were found by the electrochemical measurements and the spectroscopic analysis, probably resulting from the deep carbonization induced Te nanorods structure destruction and in-depth carbon doping. As a result, Ru/Te–C-2 showed a catalytic performance as good as the commercial Pt/C catalyst for HER, which required ultralow overpotentials of 39 and 34 mV to achieve 10 mA cm−2 in 0.5 M H2SO4 and 1.0 M KOH, respectively, when loaded on the glass carbon electrode; Besides, the catalytic kinetics, charge transfer ability, and catalytic efficiency were also improved due to the carbon doping effect; high catalytic stability was also indicated by the dynamic stability running for 2000 cycles and steady-state operation for 20 h in both acidic and alkaline media. Density-functional theory calculations show that carbon doping effectively promotes the electron transfer from Te to Ru, thus changing the electronic structure and the adsorption energy for H* adsorption, which facilitates the HER process. The current study showed the validation of carbon doping for enhanced metal-supporting interaction that will be instructive for conductivity improvement of the relevant catalyst in electrocatalysis reaction.

Boron-doping-induced modulation of structural parameters of pristine commercial carbon black for promoting Ru-catalyzed O[sbnd]H bond activation toward hydrogen evolution

Owing to the lack of adequate nucleation sites for metal nanoparticles (NPs) and weak metal-support interaction, pristine carbon materials supported metal NPs suffer from limited surface-exposed active sites and thereby low catalytic activity. Herein, we report a sodium borohydride-mediated modification of commercial Valcan carbon (VC) to produce B-doped VC (BVC) as a useful support to deposit Ru NPs (Ru/BVC) for hydrogen production from ammonia borane hydrolysis (ABH). The B-doping endows BVC with not only more surface functional groups and defect sites but also abundant meso/macroporous structure and hydrophilic surface, facilitating the generation of uniformly dispersed ultra-small Ru NPs (d = 1.42 nm) with strong electronic metal-support interaction. The optimal Ru/BVC catalyst exhibits an excellent activity with a turnover frequency of 1577.0 min−1 (depending on Ru dispersion). Isotopic and alkali promotion experiments unveil the rate-determining step (RDS) for ABH is the oxidative cleavage of the OH bond in water. The copious surface-exposed active sites and the regulated electron distribution between Ru NPs and BVC efficiently reduce the energy barrier for RDS, thereby promoting catalytic performance of hydrogen evolution from ABH. This simple and efficient heteroatom-doping strategy is easily extended to fabricate efficient catalysts with promoted performance for catalytic applications.

Weak Metal-Support Interaction over CuO/TiO2 Catalyst Governed Low-Temperature Toluene Oxidation.

Regulating the metal-support interaction is essential for obtaining highly efficient catalysts for the catalytic oxidation of volatile organic compounds (VOCs). In this work, CuO-TiO2(coll) and CuO/TiO2(imp) with different metal-support interactions were prepared via colloidal and impregnation methods, respectively. The results demonstrated that CuO/TiO2(imp) has higher low-temperature catalytic activity, with a 50% removal of toluene at 170 °C compared to CuO-TiO2(coll). Additionally, the normalized reaction rate (6.4 × 10-6 mol·g-1·s-1) at 160 °C over CuO/TiO2(imp) was almost four-fold higher than that over CuO-TiO2(coll) (1.5 × 10-6 mol·g-1·s-1), and the apparent activation energy value (27.9 ± 2.9 kJ·mol-1) was lower. Systematic structure and surface analysis results disclosed that abundant Cu2+ active species and numerous small CuO particles were presented over CuO/TiO2(imp). Owing to the weak interaction of CuO and TiO2 in this optimized catalyst, the concentration of reducible oxygen species associated with the superior redox property could be enhanced, thus significantly contributing to its low-temperature catalytic activity for toluene oxidation. This work is helpful in exploring the influence of metal-support interaction on the catalytic oxidation of VOCs and developing low-temperature catalysts for VOCs catalytic oxidation.

Modulation the metal-support interactions of potassium molybdenum-based catalysts for tuned catalytic performance of synthesizing CH3SH

Modulation of the metal-support interactions (MSI) is an effective means to improve the performance of supported catalysts, but the role of the metal-support effect in the synthesis of CH3SH from CO/H2/H2S mixtures has not been recognized. Here, three different interactions, namely weak MSI, strong MSI and electronic MSI are constructed over K-promoted MoS2-base catalysts and investigated for the synthesis of CH3SH. The catalytic activity experiments show that the K-Mo catalyst with strong MSI has the highest formation rate toward CH3SH, while the K-Mo catalyst with electronic MSI instead shows the worst formation rate toward CH3SH. The characterizations suggest that the strong MSI facilitates the enhancement of Mo-S bond strength and the production of few layers, shorter slab and ordered K-MoS2 particles. The former benefits the formation and stabilization of C-S intermediate species and subsequent hydrogenation to CH3SH, while the latter promotes the generation of more Mo-coordinatively unsaturated sites (Mo-CUS) and thus facilitates the first-step adsorption and activation of reactants. In contrast, electronic MSI weakens the strength of the Mo-S bond, which inhibits the generation of C-S intermediate species. On the other hand, the presence of electronic MSI leads to the generation of Mo-Ov-Ti interfacial sites, which is favorable for the hydrogenolysis of CH3SH to CH4. This work provides an insight into the construction and selection of metal-support interactions for heterogeneous catalysis.

Carbon nanotubes production from catalytic pyrolysis of polyethylene over nickel-based catalysts: The influence of support materials

To understand the influence of support materials on the reactivity of catalysts, four nickel- based catalysts supported on different materials (ZrO2, TiO2, Nb2O5, and Al2O3) were developed and investigated in the carbon nanotubes production from catalytic pyrolysis of polyethylene using two-stage fixed bed reactor. The results showed that the Ni/Al2O3 catalyst generated the highest carbon material yield of 36.5 wt%, while the order of carbon material yield was Ni/Al2O3 > Ni/TiO2 > Ni/ZrO2 > Ni/Nb2O5. To explore the correlation between catalysts properties and carbon products, the essential structural characteristics of fresh catalyst and reacted catalyst were analyzed by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (TEM), temperature program oxidation (TPO), nitrogen adsorption measurements and Raman spectroscopy. The Ni/Al2O3 catalyst with the highest surface area, abundant pore structure, and moderate metal-support interaction promoted the decomposition of pyrolysis volatiles to produce carbon nanomaterials, which were consist of carbon nanotubes (CNTs). CNTs are the main component of carbon materials produced, accounting for a relatively high proportion. In comparison, the large metal active particles and weak metal-support interaction of Ni/TiO2 catalyst had a negative impact on the formation of CNTs, generating many fishbone like carbon nanofibers (CNFs). Moreover, the poor pore structure and larger metal active particles for Ni/ZrO2 and Ni/Nb2O5 catalyst led to a low carbon deposition yield and poor quality of CNTs. The results provide valuable data and theoretical support for the research on the preparation of valuable carbon nanotubes from waste plastics.

Hydrogen production from hazardous petroleum sludge gasification over nickel-loaded porous ZSM-5 and Al2O3 catalysts under air condition

In this study, the potential of petroleum sludge (PS) for hydrogen production via the gasification process was evaluated. For this purpose, nickel (Ni)-loaded ZSM-5 and γ-Al2O3 (Ni-ZS and Ni–Al) catalysts were prepared and employed for PS gasification in air condition. The effects of different supports, Ni loading content, and reaction temperatures on the production of hydrogen-rich syngas along with the stability and reusability of the best catalyst were investigated. Applying 5%Ni-ZS obtained more gas yield (68.09 wt%) and hydrogen selectivity (25.04 vol%) compared to those obtained by 5%Ni–Al mostly owing to weak metal-support interactions which led to the dominance of well-dispersed metallic Ni. At various Ni loading percentages, 10%Ni-ZS showed the highest catalytic efficiency, which increased both gas yield (70.92 wt%) and hydrogen selectivity (30.74 vol%). However, excessive Ni content (especially 20%) significantly reduced the gas yield and hydrogen selectivity because of limited accessibility of support's active sites, poor dispersion of Ni, and inappropriate acidity. Increasing the temperature promoted the gas yield and produced hydrogen, where the highest gas yield (73.18 wt%) and hydrogen selectivity (33.15 vol%) were obtained at 850 °C due to the endothermic nature of gasification reactions. The 10%Ni-ZS catalyst showed proper stability during three consecutive experiments at 850 °C. The spent catalyst was successfully regenerated without a significant reduction in activity or selectivity.

CeO2-supported Fe, Co and Ni toward CO2 hydrogenation: Tuning catalytic performance via metal-support interaction

The chemical transformation of CO2 produces carbon compounds that can be used as precursors for the production of chemicals and fuels. Here, we investigated the activity and selectivity of the transition metals (Fe, Co, and Ni) supported on CeO2 catalyst for CO2 hydrogenation at atmospheric pressure. We found that Ni/CeO2 shows the highest CO2 conversion compared with Fe/CeO2 and Co/CeO2. Besides, Co/CeO2 and Ni/CeO2 exhibit nearly 100% CH4 selectivity while Fe/CeO2 inclines to produce CO. The characterization results show that the metal-support interaction order is Fe/CeO2 > Co/CeO2 > Ni/CeO2, the weak metal-support interaction over Ni/CeO2 benefits the activation of H2 and then promotes the activity of CO2 hydrogenation. Additionally, in situ DRIFTS results demonstrate that monodentate formate species rather than bidentate formate are the active intermediates. The main route of CO2 hydrogenation to CH4 is that CO2 is firstly transformed to m-HCOO∗ and then direct hydrogenation of the m-HCOO∗ to CH4. This study provides insights into the understanding of the mechanisms of CO2 hydrogenation on CeO2 based catalysts.

Effects of HY addition on NiMoS active phase of NiMo(NH3) impregnated NiMo/Al2O3-HY and its role in 4,6-dimethyl-dibenzothiophene hydrodesulfurization

Effects of HY addition on NiMoS active phase of NiMo(NH3) impregnated NiMo/Al2O3-HY and its role in 4,6-dimethyl-dibenzothiophene hydrodesulfurization was investigated. The results show that HY can promote HDS reaction by changing the morphology of NiMoS nanoclusters even when isomerization of 4,6-DMDBT is not involved. In the absence of strong acid sites, TOF of NiMo/Al2O3 catalyst was still improved by 90%. XRD, H2-TPR, Raman, TEM, and XPS characterization show that proper metal support interaction caused by HY addition is beneficial to the formation of large-scale multilayer NiNoS clusters, the enrichment of Ni in NiMoS clusters and the increase of NiMoS active sites, thereby leading HDS catalyst exhibiting highest intrinsic activity (TOF). However, too strong or too weak metal support interaction will reduce intrinsic activity for HDS catalysts. When pH value of impregnation solution is 10, the strong metal support interaction reduces layer numbers of NiMoS clusters. When pH value of impregnation solution is 11, negative charge hinders the formation of NiMoS clusters. This not only leads to a further decrease HYD pathway selectivity, but also significantly reduces the initial reaction rate of HDS catalyst.

Small-sized Ni nanoparticles embedded nickel phyllosilicate as a metal-acid bifunctional zeolite catalyst for cooperatively boosting CO2-CH4 reforming

Ni-based catalysts using siliceous materials as the supports have suffered from two challenging issues of sintering and carbon deposition for dry reforming of methane (DRM), resulted from a weak metal-support interaction. Given these, a novel metal–acid bifunctional Ni@S-1 zeolite catalyst is tailored from the evolution of hydroxylated nickel phyllosilicates that are formed by subtly controlling the coordination environments of Ni precursor complexes in the silicalite-1 (S-1) zeolite. The developed Ni0.44@S-1 catalyst renders almost equivalent CH4 and CO2 conversions (85.1 % and 88.7 %), high H2/CO molar ratio (about 1) and superb long-term stability during 100 h with no activity loss at 750 °C with a WHSV of 100 L·gcat−1·h−1, outperforming other control catalysts under investigation. Such superior catalytic behavior benefits from the synergy between highly uniform Ni nanoparticles (3–5 nm) confined in the micropores of zeolite and substantially formed Lewis acid sites due to coordinatively unsaturated Ni2+ sites located at the reduced 2:1 nickel phyllosilicate, as revealed by detailed characterizations. Meanwhile, it further discloses that a benign balance between formation and elimination of “process carbon” species is responsible for improving the carbon resistance of catalyst during the DRM reaction. The present design broadens a new insight for the development of new Ni-based catalysts with simultaneous coking- and sintering-resistant for the DRM application.

Impact of preparation method on nickel speciation and methane dry reforming performance of Ni/SiO2 catalysts.

The methane dry reforming reaction can simultaneously convert two greenhouse gases (CH4 and CO2), which has significantly environmental and economic benefits. Nickel-based catalysts have been widely used in methane dry reforming in past decade due to their low cost and high activity. However, the sintering and coke deposition of catalysts severely limit their industrial applications. In this paper, three Ni/SiO2 catalysts prepared by different methods were systematically studied, and the samples obtained by the ammonia evaporation method exhibited excellent catalytic performance. The characterization results such as H2-TPR, XPS and TEM confirmed that the excellent performance was mainly attributed to the catalyst with smaller Ni particles, stronger metal-support interactions, and abundant Ni-O-Si units on the catalyst surface. The anti-sintering/-coking properties of the catalyst were significantly improved. However, the Ni/SiO2-IM catalyst prepared by impregnation method had uneven distribution of nickel species and large particles, and weak metal-support interactions, showing poor catalytic performance in methane dry reforming. Since the nickel species were encapsulated by the SiO4 tetrahedral network, the Ni/SiO2-SG catalyst prepared by sol-gel method could not expose more effective active sites even if the nickel species were uniformly dispersed, resulting in poor dry reforming performance. This study provides guidance for the preparation of novel anti-sintering/-coking nickel-based catalysts.

Alloying Ni-Cu Nanoparticles Encapsulated in SiO2 Nanospheres for Synergistic Catalysts in CO2 Reforming with Methane Reaction.

In this work, we studied CO2 reforming with the methane (CRM) reaction over Ni-Cu alloy nanoparticles encapsulated in SiO2 nanospheres, for which combinational functions of alloy effect, size effect, metal-support interaction, and confinement effect exhibited high performance, good sintering resistance, and trace carbon deposition in CRM. The appropriate Cu-addition catalysts 0.2Cu-Ni@SiO2 and 0.5Cu-Ni@SiO2 had smaller NiCu alloy nanoparticles and a stronger metal-support interaction, exhibiting a better performance than the excessive Cu-addition catalysts 1.5Cu-Ni@SiO2 and 3Cu-Ni@SiO2 having Cu clusters and a weaker metal-support interaction. The best synergy of alloy effect, size effect, confinement effect, and metal-support interaction in the 0.5Cu-Ni@SiO2 catalyst contributed to the highest rates of CH4 and CO2 in CRM reported so far. This work demonstrates the importance of appropriate Cu addition in Ni-Cu@SiO2 catalysts, and the synergy for perfectly resolving sintering and carbon deposition in CRM.