Oxide Support Research Articles

13C Stable Isotope Tracing Reveals Distinct Fatty Acid Oxidation Pathways in Proliferative vs. Oxidative Cells.

The TCA cycle serves as a central hub to balance catabolic and anabolic needs of the cell, where carbon moieties can either contribute to oxidative metabolism or support biosynthetic reactions. This differential TCA cycle engagement for glucose-derived carbon has been extensively studied in cultured cells, but the fate of fatty acid (FA)-derived carbons is poorly understood. To fill the knowledge gap, we have developed a strategy to culture cells with long-chain FAs without altering cell viability. By tracing 13C-FA we show that FA oxidation (FAO) is robust in both proliferating and oxidative cells while the metabolic pathway after citrate formation is distinct. In proliferating cells, a significant portion of carbon derived from FAO exits canonical TCA cycle as citrate and converts to unlabeled malate in cytosol. Increasing FA supply or b-oxidation does not change the partition of FA-derived carbon between cytosol and mitochondria. Oxidation of glucose competes with FA derived carbon for the canonical TCA pathway thus promoting FA carbon flowing into the alternative TCA pathway. Moreover, the coupling between FAO and the canonical TCA pathway changes with the state of oxidative energy metabolism.

Regulating socketed geometry of nanoparticles on perovskite oxide supports for enhanced stability in oxidation reactions.

Heterogeneous catalysts with highly dispersed active particles on supports often face stability challenges during high-temperature industrial applications. The ex-solution strategy, which involves in situ extrusion of metals to form socketed particles, shows potential for addressing this stability issue. However, a deeper understanding of the relationship between the socketed geometry of these partially embedded nanoparticles and their catalytic performance is still lacking. Here, in situ transmission electron microscopy and theoretical calculations are utilized to investigate the oxygen-induced ex-solution process of Pd-doped LaAlO3 with varying concentrations of La vacancies (LaxAl0.9Pd0.1O3-δ). We find that the socketed geometry of Pd-based particles can be tuned by manipulating the levels of La deficiencies in the oxide support, which in turn influences the catalytic performance in high-temperature oxidation reactions. As for the socketed particles, the balance between particle size and outcrop height is crucial for determining the oxidation activity and sinter-resistance behavior. Consequently, the optimized catalyst, La0.8Al0.9Pd0.1O3-δ, exhibits superior catalytic performances, particularly high stability (still working after aging at 1000 °C for 50 h) and water resistance in various combustion reactions (e.g., CH4 oxidation and C3H8 oxidation).

Role of hydrogen spillover on the hydrogenation of N-ethylcarbazole over in-situ Encapsulation of Ru within zeolite for hydrogen storage

Hydrogen spillover plays a crucial role in heterogeneous catalysis, significantly enhancing the activity of catalysts. However, the promotion mechanism of hydrogen spillover on non-reducible oxide supports (such as zeolite) is rarely reported. Herein, we prepared Ru@Beta sample by in-situ approach, effectively encapsulating Ru species into Beta zeolite. Additionally, three samples (Ru/SiO2, Ru@Naβ, and Ru@Hβ) with different hydrogen spillover effect were prepared. The optimal concentration of Ru was 0.5 wt%, and the Ru@Hβ sample with the strongest hydrogen spillover has 100 % conversion rate of N-ethylcarbazole (NEC) and 98 % selectivity towards to 12H-NEC. In contrast, the Ru/SiO2 with weak hydrogen spillover has only 89.5 % conversion rate and 28.9 % selectivity of 12H-NEC. Notably, the Ru@Hβ can still completely convert NEC even after 7 cycles, thereby exhibiting its remarkable activity and stability. Various characterizations (HAADF-STEM, XPS, EXAFS, in-situ DRIFT, and H2-TPD) indicate the superior catalytic performance of Ru@Hβ with strong hydrogen spillover effect, originating from the presence of more hydroxyl (–OH) and Brønsted acid on the surface, while Lewis acid act as hydrogen acceptors and NEC hydrogenation sites. This work not only expands our understanding of the hydrogen spillover, but also paves the way onto the potential applications in heterogeneous catalysis for efficient hydrogenation.

FeCo Alloy-Decorated Proton-Conducting Perovskite Oxide as an Efficient and Low-Cost Ammonia Decomposition Catalyst

Ammonia is known as an alternative hydrogen supplier because of its high hydrogen content and convenient storage and transport. Hydrogen production from ammonia decomposition also provides a source of hydrogen for fuel cells. While catalysts composed of ruthenium metal atop various support materials have proven to be effective for ammonia decomposition, non-precious-metal-based catalysts are attracting more attention due to desires to reduce costs. We prepared a series of Fe, Co, Ni, Mn, and Cu monometallic catalysts and their alloys as catalysts over proton-conducting ceramics via the impregnation method as precious-metal-free ammonia decomposition catalysts. While Co and Ni showed superior performance compared to Fe, Mn, and Cu on a BaZr0.1Ce0.7Y0.1Yb0.1O3−б (BZCYYb) support as an ammonia decomposition catalyst, the cost of Fe is much lower than that of other metals. Alloying Fe with Co can significantly increase the conversion and stability and lower the overall cost of materials. The measured ammonia decomposition rate of FeCo/BZCYYb reached 100% at 600 °C, and the ammonia decomposition rate was almost unchanged during the long-term test of 200 h, which reveals its good catalytic activity for ammonia decomposition and thermal stability. When the metallic catalyst remained unchanged, BZCYYb also exhibited better performance compared to other commonly used oxide supports. Finally, when ammonia cracked using our alloy catalyst was fed to solid oxide fuel cells (SOFCs), the peak power densities were very close to that achieved with a simulated fully cracked gas stream, i.e., 75% H2 + 25% N2, thus proving the effectiveness of this new type of ammonia decomposition catalyst.

Nature of metal-support interaction for metal catalysts on oxide supports.

The metal-support interaction is one of the most important pillars in heterogeneous catalysis, but developing a fundamental theory has been challenging because of the intricate interfaces. Based on experimental ‎data, interpretable machine learning, theoretical derivation, and first-principles simulations, we established a ‎general theory of metal-oxide interactions grounded in ‎metal-metal and metal-oxygen interactions. The theory applies to metal nanoparticles and atoms on oxide supports and oxide films on metal supports. We found that for late-transition metal catalysts, metal-metal interactions dominated the oxide support effects and suboxide encapsulation over metal nanoparticles. A principle of strong metal-metal interactions for encapsulation occurrence is formulated and substantiated by extensive ‎experiments including 10 metals and 16 ‎oxides. The valuable insights revealed on (strong) metal-support interaction advance the interfacial design of supported metal catalysts.

An in Silico Investigation into Polyester Adsorption onto Alumina toward an Improved Understanding of Hydrogenolysis Catalysts.

Chemical recycling of end-of-life plastic wastes through hydrogenolysis is a promising pathway for achieving a circular plastics economy and reducing overall energy costs. Understanding molecular interactions at the inorganic-organic depolymerization interface is crucial for enhancing catalyst performance and overcoming challenges posed by mixed plastic waste streams. We investigated a fundamental step in the depolymerization process: physisorption of polymers onto the metal oxide support preceding diffusion to and reaction at the catalyst-support junction. Molecular dynamics simulations, augmented with well-tempered metadynamics, were conducted to explore the adsorption of polylactic acid (PLA) and polyethylene terephthalate (PET) oligomers onto a hydroxylated alumina support surface. Our findings revealed multiple layers of highly oriented solvent molecules (1,4-dioxane) above the surface, creating significant barriers to polyester adsorption. Disrupting and displacing these solvent layers led PET oligomers to adsorb closer to and interact stronger with the surface than PLA oligomers, possibly contributing to the higher reaction temperatures needed to achieve full conversion in PET versus PLA hydrogenolysis. We further suggest an experimental approach to validate our results of solvent layering behavior through predictions of X-ray reflectivity that are consistent with our initial experiments. The insights gained in this study can be leveraged to refine our understanding of catalytic mechanisms to predict depolymerization reactivity and selectivity and improve future hydrogenolysis catalyst designs.

Optimizing Cu 3d Bands with Nanotubular SnO2 to Boost Their Catalytic Transfer Hydrogenation Activity.

Catalytic transfer hydrogenation (CTH) using Cu nanocatalysts offers significant advantages over direct high-pressure hydrogenation. However, the active hydrogen (H*) in this process exhibits poor adsorption and tends to release H2 readily due to the fully occupied 3d states of Cu. To address this issue, a tubular SnO2 support with electron-accepting ability was selected to host Cu nanoparticles, aiming to optimize the Cu 3d bands. The Cu/SnO2 nanohybrids were prepared through an electrospinning technique, followed by hydrothermal synthesis. As evidenced by X-ray photoelectron spectroscopy (XPS) binding energy shifts and density functional theory (DFT) simulations, some electrons from Cu transferred to SnO2 in the Cu/SnO2 nanohybrids due to their different work functions. Such electron transfer enables the Cu 3d orbitals to lose electrons and alters its valence configuration from 3d10 to 3d10-x, which enhances the adsorption of active H* atoms and thereby inhibits undesirable H2 release. The 15 wt % Cu/SnO2 exhibits improved catalytic hydrogenation of 4-nitrophenol with NaBH4, with an optimal normalized rate constant of 56.98 mg-1 min-1 and a turnover frequency of 4.82 min-1, surpassing most reported catalysts. The enhanced activity is attributed to the optimized electronic states, improved hydrogen adsorption, and the tubular structure of the support. This work might shed light on developing more non-noble metal nanocatalysts for CTH by tuning their d bands with appropriate oxide supports.

Urea assimilation and oxidation support activity of phylogenetically diverse microbial communities of the dark ocean.

Urea is hypothesized to be an important source of nitrogen and chemical energy to microorganisms in the deep sea; however, direct evidence for urea use below the epipelagic ocean is lacking. Here, we explore urea utilization from 50 to 4000 meters depth in the northeastern Pacific Ocean using metagenomics, nitrification rates, and single-cell stable-isotope-uptake measurements with nanoscale secondary ion mass spectrometry. We find that on average 25% of deep-sea cells assimilated urea-derived N (60% of detectably active cells), and that cell-specific nitrogen-incorporation rates from urea were higher than that from ammonium. Both urea concentrations and assimilation rates relative to ammonium generally increased below the euphotic zone. We detected ammonia- and urea-based nitrification at all depths at one of two sites analyzed, demonstrating their potential to support chemoautotrophy in the mesopelagic and bathypelagic regions. Using newly generated metagenomes we find that the ureC gene, encoding the catalytic subunit of urease, is found within 39% of deep-sea cells in this region, including the Nitrososphaeria (syn., Thaumarchaeota; likely for nitrification) as well as members of thirteen other phyla such as Proteobacteria, Verrucomicrobia, Plantomycetota, Nitrospinota, and Chloroflexota (likely for assimilation). Analysis of public metagenomes estimated ureC within 10-46% of deep-sea cells around the world, with higher prevalence below the photic zone, suggesting urea is widely available to the deep-sea microbiome globally. Our results demonstrate that urea is a nitrogen source to abundant and diverse microorganisms in the dark ocean, as well as a significant contributor to deep-sea nitrification and therefore fuel for chemoautotrophy.

Dynamically Confined Active Silver Nanoclusters with Ultrawide Operating Temperature Window in CO oxidation.

Supported metal nanoclusters are often highly active in many catalytic reactions but less stable particularly under harsh reaction conditions. Here, we demonstrate that this activity-stability trade-off can be efficiently broken through rational design of surrounding microenvironment of the supported nanocatalyst including gas adsorbate overlayer and underneath support surface chemistry. Our studies reveal that chemisorbed oxygen species on Ag surface and surface hydroxyl groups on oxide support, which are dynamically consumed during reaction but sustained by reaction environment (O2 and H2O vapor), drive spontaneous redispersion of Ag particles and stabilization of highly active Ag nanoclusters. Such a dynamic confinement effect from gas-catalyst-support interaction enables the Ag nanoclusters to exhibit complete catalytic oxidation of CO over a wide temperature window of 25 - 500 °C under dry conditions and 200 - 800 °C under wet conditions as well as remarkable stability at 300 °C over 1000 h.

Dynamically Confined Active Silver Nanoclusters with Ultrawide Operating Temperature Window in CO oxidation

AbstractSupported metal nanoclusters are often highly active in many catalytic reactions but less stable particularly under harsh reaction conditions. Here, we demonstrate that this activity‐stability trade‐off can be efficiently broken through rational design of surrounding microenvironment of the supported nanocatalyst including gas adsorbate overlayer and underneath support surface chemistry. Our studies reveal that chemisorbed oxygen species on Ag surface and surface hydroxyl groups on oxide support, which are dynamically consumed during reaction but sustained by reaction environment (O2 and H2O vapor), drive spontaneous redispersion of Ag particles and stabilization of highly active Ag nanoclusters. Such a dynamic confinement effect from gas‐catalyst‐support interaction enables the Ag nanoclusters to exhibit complete catalytic oxidation of CO over a wide temperature window of 25‐500 °C under dry conditions and 200‐800 °C under wet conditions as well as remarkable stability at 300 °C over 1000 h.

DBD plasma induced SMOSI and encapsulation for regulation of Brønsted-Lewis acid sites of Cr-MOFs@ZrO2

Dielectric barrier discharge (DBD) plasma for the synthesis of Zr-MOFs followed by the calcination and combination with Cr-MOFs was presented to prepare a Brønsted-Lewis bifunctional catalyst for the conversion of glucose to 5-hydroxymethylfurfural (HMF). The strong electric field on the catalyst surface formed by DBD plasma induced the enhancement of strong metal oxide support interaction (SMOSI), which could be indicated by XPS. SMOSI could change the embedding degree of metal micro-particles. SMOSI accompanied with the encapsulation of Zr metal nanoparticles could regulate the acid sites of the catalysts. Lewis acid played an important role in the isomerization of glucose to fructose, while Brønsted acid played a key role in the further conversion of glucose. The strong Brønsted acid sites determined the conversion of glucose to HMF. Cr-MOFs@ZrO2-D with the DBD plasma method afforded a higher Brønsted to Lewis acid ratio, compared with Cr-MOFs@ZrO2-S with the hydrothermal method. Glucose conversion of 97.9 % and HMF yield of 38 % were obtained with DMF solvent system and Cr-MOFs@ZrO2-D at 150 °C for 2h. This research provided a new method for preparing Zr-MOFs by DBD plasma and a new idea to comprehensively understand the role of Brønsted and Lewis acid sites in glucose conversion.

Engineering Metal‐Support Interaction for Manipulate Microenvironment: Single‐Atom Platinum Decorated on Nickel‐Chromium Oxides Toward High‐Performance Alkaline Hydrogen Evolution

AbstractRational construction of platinum (Pt)‐based single‐atom catalysts (SACs) with high utilization of active sites holds promise to achieve superior electrocatalytic alkaline HER performance, which requires the assistance of functional supports. In this work, a novel catalytic configuration is reported, namely, Pt SACs anchored on the nickel‐chromium oxides labeled as Pt SACs‐NiCrO3/NF. The mechanism associated with the metal‐support interaction (MSI) for synergy co‐catalysis that empowers efficient HER on Pt SACs‐NiCrO3/NF is clarified. Specifically, the modulated electron structure in Pt SACs‐NiCrO3 manipulates the interface microenvironment, mediating a more free water state, which is beneficial to accelerate front water dissociation behavior on the oxide support. Besides, the homogeneously distributed Pt sites with the created near‐acidic state ensure the subsequent fast proton‐involved reaction. All these determine the comprehensively accelerating HER kinetics. Consequently, Pt SACs‐NiCrO3/NF deliverers considerable HER performance, with overpotentials (η10/η100) of 23/122 mV, high mass activity of 382.77 mA mg−1Pt. When serving in an alkaline water‐based anion exchange membrane electrolytic cell (AEMWE), Pt SACs‐NiCrO3/NF also presents excellent performance (100 mA cm−2 at the cell voltage of 1.51 V and stable up to 100 h), confirming its good prospect.

Biomimetic Elastic Single-Atom Protrusions Enhance Ammonia Electrosynthesis.

Electrocatalytic nitrogen (N2) reduction reaction (eNRR) is a promising route for sustainable ammonia (NH3) generation, but the eNRR efficiency is dramatically impeded by the sluggish reaction kinetics. Herein, inspired by the dynamic extension-contraction of sea anemone tentacles in response to environmental changes, we propose a biomimetic elastic Mo single-atom protrusion on vanadium oxide support (pSA Mo/VOH) electrocatalyst featuring a symmetry-breaking Mo site and an elastic Mo-O4 pyramid for efficient eNRR. In-situ spectroscopy and theoretical calculations reveal that the protruding Mo-induced symmetry-breaking structure optimizes the d electron filling of Mo, enhancing the back-donation to the π* antibonding orbital, effectively polarizing the N≡N bond and reducing the barrier from *N2 to *N2H. Notably, the elastic Mo-O4 pyramidal structure of pSA Mo provides a dynamic Mo-O microenvironment during continuous eNRR processes. This optimizes the electronic structure of the Mo sites based on different reaction intermediates, enhancing the adsorption of various N intermediates and maintaining low barriers throughout the six-step hydrogenation process. Consequently, the elastic pSA Mo/VOH exhibits an excellent NH3 yield rate of 50.71 ± 1.12 μg h-1 mg-1 and a Faradaic efficiency of 35.38 ± 1.03%, outperforming most electrocatalysts.

Insights into the oxygen vacancies in titanium-aluminum composite oxides for Ru-catalyzed bio-oil upgrading using guaiacol as a model compound

The high quality liquid products obtained from upgrading of bio-oil through hydrogenation can serve as viable alternatives to fossil fuels, thereby alleviating the strain on energy supply. In this study, a series of titanium-aluminum composite oxides (TixAlyO) was prepared by a sol-gel method and used as supports to fabricate ruthenium (Ru)-based catalysts for the hydrogenolysis upgrading of bio-oil. Various techniques, including in situ pyridine adsorption-Fourier-transform infrared spectroscopy (in situ Py-FTIR), in situ CO diffuse-reflectance Fourier-transform infrared spectroscopy (in situ CO DRIFTS), and CO2 temperature-programmed desorption (CO2-TPD), were employed to characterize the physicochemical and electronic structures of the catalysts. Using guaiacol as a model compound for bio-oil, the compositions and structures of the TixAlyO supports, as well as the effect of calcination treatment of the supports in an N2 atmosphere, on the hydrogenolysis reactivity, were investigated in detail. The results indicated that the hydrogenolysis rate of Caromatic−O bonds showed a significant linear correlation with the oxygen vacancy/Lewis acid content. Furthermore, the presence of oxygen vacancies facilitated the formation of small Ru nanoparticles. Importantly, calcination of the support in an N2 atmosphere facilitated the formation of metal/oxide interface sites in the Ru/Ti5Al5O-N catalyst, further augmenting its Lewis acidity and reducing the activation energy for the hydrogenolysis of the Caromatic−O bonds. The hydrogenolysis rate of the Caromatic−O bond in guaiacol over the oxygen vacancy-rich catalyst Ru/Ti5Al5O-N was increased by a factor of 2–4 compared to those over Ru-based catalysts with a single oxide support. This study exemplified a novel strategy of oxygen vacancy-promoted hydrogenolysis upgrading of bio-oil.

Biomimetic Elastic Single‐Atom Protrusions Enhance Ammonia Electrosynthesis

Electrocatalytic nitrogen (N2) reduction reaction (eNRR) is a promising route for sustainable ammonia (NH3) generation, but the eNRR efficiency is dramatically impeded by the sluggish reaction kinetics. Herein, inspired by the dynamic extension‐contraction of sea anemone tentacles in response to environmental changes, we propose a biomimetic elastic Mo single‐atom protrusion on vanadium oxide support (pSA Mo/VOH) electrocatalyst featuring a symmetry‐breaking Mo site and an elastic Mo−O4 pyramid for efficient eNRR. In‐situ spectroscopy and theoretical calculations reveal that the protruding Mo‐induced symmetry‐breaking structure optimizes the d electron filling of Mo, enhancing the back‐donation to the π* antibonding orbital, effectively polarizing the N≡N bond and reducing the barrier from *N2 to *N2H. Notably, the elastic Mo−O4 pyramidal structure of pSA Mo provides a dynamic Mo−O microenvironment during continuous eNRR processes. This optimizes the electronic structure of the Mo sites based on different reaction intermediates, enhancing the adsorption of various N intermediates and maintaining low barriers throughout the six‐step hydrogenation process. Consequently, the elastic pSA Mo/VOH exhibits an excellent NH3 yield rate of 50.71 ± 1.12 μg h−1 mg−1 and a Faradaic efficiency of 35.38 ± 1.03%, outperforming most electrocatalysts.

Exploring Pt-Cu synergistic effects on porous SiO2 support with different Pt loadings for low-temperature oxidation of CO and C3H6

To address the high cost of noble metals, this study aims to optimize Pt loading and the synergistic effect of Cu on porous SiO2 support for low-temperature oxidation of CO and C3H6. A simulated test bench system was used to evaluate the performance of PtxCu1/SiO2 (where x= 0.3, 0.5, 0.7, and 1 wt%), Cu1/SiO2 and Ptx/SiO2 (where x= 0.5 and 1 wt%) catalysts with varying Pt loadings. Comprehensive characterization, including BET, XRD, SEM, TEM, and XPS was conducted to assess particle size, structure, and surface morphology. The effects of Pt incorporation on reduction and oxidation properties were further examined using H2-TPR and CO-TPD techniques. Results demonstrated a significant enhancement in catalytic activity with the addition of Cu confirming a synergistic interaction between Pt and Cu. This synergy was particularly pronounced in lower Pt loadings, where PtxCu1/SiO2 composites outperformed Ptx/SiO2 in catalytic activity. Pt addition reduced the particle size, which resulted in the creation of PtCu alloy, with 1 and 0.7 % wt Pt loading exhibiting comparable effects in CO conversion and 0.7 % Pt loading exhibiting better activity at higher temperatures in C3H6 oxidation indicating that catalytic activity was maintained even with a reduced Pt loading. Additionally, minimal difference in activity for C3H6 oxidation was observed among PtxCu1/SiO2 catalysts with 0.7, 0.5, and 0.3 wt% Pt loadings as indicated by T50 and T80 values. Reducing Pt loading from 0.7 wt% had minimal impact on catalytic efficiency for C3H6 oxidation with catalysts maintaining high activity. 0.7 wt% Pt loadings provide sufficient active sites for effective CO and HC oxidation. The enhanced catalytic activity and stability of bimetallic catalysts over monometallic Cu/SiO2 and Pt/SiO2 result from the simultaneous presence of active sites created by the synergetic effect of PtCu alloy formation with optimal ratio and well-optimized surface. These findings demonstrate the potential to optimize Pt usage without compromising catalytic performance, offering a cost-effective approach to catalyst design.

Strong Metal-Support Interaction between Pt and TiO2 over High-temperature CO2 Hydrogenation.

The catalytic activities and stability of oxide-supported metal catalysts are significantly affected by metal-support interactions (MSI) between oxidic supports and supported metals. The surface properties of the support, such as its phase and defects, are crucial in MSI, including both the strong metal-support interaction (SMSI) and electronic metal-support interaction (EMSI). In this study, modulation of SMSI was achieved on rutile-supported Pt nanoparticles (NP) over high-temperature CO2 hydrogenation. The encapsulation of Pt NP surfaces with TiO2-x overlayers is precisely controlled by the defects. It is found that oxygen vacancy defects significantly enhance the catalytic stability of Pt/rutile under high-temperature reverse water-gas shift (RWGS) reaction by inhibiting the occurrence of SMSI. Pt/rutile with oxygen vacancies achieves a 301 molCO×gM-1×h-1 space time yield and considerably catalytic stability (decreased by 8%) at 800 °C over 100 h time-on-stream. Density functional theory (DFT) calculations suggest that the adsorption capacity of Pt NP on the rutile overlayer can be reduced by increasing electron density. Experimental results combined with DFT calculations show that electron transfer from Pt NP to rutile is reduced by the oxygen vacancy defects on Pt/R, preserving the metallic nature of Pt species during CO2 hydrogenation, thereby preventing the formation of SMSI.

Strong Metal‐Support Interaction between Pt and TiO2 over High‐temperature CO2 Hydrogenation

The catalytic activities and stability of oxide‐supported metal catalysts are significantly affected by metal‐support interactions (MSI) between oxidic supports and supported metals. The surface properties of the support, such as its phase and defects, are crucial in MSI, including both the strong metal‐support interaction (SMSI) and electronic metal‐support interaction (EMSI). In this study, modulation of SMSI was achieved on rutile‐supported Pt nanoparticles (NP) over high‐temperature CO2 hydrogenation. The encapsulation of Pt NP surfaces with TiO2−x overlayers is precisely controlled by the defects. It is found that oxygen vacancy defects significantly enhance the catalytic stability of Pt/rutile under high‐temperature reverse water‐gas shift (RWGS) reaction by inhibiting the occurrence of SMSI. Pt/rutile with oxygen vacancies achieves a 301 molCO×gM‐1×h‐1 space time yield and considerably catalytic stability (decreased by 8%) at 800 °C over 100 h time‐on‐stream. Density functional theory (DFT) calculations suggest that the adsorption capacity of Pt NP on the rutile overlayer can be reduced by increasing electron density. Experimental results combined with DFT calculations show that electron transfer from Pt NP to rutile is reduced by the oxygen vacancy defects on Pt/R, preserving the metallic nature of Pt species during CO2 hydrogenation, thereby preventing the formation of SMSI.

Upside-Down Adsorption: The Counterintuitive Influences of Surface Entropy and Surface Hydroxyl Density on Hydrogen Spillover.

Although hydrogen spillover is often invoked to explain anomalies in catalysis, spillover remains a poorly understood phenomenon. Hydrogen spillover (H*) is best described as highly mobile H atom equivalents that arise when H2 migrates from a metal nanoparticle to an oxide or carbon support. In the 60 years since its discovery, few methods have become available to quantify or characterize H*-support interactions. We recently showed in situ infrared spectroscopy and volumetric chemisorption can quantify reversible H2 adsorption on Au/TiO2 catalysts, where adsorbed hydrogen exists as H* and interacts with titania surface hydroxyl (TiOH) groups. Here, we report parallel thermogravimetric analysis and Fourier transform infrared spectroscopy methods for systematically manipulating the surface TiOH density. We examine the role of surface hydroxylation on spillover thermodynamics using van't Hoff studies to determine apparent adsorption enthalpies and entropies at constant H* coverage, which is necessary to maintain constant H* translational entropy. Although surface TiOH groups are the likely adsorption sites, the data show removing hydroxyl groups increases spillover. This surprising finding─that adsorption increases as the adsorption site density decreases─is associated with improved thermodynamics on dehydroxylated surfaces. A strong adsorption enthalpy-entropy correlation implicates the changing surface entropy of the titania support itself (i.e., an initial state effect) is deeply intertwined with the H* configurational entropy. These effects are surprising and should apply to all low-coverage adsorbates where entropy terms dominate more traditional enthalpic considerations. Moreover, this study points toward a kinetic test for invoking spillover in a reaction mechanism: namely, in situ dehydroxylation should enhance spillover processes.

Effect of nickle on cerium oxide support to develop cyclic catalytic methane decomposition followed by CO2 gasification

Catalytic methane decomposition (CMD) offers an eco-friendly method to produce COx-free hydrogen and solid carbon. An innovative approach for catalyst regeneration involves utilizing CO2 as a reactant to produce CO via the Reverse Boudouard Reaction, which serves as a valuable feedstock for various chemicals and fuels. This study aims to investigate the role and interaction of Ni nanoparticles on cerium oxide support by comparing two catalysts: one synthesized via the conventional impregnation method (Imp) and the other through solution combustion synthesis (SCS). Both catalysts containing the same Ni loading of 5 wt% and were tested under identical conditions. Comprehensive characterization techniques, including XRD, H2 and O2 TPR, TEM, SEM, XPS, and Raman spectroscopy, were employed to elucidate the observed performances. The SCS catalyst resulted in smaller Ni nanoparticles with stronger metal-support interaction. Observations revealed both tip and base carbon growth for the SCS catalyst, whereas the Imp catalyst predominantly characterized by tip growth. For the SCS catalyst, carbon nanofibers and nanotubes were observed, and both appeared active in carbon CO2 gasification. For the Imp catalyst, more crystalline carbon is observed. The amount of carbon produced was much more and managed to cover the entire catalyst. For SCS carbon coverage was partial. Two rates of CO2 gasification were observed depending on the extent of carbon coverage. Across all tested temperatures and space velocities, the catalyst prepared by impregnation exhibited higher reaction rates. The Imp catalyst demonstrated 15 % higher CMD and 29 % more generated carbon than SCS. This work demonstrated the critical role of key factors influencing the catalytic performance of this cyclic process. This includes the Ni nanoparticle size and distribution, the metal-support interaction's strength, and the graphitic carbon's nature.