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Highly Stable Self-Cleaning Paints Based on Waste-Valorized PNC-Doped TiO 2 Nanoparticles. ACS Catal 2024; 14:4820-4834. [PMID: 38601782 PMCID: PMC11003396 DOI: 10.1021/acscatal.3c06203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2023] [Revised: 02/14/2024] [Accepted: 02/14/2024] [Indexed: 04/12/2024]
Abstract
Adding photocatalytically active TiO2 nanoparticles (NPs) to polymeric paints is a feasible route toward self-cleaning coatings. While paint modification by TiO2-NPs may improve photoactivity, it may also cause polymer degradation and release of toxic volatile organic compounds. To counterbalance adverse effects, a synthesis method for nonmetal (P, N, and C)-doped TiO2-NPs is introduced, based purely on waste valorization. PNC-doped TiO2-NP characterization by vibrational and photoelectron spectroscopy, electron microscopy, diffraction, and thermal analysis suggests that TiO2-NPs were modified with phosphate (P=O), imine species (R=N-R), and carbon, which also hindered the anatase/rutile phase transformation, even upon 700 °C calcination. When added to water-based paints, PNC-doped TiO2-NPs achieved 96% removal of surface-adsorbed pollutants under natural sunlight or UV, paralleled by stability of the paint formulation, as confirmed by micro-Fourier transform infrared (FTIR) surface analysis. The origin of the photoinduced self-cleaning properties was rationalized by three-dimensional (3D) and synchronous photoluminescence spectroscopy, indicating that the dopants led to 7.3 times stronger inhibition of photoinduced e-/h+ recombination when compared to a benchmark P25 photocatalyst.
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2
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A milder reaction to feed the world. Science 2024; 383:1295. [PMID: 38513044 DOI: 10.1126/science.ado4095] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/23/2024]
Abstract
Surface science defies the complexity of ammonia synthesis.
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3
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Potassium Permanganate-Impregnated Amorphous Silica-Alumina Derived from Sugar Cane Bagasse Ash as an Ethylene Scavenger for Extending Shelf Life of Mango Fruits. ACS OMEGA 2024; 9:6749-6760. [PMID: 38371817 PMCID: PMC10870304 DOI: 10.1021/acsomega.3c08119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Revised: 01/18/2024] [Accepted: 01/24/2024] [Indexed: 02/20/2024]
Abstract
Ethylene, a plant hormone, is a gas that plays a crucial role in fruit ripening and senescence. In this work, a novel ethylene scavenger was prepared from amorphous silica-alumina derived from sugar cane bagasse ash (SC-ASA) and used to prolong the shelf life of mango fruits during storage. KMnO4 at 2, 4, or 6 wt %/w was loaded on SC-ASA using an impregnation method. The results showed that 4% w/w KMnO4 loaded on SC-ASA (4KM/SC-ASA) was superior for ethylene removal at an initial ethylene concentration of 400 μL L-1 for 120 min under ambient conditions (25-27 °C and 70-75% relative humidity), resulting in 100% ethylene removal. The kinetic study of ethylene removal showed that the adsorption data were best fitted with a pseudo-first-order kinetic model. The effects of 4KM/SC-ASA as sachets on the quality changes of the mango fruits were investigated, with the results showing that mango fruits packed in cardboard boxes with 4KM/SC-ASA had significantly delayed ripening, low levels of ethylene production, respiration, and weight loss, high fruit firmness, low total soluble solids, and high acidity compared to those of the control treatment. These findings should contribute to developing an ethylene scavenger to extend the shelf life of fruits, reduce the waste of the sugar and ethanol industries, and make it a valuable material.
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4
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Microalgae-derived Co 3O 4 nanomaterials for catalytic CO oxidation. RSC Adv 2024; 14:4575-4586. [PMID: 38318608 PMCID: PMC10839636 DOI: 10.1039/d4ra00343h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2024] [Accepted: 01/30/2024] [Indexed: 02/07/2024] Open
Abstract
Efficient carbon monoxide oxidation is important to reduce its impacts on both human health and the environment. Following a sustainable synthesis route toward new catalysts, nanosized Co3O4 was synthesized based on extracts of microalgae: Spirulina platensis, Chlorella vulgaris, and Haematococcus pluvialis. Using the metabolites in the extract and applying different calcination temperatures (450, 650, 800 °C) led to Co3O4 catalysts with distinctly different properties. The obtained Co3O4 nanomaterials exhibited octahedral, nanosheet, and spherical morphologies with structural defects and surface segregation of phosphorous and potassium, originating from the extracts. The presence of P and K in the oxide nanostructures significantly improved their catalytic CO oxidation activity. When normalized by the specific surface area, the microalgae-derived catalysts exceeded a commercial benchmark catalyst. In situ studies revealed differences in oxygen mobility and carbonate formation during the reaction. The obtained insights may facilitate the development of new synthesis strategies for manufacturing highly active Co3O4 nanocatalysts.
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5
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Lanthanum modulated reaction pacemakers on a single catalytic nanoparticle. Nat Commun 2023; 14:7186. [PMID: 37938552 PMCID: PMC10632447 DOI: 10.1038/s41467-023-43026-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Accepted: 10/30/2023] [Indexed: 11/09/2023] Open
Abstract
Promoters are important in catalysis, but the atomistic details of their function and particularly their role in reaction instabilities such as kinetic phase transitions and oscillations are often unknown. Employing hydrogen oxidation as probe reaction, a Rh nanotip for mimicking a single Rh nanoparticle and field electron microscopy for in situ monitoring, we demonstrate a La-mediated local catalytic effect. The oscillatory mode of the reaction provides a tool for studying the interplay between different types of reaction pacemakers, i.e., specific local surface atomic configurations that initiate kinetic transitions. The presence of La shifts the bistable reaction states, changes the oscillation pattern and deactivates one of two pacemaker types for the La-free surface. The observed effects originate from the La-enhanced oxygen activation on the catalyst. The experimental observations are corroborated by micro-kinetic model simulations comprising a system of 25 coupled oscillators.
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Directing Intrinsic Chirality in Gold Nanoclusters: Preferential Formation of Stable Enantiopure Clusters in High Yield and Experimentally Unveiling the "Super" Chirality of Au 144. ACS NANO 2023; 17:20376-20386. [PMID: 37805942 PMCID: PMC10604085 DOI: 10.1021/acsnano.3c06568] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Accepted: 09/28/2023] [Indexed: 10/10/2023]
Abstract
Chiral gold nanoclusters offer significant potential for exploring chirality at a fundamental level and for exploiting their applications in sensing and catalysis. However, their widespread use is impeded by low yields in synthesis, tedious separation procedures of their enantiomeric forms, and limited thermal stability. In this study, we investigated the direct synthesis of enantiopure chiral nanoclusters using the chiral ligand 2-MeBuSH in the fabrication of Au25, Au38, and Au144 nanoclusters. Notably, this approach leads to the unexpected formation of intrinsically chiral clusters with high yields for chiral Au38 and Au144 nanoclusters. Experimental evaluation of chiral activity by circular dichroism (CD) spectroscopy corroborates previous theoretical calculations, highlighting the stronger CD signal exhibited by Au144 compared to Au38 or Au25. Furthermore, the formation of a single enantiomeric form is experimentally confirmed by comparing it with intrinsically chiral Au38(2-PET)24 (2-PET: 2-phenylethanethiol) and is supported theoretically for both Au38 and Au144. Moreover, the prepared chiral clusters show stability against diastereoisomerization, up to temperatures of 80 °C. Thus, our findings not only demonstrate the selective preparation of enantiopure, intrinsically chiral, and highly stable thiolate-protected Au nanoclusters through careful ligand design but also support the predicted "super" chirality in the Au144 cluster, encompassing hierarchical chirality in ligands, staple configuration, and core structure.
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Highly Efficient Conversion of Greenhouse Gases Using a Quadruple Mixed Oxide-Supported Nickel Catalyst in Reforming Process. Ind Eng Chem Res 2023; 62:16254-16267. [PMID: 37841414 PMCID: PMC10571087 DOI: 10.1021/acs.iecr.3c02030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Revised: 09/13/2023] [Accepted: 09/14/2023] [Indexed: 10/17/2023]
Abstract
The greenhouse gas reduction as well as the utilization of more renewable and clean energy via a dry reforming reaction is of interest. The impact of a CeMgZnAl oxide quad-blend-supported Ni catalyst on performance and anticoking during dry reforming reactions at 700 °C was studied. A high Ce-Mg/Zn ratio, as seen in the CeMg0.5ZnAl-supported nickel catalyst, enhances lattice oxygen, and the presence of strong basic sites, along with the creation of the carbonate intermediate species, is accompanied by the production of gaseous CO through a gasification reaction between the carbon species and Ni-COads-lin site. The phenomena caused the outstanding performance of the Ni/CeMg0.5ZnAl catalyst-CH4 (84%),CO2 (83%) conversions, and the H2/CO (0.80) ratio; moreover, its activity was also stable throughout 30 h.
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Kinetic and Computational Studies of CO Oxidation and PROX on Cu/CeO 2 Nanospheres. Top Catal 2023; 66:1129-1142. [PMID: 37724312 PMCID: PMC10505120 DOI: 10.1007/s11244-023-01848-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/01/2023] [Indexed: 09/20/2023]
Abstract
As supported CuO is well-known for low temperature activity, CuO/CeO2 nanosphere catalysts were synthesized and tested for CO oxidation and preferential oxidation of CO (PROX) in excess H2. For the first reaction, ignition was observed at 95 °C, whereas selective PROX occurred in a temperature window from 50 to 100 °C. The catalytic performance was independent of the initial oxidation state of the catalyst (CuO vs. Cu0), suggesting that the same active phase is formed under reaction conditions. Density functional modeling was applied to elucidate the intermediate steps of CO oxidation, as well as those of the comparably less feasible H2 transformation. In the simulations, various Cu and vacancy sites were probed as reactive centers enabling specific pathways. Supplementary Information The online version contains supplementary material available at 10.1007/s11244-023-01848-x.
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Imaging Interface and Particle Size Effects by In Situ Correlative Microscopy of a Catalytic Reaction. ACS Catal 2023; 13:7650-7660. [PMID: 37288091 PMCID: PMC10242684 DOI: 10.1021/acscatal.3c00060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Revised: 03/17/2023] [Indexed: 06/09/2023]
Abstract
The catalytic behavior of Rh particles supported by three different materials (Rh, Au, and ZrO2) in H2 oxidation has been studied in situ by correlative photoemission electron microscopy (PEEM) and scanning photoemission electron microscopy (SPEM). Kinetic transitions between the inactive and active steady states were monitored, and self-sustaining oscillations on supported Rh particles were observed. Catalytic performance differed depending on the support and Rh particle size. Oscillations varied from particle size-independent (Rh/Rh) via size-dependent (Rh/ZrO2) to fully inhibited (Rh/Au). For Rh/Au, the formation of a surface alloy induced such effects, whereas for Rh/ZrO2, the formation of substoichiometric Zr oxides on the Rh surface, enhanced oxygen bonding, Rh-oxidation, and hydrogen spillover onto the ZrO2 support were held responsible. The experimental observations were complemented by micro-kinetic simulations, based on variations of hydrogen adsorption and oxygen binding. The results demonstrate how correlative in situ surface microscopy enables linking of the local structure, composition, and catalytic performance.
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10
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Partial Oxidation of Bio-methane over Nickel Supported on MgO-ZrO 2 Solid Solutions. Top Catal 2023; 66:1539-1552. [PMID: 37830054 PMCID: PMC10564672 DOI: 10.1007/s11244-023-01822-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/19/2023] [Indexed: 10/14/2023]
Abstract
Syngas can be produced from biomethane via Partial Oxidation of Methane (POM), being an attractive route since it is ecofriendly and sustainable. In this work, catalysts of Ni supported on MgO-ZrO2 solid solutions, prepared by a one-step polymerization method, were characterized by HRTEM/EDX, XRD, XPS, H2-TPR, and in situ XRD. All catalysts, including Ni/ZrO2 and Ni/MgO as reference, were tested for POM (CH4:O2 molar ratio 2, 750 ºC, 1 atm). NiO/MgO/ZrO2 contained two solid-solutions, MgO-ZrO2 and NiO-MgO, as revealed by XRD and XPS. Ni (30 wt%) supported on MgO-ZrO2 solid solution exhibited high methane conversion and hydrogen selectivity. However, depending on the MgO amount (0, 4, 20, 40, 100 molar percent) major differences in NiO reducibility, growth of Ni0 crystallite size during H2 reduction and POM, and in carbon deposition rates were observed. Interestingly, catalysts with lower MgO content achieved the highest CH4 conversion (~ 95%), high selectivity to H2 (1.7) and CO (0.8), and low carbon deposition rates (0.024 g carbon.gcat-1 h-1) with Ni4MgZr (4 mol% MgO) turning out to be the best catalyst. In situ XRD during POM indicated metallic Ni nanoparticles (average crystallite size of 31 nm), supported by MgO-ZrO2 solid solution, with small amounts of NiO-MgO being present as well. The presence of MgO also influenced the morphology of the carbon deposits, leading to filaments instead of amorphous carbon. A combustion-reforming mechanism is suggested and using a MgO-ZrO2 solid solution support strongly improves catalytic performance, which is attributed to effective O2, CO2 and H2O activation at the Ni/MgO-ZrO2 interface.
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11
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Pineapple-Leaf-Derived, Copper-PAN-Modified Regenerated Cellulose Sheet Used as a Hydrogen Sulfide Indicator. ACS OMEGA 2023; 8:17134-17142. [PMID: 37214707 PMCID: PMC10193420 DOI: 10.1021/acsomega.3c01449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Accepted: 04/24/2023] [Indexed: 05/24/2023]
Abstract
Regenerated cellulose (RC) produced from waste pineapple leaves was used to develop a colorimetric sensor as a Cu-PAN sheet (RCS). Microcrystalline cellulose derived from dried pineapple leaves was combined with Cu-PAN, dissolved in NaOH and urea, and made into an RC sheet using Na2SO4 as a coagulant. The RCS was used as an H2S indicator at various H2S concentrations (0-50 ppm) and temperatures (5-25 °C). The RCS color changed from purple to New York pink when exposed to H2S. A colorimeter method was used to develop prediction curves with values of R2 > 0.95 for H2S concentrations at 5-25 °C. The physicochemical properties of fresh and spent RCS were characterized using various techniques (Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy/energy-dispersive X-ray spectroscopy, and thermogravimetric analysis). In addition, when stored at 5 and 25 °C for 90 days, the RCS had outstanding stability. The developed RCS could be applied to food packaging as an intelligent indicator of meat spoilage.
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Polarisationsabhängige Summenfrequenzspektroskopie (SFG) zur in situ Bestimmung der Nanopartikel-Morphologie. ANGEWANDTE CHEMIE (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023; 135:e202300230. [PMID: 38516007 PMCID: PMC10952846 DOI: 10.1002/ange.202300230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Indexed: 03/23/2024]
Abstract
AbstractDie Oberflächenstruktur von Metall‐Nanopartikel auf Oxidträgern lässt sich über charakteristische Schwingungen von adsorbierten Sondenmolekülen wie CO bestimmen. Üblicherweise konzentrieren sich spektroskopische Untersuchungen auf die Peak‐Position und ‐Intensität, die mit der Bindungsgeometrie bzw. der Anzahl der Adsorptionsplätze zusammenhängen. Anhand zweier unterschiedlich präparierter Modellkatalysatoren wird gezeigt, dass die polarisationsabhängige Summenfrequenzspektroskopie (SFG) die gemittelte Oberflächenstruktur und Form von Nanopartikel beleuchten kann. SFG‐Ergebnisse für verschiedene Partikelgrößen und Morphologien werden mit direkter Realraum‐Strukturanalyse mittels TEM und STM verglichen. Die beschriebene Anwendung von SFG kann zur in situ Detektion der Partikelstruktur verwendet werden und könnte ein wertvolles Werkzeug in der operando Katalyse werden.
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Polarization-Dependent Sum-Frequency-Generation Spectroscopy for In Situ Tracking of Nanoparticle Morphology. Angew Chem Int Ed Engl 2023; 62:e202300230. [PMID: 36883879 PMCID: PMC10947018 DOI: 10.1002/anie.202300230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Revised: 03/07/2023] [Accepted: 03/08/2023] [Indexed: 03/09/2023]
Abstract
The surface structure of oxide-supported metal nanoparticles can be determined via characteristic vibrations of adsorbed probe molecules such as CO. Usually, spectroscopic studies focus on peak position and intensity, which are related to binding geometries and number of adsorption sites, respectively. Employing two differently prepared model catalysts, it is demonstrated that polarization-dependent sum-frequency-generation (SFG) spectroscopy reveals the average surface structure and shape of the nanoparticles. SFG results for different particle sizes and morphologies are compared to direct real-space structure analysis by TEM and STM. The described feature of SFG could be used to monitor particle restructuring in situ and may be a valuable tool for operando catalysis.
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14
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Formation of Periodic Surface Structures by Multipulse Femtosecond Laser Processing of Au-Coated Ni in Various Fluids. ACS APPLIED ENGINEERING MATERIALS 2023; 1:1263-1276. [PMID: 37152716 PMCID: PMC10152447 DOI: 10.1021/acsaenm.3c00070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/19/2023] [Accepted: 03/23/2023] [Indexed: 05/09/2023]
Abstract
Using multipulse linearly polarized femtosecond laser processing of a Au-coated Ni surface in various liquid media created subwavelength self-organized nanoripples. The thin gold film improved the laser absorptivity, decreasing the ripple generation threshold in liquids. High spatial frequency ripples exhibited lower angular deviation than low spatial frequency ones, but in water the deviation was comparable for both types of ripples. The initiation of nanoripples may precede nanoparticle generation, which is why in hexane several cuboid Au particles were trapped between the ripples. Fast cooling processes freeze ejected molten droplets during the phase explosion and surface reorganization. Grazing incidence X-ray diffraction of samples processed in butanol showed a small shift toward smaller angles for the Ni phase, indicating a lattice expansion due to higher tensile stress. Confocal micro-Raman spectroscopy detected surface graphitization and amorphization in areas laser-treated in ethanol, butanol, and hexane, with the highest carbonization observed in butanol. Presumably, femtosecond laser-induced photolysis triggers the formation of graphite nanocrystallites, and consecutive pulses cause amorphization. Static contact angle measurements showed a general tendency toward hydrophobicity with highest contact angles for rippled areas created in butanol.
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Conversion of Methane to Value-Added Hydrocarbons via Modified Fischer–Tropsch Process Using Hybrid Catalysts. Top Catal 2023. [DOI: 10.1007/s11244-023-01808-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/03/2023]
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Emergence of chaos in a compartmentalized catalytic reaction nanosystem. Nat Commun 2023; 14:736. [PMID: 36759520 PMCID: PMC9911747 DOI: 10.1038/s41467-023-36434-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Accepted: 02/01/2023] [Indexed: 02/11/2023] Open
Abstract
In compartmentalized systems, chemical reactions may proceed in differing ways even in adjacent compartments. In compartmentalized nanosystems, the reaction behaviour may deviate from that observed on the macro- or mesoscale. In situ studies of processes in such nanosystems meet severe experimental challenges, often leaving the field to theoretical simulations. Here, a rhodium nanocrystal surface consisting of different nm-sized nanofacets is used as a model of a compartmentalized reaction nanosystem. Using field emission microscopy, different reaction modes are observed, including a transition to spatio-temporal chaos. The transitions between different modes are caused by variations of the hydrogen pressure modifying the strength of diffusive coupling between individual nanofacets. Microkinetic simulations, performed for a network of 52 coupled oscillators, reveal the origins of the different reaction modes. Since diffusive coupling is characteristic for many living and non-living compartmentalized systems, the current findings may be relevant for a wide class of reaction systems.
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Operando monitoring of a room temperature nanocomposite methanol sensor. Catal Sci Technol 2023; 13:624-636. [PMID: 36760342 PMCID: PMC9900598 DOI: 10.1039/d2cy01395a] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Accepted: 12/13/2022] [Indexed: 12/15/2022]
Abstract
The sensing of volatile organic compounds by composites containing metal oxide semiconductors is typically explained via adsorption-desorption and surface electrochemical reactions changing the sensor's resistance. The analysis of molecular processes on chemiresistive gas sensors is often based on indirect evidence, whereas in situ or operando studies monitoring the gas/surface interactions enable a direct insight. Here we report a cross-disciplinary approach employing spectroscopy of working sensors to investigate room temperature methanol detection, contrasting well-characterized nanocomposite (TiO2@rGO-NC) and reduced-graphene oxide (rGO) sensors. Methanol interactions with the sensors were examined by (quasi) operando-DRIFTS and in situ-ATR-FTIR spectroscopy, the first paralleled by simultaneous measurements of resistance. The sensing mechanism was also studied by mass spectroscopy (MS), revealing the surface electrochemical reactions. The operando and in situ spectroscopy techniques demonstrated that the sensing mechanism on the nanocomposite relies on the combined effect of methanol reversible physisorption and irreversible chemisorption, sensor modification over time, and electron/O2 depletion-restoration due to a surface electrochemical reaction forming CO2 and H2O.
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Doped metal clusters as bimetallic AuCo nanocatalysts: insights into structural dynamics and correlation with catalytic activity by in situ spectroscopy. Faraday Discuss 2023; 242:94-105. [PMID: 36330869 PMCID: PMC9890489 DOI: 10.1039/d2fd00120a] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Co-doped Au25 nanoclusters with different numbers of doping atoms were synthesized and supported on CeO2. The catalytic properties were studied in the CO oxidation reaction. In all cases, an enhancement in catalytic activity was observed compared to the pure Au25 nanocluster catalyst. Interestingly, a different catalytic performance was obtained depending on the number of Co atoms within the cluster. This was related to the mobility of atoms within the cluster's structure under pretreatment and reaction conditions, resulting in active CoAu nanoalloy sites. The evolution of the doped Au clusters into nanoalloys with well-distributed Co atoms within the Au cluster structure was revealed by combined XAFS, DRIFTS, and XPS studies. Overall, these studies contribute to a better understanding of the dynamics of doped nanoclusters on supports upon pretreatment and reaction, which is key information for the future development and application of bimetallic nanocluster (nanoalloy) catalysts.
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Direct Conversion of Methane to Value-added Hydrocarbons Using Hybrid Catalysts of Ni/Al2O3 and K-Co/Al2O3. REACT CHEM ENG 2023. [DOI: 10.1039/d3re00055a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/03/2023]
Abstract
The direct conversion of methane (CH4) to value-added hydrocarbons (C2+) was studied using a hybrid catalyst, consisting of Ni/Al2O3 as the first catalyst layer to convert CH4 to carbon monoxide,...
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Mo 2TiC 2 MXene-Supported Ru Clusters for Efficient Photothermal Reverse Water-Gas Shift. ACS NANO 2022; 17:1550-1559. [PMID: 36584240 PMCID: PMC9878975 DOI: 10.1021/acsnano.2c10707] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Accepted: 12/23/2022] [Indexed: 06/17/2023]
Abstract
Driving metal-cluster-catalyzed high-temperature chemical reactions by sunlight holds promise for the development of negative-carbon-footprint industrial catalysis, which has yet often been hindered by the poor ability of metal clusters to harvest and utilize the full spectrum of solar energy. Here, we report the preparation of Mo2TiC2 MXene-supported Ru clusters (Ru/Mo2TiC2) with pronounced broadband sunlight absorption ability and high sintering resistance. Under illumination of focused sunlight, Ru/Mo2TiC2 can catalyze the reverse water-gas shift (RWGS) reaction to produce carbon monoxide from the greenhouse gas carbon dioxide and renewable hydrogen with enhanced activity, selectivity, and stability compared to their nanoparticle counterparts. Notably, the CO production rate of MXene-supported Ru clusters reached 4.0 mol·gRu-1·h-1, which is among the best reported so far for photothermal RWGS catalysts. Detailed studies suggest that the production of methane is kinetically inhibited by the rapid desorption of CO from the surface of the Ru clusters.
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Reaction Modes on a Single Catalytic Particle: Nanoscale Imaging and Micro-Kinetic Modeling. ACS Catal 2022; 12:12774-12785. [PMID: 36313520 PMCID: PMC9594309 DOI: 10.1021/acscatal.2c02901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Revised: 08/04/2022] [Indexed: 11/29/2022]
Abstract
![]()
The kinetic behavior of individual Rh(hkl) nanofacets
coupled in a common reaction system was studied using the apex of
a curved rhodium microcrystal (radius of 0.65 μm) as a model
of a single catalytic particle and field electron microscopy for in
situ imaging of catalytic hydrogen oxidation. Depending on the extent
of interfacet coupling via hydrogen diffusion, different oscillating
reaction modes were observed including highly unusual multifrequential
oscillations: differently oriented nanofacets oscillated with differing
frequencies despite their immediate neighborhood. The transitions
between different modes were induced by variations in the particle
temperature, causing local surface reconstructions, which create locally
protruding atomic rows. These atomic rows modified the coupling strength
between individual nanofacets and caused the transitions between different
oscillating modes. Effects such as entrainment, frequency locking,
and reconstruction-induced collapse of spatial coupling were observed.
To reveal the origin of the different experimentally observed effects,
microkinetic simulations were performed for a network of 105 coupled
oscillators, modeling the individual nanofacets communicating via
hydrogen surface diffusion. The calculated behavior of the oscillators,
the local frequencies, and the varying degree of spatial synchronization
describe the experimental observations well.
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Pattern Formation in Catalytic H 2 Oxidation on Rh: Zooming in by Correlative Microscopy. ACS Catal 2022; 12:11974-11983. [PMID: 36249872 PMCID: PMC9552168 DOI: 10.1021/acscatal.2c03692] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Revised: 08/31/2022] [Indexed: 11/29/2022]
Abstract
![]()
Spatio-temporal nonuniformities in H2 oxidation
on individual
Rh(h k l) domains of a polycrystalline Rh foil were studied in the 10–6 mbar pressure range by photoemission electron microscopy
(PEEM), X-ray photoemission electron microscopy (XPEEM), and low-energy
electron microscopy (LEEM). The latter two were used for in situ correlative
microscopy to zoom in with significantly higher lateral resolution,
allowing detection of an unusual island-mediated oxygen front propagation
during kinetic transitions. The origin of the island-mediated front
propagation was rationalized by model calculations based on a hybrid
approach of microkinetic modeling and Monte Carlo simulations.
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23
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In situ methods: discoveries and challenges: general discussion. Faraday Discuss 2022; 236:219-266. [PMID: 35968885 DOI: 10.1039/d2fd90025d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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24
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Buried interfaces: general discussion. Faraday Discuss 2022; 236:338-351. [PMID: 35920282 DOI: 10.1039/d2fd90026b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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25
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Time resolved surface analysis (kinetic and molecular time scales): general discussion. Faraday Discuss 2022; 236:510-527. [PMID: 35861561 DOI: 10.1039/d2fd90029g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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26
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CeO
2
Supported Gold Nanocluster Catalysts for CO Oxidation: Surface Evolution Influenced by the Ligand Shell. ChemCatChem 2022. [DOI: 10.1002/cctc.202200779] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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27
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Active sites and deactivation of room temperature CO oxidation on Co 3O 4catalysts: combined experimental and computational investigations. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:354001. [PMID: 35588721 DOI: 10.1088/1361-648x/ac718b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Accepted: 05/19/2022] [Indexed: 06/15/2023]
Abstract
Co3O4is a well-known low temperature CO oxidation catalyst, but it often suffers from deactivation. We have thus examined room temperature (RT) CO oxidation on Co3O4catalysts by operando DSC, TGA and MS measurements, as well as by pulsed chemisorption to differentiate the contributions of CO adsorption and reaction to CO2. Catalysts pretreated in oxygen at 400 °C are most active, with the initial interaction of CO and Co3O4being strongly exothermic and with maximum amounts of CO adsorption and reaction. The initially high RT activity then levels-off, suggesting that the oxidative pretreatment creates an oxygen-rich reactive Co3O4surface that upon reaction onset loses its most active oxygen. This specific active oxygen is not reestablished by gas phase O2during the RT reaction. When the reaction temperature is increased to 150 °C, full conversion can be maintained for 100 h, and even after cooling back to RT. Apparently, deactivating species are avoided this way, whereas exposing the active surface even briefly to pure CO leads to immediate deactivation. Computational modeling using DFT helped to identify the CO adsorption sites, determine oxygen vacancy formation energies and the origin of deactivation. A new species of CO bonded to oxygen vacancies at RT was identified, which may block a vacancy site from further reaction unless CO is removed at higher temperature. The interaction between oxygen vacancies was found to be small, so that in the active state several lattice oxygen species are available for reaction in parallel.
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28
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CeO2 Supported Gold Nanocluster Catalysts for CO oxidation: Surface Evolution Influenced by the Ligand Shell. ChemCatChem 2022; 14:e202200322. [PMID: 36035519 PMCID: PMC9400996 DOI: 10.1002/cctc.202200322] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2022] [Revised: 04/07/2022] [Indexed: 11/15/2022]
Abstract
Monolayer protected Au nanocluster catalysts are known to undergo structural changes during catalytic reactions, including dissociation and migration of ligands onto the support, which strongly affects their activity and stability. To better understand how the nature of ligands influences the catalytic activity of such catalysts, three types of ceria supported Au nanoclusters with different kinds of ligands (thiolates, phosphines and a mixture thereof) have been studied, employing CO oxidation as model reaction. The thiolate‐protected Au25/CeO2 showed significantly higher CO conversion after activation at 250 °C than the cluster catalysts possessing phosphine ligands. Temperature programmed oxidation and in situ infrared spectroscopy revealed that while the phosphine ligands seemed to decompose and free Au surface was exposed, temperatures higher than 250 °C are required to efficiently remove them from the whole catalyst system. Moreover, the presence of residues on the support seemed to have much greater influence on the reactivity than the gold particle size.
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29
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CO Adsorption and Disproportionation on Smooth and Defect-Rich Ir(111). THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2022; 126:6578-6589. [PMID: 35493699 PMCID: PMC9036526 DOI: 10.1021/acs.jpcc.2c01141] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Revised: 03/26/2022] [Indexed: 06/14/2023]
Abstract
CO adsorption and dissociation on "perfect" and "defect-rich" Ir(111) surfaces were studied by a combination of surface-analytical techniques, including polarization-dependent (PPP and SSP) sum frequency generation (SFG) vibrational spectroscopy, low-energy electron diffraction (LEED), Auger electron spectroscopy, X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations. CO was found to be ordered and tilted from the surface normal at high coverage on the "perfect" surface (e.g., θ = 30° at 0.70 ML), whereas it was less ordered and preferentially upright (θ = 4-10°) on the "defect-rich" surface for coverages of 0.55-0.70 ML. SFG, LEED, and XPS revealed that CO adsorption at low pressure/high temperature and high pressure/low temperature was reversible. In contrast, upon heating to ∼600 K in near mbar CO pressure, "perfect" and even more "defect-rich" Ir(111) surfaces were irreversibly modified by carbon deposits, which, according to DFT, result from CO disproportionation.
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30
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Gold nanoclusters supported on different materials as catalysts for the selective alkyne semihydrogenation. Catal Today 2022. [DOI: 10.1016/j.cattod.2022.02.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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31
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32
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Effects of Mg, Ca, Sr, and Ba Dopants on the Performance of La 2O 3 Catalysts for the Oxidative Coupling of Methane. ACS OMEGA 2022; 7:1785-1793. [PMID: 35071872 PMCID: PMC8771708 DOI: 10.1021/acsomega.1c04738] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Accepted: 12/22/2021] [Indexed: 06/14/2023]
Abstract
Oxidative coupling of methane (OCM) is a reaction to directly convert methane into high value-added hydrocarbons (C2+) such as ethylene and ethane using molecular oxygen and a catalyst. This work investigated lanthanum oxide catalysts for OCM, which were promoted with alkaline-earth metal oxides (Mg, Ca, Sr, and Ba) and prepared by the solution-mixing method. The synthesized catalysts were characterized using X-ray powder diffraction, CO2-programmed desorption, and X-ray photoelectron spectroscopy. The comparative performance of each promoter showed that promising lanthanum-loaded alkaline-earth metal oxide catalysts were La-Sr and La-Ba. In contrast, the combination of La with Ca or Mg did not lead to a clear improvement of C2+ yield. The most promising LaSr50 catalyst exhibited the highest C2+ yield of 17.2%, with a 56.0% C2+ selectivity and a 30.9% CH4 conversion. Catalyst characterization indicated that their activity was strongly associated with moderate basic sites and surface-adsorbed oxygen species of O2 -. Moreover, the catalyst was stable over 25 h at a reactor temperature of 700 °C.
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33
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Selective ligand removal to improve accessibility of active sites in hierarchical MOFs for heterogeneous photocatalysis. Nat Commun 2022; 13:282. [PMID: 35022390 PMCID: PMC8755752 DOI: 10.1038/s41467-021-27775-7] [Citation(s) in RCA: 33] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Accepted: 12/08/2021] [Indexed: 11/20/2022] Open
Abstract
Metal-organic frameworks (MOFs) are commended as photocatalysts for H2 evolution and CO2 reduction as they combine light-harvesting and catalytic functions with excellent reactant adsorption capabilities. For dynamic processes in liquid phase, the accessibility of active sites becomes a critical parameter as reactant diffusion is limited by the inherently small micropores. Our strategy is to introduce additional mesopores by selectively removing one ligand in mixed-ligand MOFs via thermolysis. Here we report photoactive MOFs of the MIL-125-Ti family with two distinct mesopore architectures resembling either large cavities or branching fractures. The ligand removal is highly selective and follows a 2-step process tunable by temperature and time. The introduction of mesopores and the associated formation of new active sites have improved the HER rates of the MOFs by up to 500%. We envision that this strategy will allow the purposeful engineering of hierarchical MOFs and advance their applicability in environmental and energy technologies.
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34
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Ru-Catalyzed Reverse Water Gas Shift Reaction with Near-Unity Selectivity and Superior Stability. ACS MATERIALS LETTERS 2021; 3:1652-1659. [PMID: 34901871 PMCID: PMC8653414 DOI: 10.1021/acsmaterialslett.1c00523] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Accepted: 10/25/2021] [Indexed: 05/31/2023]
Abstract
Cascade catalysis of reverse water gas shift (RWGS) and well-established CO hydrogenation holds promise for the conversion of greenhouse gas CO2 and renewable H2 into liquid hydrocarbons and methanol under mild conditions. However, it remains a big challenge to develop low-temperature RWGS catalysts with high activity, selectivity, and stability. Here, we report the design of an efficient RWGS catalyst by encapsulating ruthenium clusters with the size of 1 nm inside hollow silica shells. The spatially confined structure prevents the sintering of Ru clusters while the permeable silica layer allows the diffusion of gaseous reactants and products. This catalyst with reduced particle sizes not only inherits the excellent activity of Ru in CO2 hydrogenation reactions but also exhibits nearly 100% CO selectivity and superior stability at 200-500 °C. The ability to selectively produce CO from CO2 at relatively low temperatures paves the way for the production of value-added fuels from CO2 and renewable H2.
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35
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Abstract
In an effort to combine the favorable catalytic properties of Co3 O4 and CeO2 , nanocomposites with different phase distribution and Co3 O4 loading were prepared and employed for CO oxidation. Synthesizing Co3 O4 -modified CeO2 via three different sol-gel based routes, each with 10.4 wt % Co3 O4 loading, yielded three different nanocomposite morphologies: CeO2 -supported Co3 O4 layers, intermixed oxides, and homogeneously dispersed Co. The reactivity of the resulting surface oxygen species towards CO were examined by temperature programmed reduction (CO-TPR) and flow reactor kinetic tests. The first morphology exhibited the best performance due to its active Co3 O4 surface layer, reducing the light-off temperature of CeO2 by about 200 °C. In contrast, intermixed oxides and Co-doped CeO2 suffered from lower dispersion and organic residues, respectively. The performance of Co3 O4 -CeO2 nanocomposites was optimized by varying the Co3 O4 loading, characterized by X-ray diffraction (XRD) and N2 sorption (BET). The 16-65 wt % Co3 O4 -CeO2 catalysts approached the conversion of 1 wt % Pt/CeO2 , rendering them interesting candidates for low-temperature CO oxidation.
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36
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Coexisting multi-states in catalytic hydrogen oxidation on rhodium. Nat Commun 2021; 12:6517. [PMID: 34764290 PMCID: PMC8586342 DOI: 10.1038/s41467-021-26855-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Accepted: 10/18/2021] [Indexed: 11/23/2022] Open
Abstract
Catalytic hydrogen oxidation on a polycrystalline rhodium foil used as a surface structure library is studied by scanning photoelectron microscopy (SPEM) in the 10-6 mbar pressure range, yielding spatially resolved X-ray photoemission spectroscopy (XPS) measurements. Here we report an observation of a previously unknown coexistence of four different states on adjacent differently oriented domains of the same Rh sample at the exactly same conditions. A catalytically active steady state, a catalytically inactive steady state and multifrequential oscillating states are simultaneously observed. Our results thus demonstrate the general possibility of multi-states in a catalytic reaction. This highly unusual behaviour is explained on the basis of peculiarities of the formation and depletion of subsurface oxygen on differently structured Rh surfaces. The experimental findings are supported by mean-field micro-kinetic modelling. The present observations raise the interdisciplinary question of how self-organising dynamic processes in a heterogeneous system are influenced by the permeability of the borders confining the adjacent regions.
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37
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Abstract
Replacement of protecting ligands of gold nanoclusters by ligand exchange has become an established post-synthetic tool for selectively modifying the nanoclusters' properties. Several Au nanoclusters are known to additionally undergo size transformations upon ligand exchange, enabling access to cluster structures that are difficult to obtain by direct synthesis. This work reports on the selective size transformation of Au15(SG)13 (SG: glutathione) nanoclusters to Au16(2-PET)14 (2-PET: 2-phenylethanethiol) nanoclusters through a two-phase ligand exchange process at room temperature. Among several parameters evaluated, the addition of a large excess of exchange thiol (2-PET) to the organic phase was identified as the key factor for the structure conversion. After exchange, the nature of the clusters was determined by UV-vis, electrospray ionization-time of flight mass spectrometry, attenuated total reflection-Fourier transform infrared, and extended x-ray absorption fine-structure spectroscopy. The obtained Au16(2-PET)14 clusters proved to be exceptionally stable in solution, showing only slightly diminished UV-vis absorption features after 3 days, even when exposed to an excess of thiol ligands.
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38
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The origin of the particle-size-dependent selectivity in 1-butene isomerization and hydrogenation on Pd/Al 2O 3 catalysts. Nat Commun 2021; 12:6098. [PMID: 34671045 PMCID: PMC8528898 DOI: 10.1038/s41467-021-26411-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Accepted: 10/01/2021] [Indexed: 11/29/2022] Open
Abstract
The selectivity of 1-butene hydrogenation/isomerization on Pd catalysts is known to be particle size dependent. Here we show that combining well-defined model catalysts, atmospheric pressure reaction kinetics, DFT calculations and microkinetic modeling enables to rationalize the particle size effect based on the abundance and the specific properties of the contributing surface facets.
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39
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Near-Infrared Femtosecond Laser Ablation of Au-Coated Ni: Effect of Organic Fluids and Water on Crater Morphology, Ablation Efficiency and Hydrodynamic Properties of NiAu Nanoparticles. MATERIALS (BASEL, SWITZERLAND) 2021; 14:5544. [PMID: 34639947 PMCID: PMC8509781 DOI: 10.3390/ma14195544] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/21/2021] [Revised: 09/17/2021] [Accepted: 09/21/2021] [Indexed: 11/16/2022]
Abstract
Scanning electron microscopy (SEM) and profilometry of the crater morphology and ablation efficiency upon femtosecond laser ablation of Au-coated Ni targets in various fluids revealed a pronounced dependence on the ablation medium. For ethanol, a sufficient ablation efficiency was obtained, whereas for 2-butanol a higher efficiency indicated stronger laser-target interaction. Hierarchical features in the crater periphery pointed to asymmetrical energy deposition or a residual effect of the Coulomb-explosion-initiating ablation. Significant beam deviation in 2-butanol caused maximum multiple scattering at the crater bottom. The highest values of microstrain and increased grain size, obtained from Williamson-Hall plots, indicated the superposition of mechanical stress, defect formation and propagation of fatigue cracks in the crater circumference. For n-hexane, deposition of frozen droplets in the outer crater region suggested a femtosecond-laser-induced phase explosion. A maximum ablation depth occurred in water, likely due to its high cooling efficiency. Grazing incidence micro X-ray diffraction (GIXRD) of the used target showed residual carbon and partial surface oxidation. The produced nanoparticle colloids were examined by multiangle dynamic light scattering (DLS), employing larger scattering angles for higher sensitivity toward smaller nanoparticles. The smallest nanoparticles were obtained in 2-butanol and ethanol. In n-hexane, floating carbon flakes originated from femtosecond-laser-induced solvent decomposition.
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40
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Single-Particle Catalysis: Revealing Intraparticle Pacemakers in Catalytic H 2 Oxidation on Rh. ACS Catal 2021; 11:10020-10027. [PMID: 34386273 PMCID: PMC8353627 DOI: 10.1021/acscatal.1c02384] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Revised: 07/14/2021] [Indexed: 11/30/2022]
Abstract
![]()
Self-sustained oscillations
in H2 oxidation on a Rh
nanotip mimicking a single catalytic nanoparticle were studied by in situ field emission microscopy (FEM). The observed spatio-temporal
oscillations result from the coupling of subsurface oxide formation/depletion
with reaction front propagation. An original sophisticated method
for tracking kinetic transition points allowed the identification
of local pacemakers, initiating kinetic transitions and the nucleation
of reaction fronts, with much higher temporal resolution than conventional
processing of FEM video files provides. The pacemakers turned out
to be specific surface atomic configurations at the border between
strongly corrugated Rh{973} regions and adjacent relatively flat terraces. These
structural ensembles are crucial for reactivity: while the corrugated
region allows sufficient oxygen incorporation under the Rh surface,
the flat terrace provides sufficient hydrogen supply required for
the kinetic transition, highlighting the importance of interfacet
communication. The experimental observations are complemented by mean-field
microkinetic modeling. The insights into the initiation and propagation
of kinetic transitions on a single catalytic nanoparticle demonstrate
how in situ monitoring of an ongoing reaction on
individual nanofacets can single out active configurations, especially
when combined with atomically resolving the nanoparticle surface by
field ion microscopy (FIM).
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41
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Operando Surface Spectroscopy and Microscopy during Catalytic Reactions: From Clusters via Nanoparticles to Meso-Scale Aggregates. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2021; 17:e2004289. [PMID: 33694320 DOI: 10.1002/smll.202004289] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 02/16/2021] [Indexed: 05/16/2023]
Abstract
Operando characterization of working catalysts, requiring per definitionem the simultaneous measurement of catalytic performance, is crucial to identify the relevant catalyst structure, composition and adsorbed species. Frequently applied operando techniques are discussed, including X-ray absorption spectroscopy, near ambient pressure X-ray photoelectron spectroscopy and infrared spectroscopy. In contrast to these area-averaging spectroscopies, operando surface microscopy by photoemission electron microscopy delivers spatially-resolved data, directly visualizing catalyst heterogeneity. For thorough interpretation, the experimental results should be complemented by density functional theory. The operando approach enables to identify changes of cluster/nanoparticle structure and composition during ongoing catalytic reactions and reveal how molecules interact with surfaces and interfaces. The case studies cover the length-scales from clusters via nanoparticles to meso-scale aggregates, and demonstrate the benefits of specific operando methods. Restructuring, ligand/atom mobility, and surface composition alterations during the reaction may have pronounced effects on activity and selectivity. The nanoscale metal/oxide interface steers catalytic performance via a long ranging effect. Combining operando spectroscopy with switching gas feeds or concentration-modulation provides further mechanistic insights. The obtained fundamental understanding is a prerequisite for improving catalytic performance and for rational design.
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42
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Resolving multifrequential oscillations and nanoscale interfacet communication in single-particle catalysis. Science 2021; 372:1314-1318. [PMID: 34016741 DOI: 10.1126/science.abf8107] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Revised: 02/17/2021] [Accepted: 05/05/2021] [Indexed: 11/02/2022]
Abstract
In heterogeneous catalysis research, the reactivity of individual nanofacets of single particles is typically not resolved. We applied in situ field electron microscopy to the apex of a curved rhodium crystal (radius of 650 nanometers), providing high spatial (~2 nanometers) and time resolution (~2 milliseconds) of oscillatory catalytic hydrogen oxidation, to image adsorbed species and reaction fronts on the individual facets. Using ionized water as the imaging species, the active sites were directly imaged with field ion microscopy. The catalytic behavior of differently structured nanofacets and the extent of coupling between them were monitored individually. We observed limited interfacet coupling, entrainment, frequency locking, and reconstruction-induced collapse of spatial coupling. The experimental results are backed up by microkinetic modeling of time-dependent oxygen species coverages and oscillation frequencies.
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Direct CO 2 capture and conversion to fuels on magnesium nanoparticles under ambient conditions simply using water. Chem Sci 2021; 12:5774-5786. [PMID: 35342542 PMCID: PMC8872847 DOI: 10.1039/d1sc01113h] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Accepted: 03/19/2021] [Indexed: 12/20/2022] Open
Abstract
Converting CO2 directly from the air to fuel under ambient conditions is a huge challenge. Thus, there is an urgent need for CO2 conversion protocols working at room temperature and atmospheric pressure, preferentially without any external energy input. Herein, we employ magnesium (nanoparticles and bulk), an inexpensive and the eighth-most abundant element, to convert CO2 to methane, methanol and formic acid, using water as the sole hydrogen source. The conversion of CO2 (pure, as well as directly from the air) took place within a few minutes at 300 K and 1 bar, and no external (thermal, photo, or electric) energy was required. Hydrogen was, however, the predominant product as the reaction of water with magnesium was favored over the reaction of CO2 and water with magnesium. A unique cooperative action of Mg, basic magnesium carbonate, CO2, and water enabled this CO2 transformation. If any of the four components was missing, no CO2 conversion took place. The reaction intermediates and the reaction pathway were identified by 13CO2 isotopic labeling, powder X-ray diffraction (PXRD), nuclear magnetic resonance (NMR) and in situ attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and rationalized by density-functional theory (DFT) calculations. During CO2 conversion, Mg was converted to magnesium hydroxide and carbonate, which may be regenerated. Our low-temperature experiments also indicate the future prospect of using this CO2-to-fuel conversion process on the surface of Mars, where CO2, water (ice), and magnesium are abundant. Thus, even though the overall process is non-catalytic, it could serve as a step towards a sustainable CO2 utilization strategy as well as potentially being a first step towards a magnesium-driven civilization on Mars. We demonstrated the use of magnesium nanoparticles (and bulk) to convert CO2 (pure & also from the air) to methane, methanol, formic acid and green cement without external energy within a few minutes, using only water as the sole hydrogen source.![]()
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Sum frequency generation spectroscopy in heterogeneous model catalysis: a minireview of CO-related processes. Catal Sci Technol 2021. [DOI: 10.1039/d0cy01736a] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Sum frequency generation (SFG) vibrational spectroscopy is applied to ambient pressure surface science studies of adsorption and catalytic reactions at solid/gas interfaces.
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Interplay between CO Disproportionation and Oxidation: On the Origin of the CO Reaction Onset on Atomic Layer Deposition-Grown Pt/ZrO 2 Model Catalysts. ACS Catal 2021; 11:208-214. [PMID: 33425478 PMCID: PMC7783867 DOI: 10.1021/acscatal.0c03974] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Revised: 11/04/2020] [Indexed: 11/29/2022]
Abstract
![]()
Pt/ZrO2 model catalysts were prepared by atomic layer
deposition (ALD) and examined at mbar pressure by operando sum frequency generation (SFG) spectroscopy and near-ambient pressure
X-ray photoelectron spectroscopy (NAP-XPS) combined with differentially
pumped mass spectrometry (MS). ALD enables creating model systems
ranging from Pt nanoparticles to bulk-like thin films. Polarization-dependent
SFG of CO adsorption reveals both the adsorption configuration and
the Pt particle morphology. By combining experimental data with ab initio density functional theory (DFT) calculations,
we show that the CO reaction onset is determined by a delicate balance
between CO disproportionation (Boudouard reaction) and oxidation.
CO disproportionation occurs on low-coordinated Pt sites, but only
at high CO coverages and when the remaining C atom is stabilized by
a favorable coordination. Thus, under the current conditions, initial
CO oxidation is found to be strongly influenced by the removal of
carbon deposits formed through disproportionation mechanisms rather
than being determined by the CO and oxygen inherent activity. Accordingly,
at variance with the general expectation, rough Pt nanoparticles are
seemingly less active than smoother Pt films. The applied approach
enables bridging both the “materials and pressure gaps”.
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An ultrahigh vacuum-compatible reaction cell for model catalysis under atmospheric pressure flow conditions. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2020; 91:125101. [PMID: 33379966 DOI: 10.1063/5.0026171] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Accepted: 11/06/2020] [Indexed: 06/12/2023]
Abstract
Atmospheric pressure reactions on model catalysts are typically performed in so-called high-pressure cells, with product analysis performed by gas chromatography (GC) or mass spectrometry (MS). However, in most cases, these cells have a large volume (liters) so that the reactions on catalysts with only cm2 surface area can be carried out only in the (recirculated) batch mode to accumulate sufficient product amounts. Herein, we describe a novel small-volume (milliliters) catalytic reactor that enables kinetic studies under atmospheric pressure flow conditions. The cell is located inside an ultrahigh vacuum chamber that is deliberately limited to basic functions. Model catalyst samples are mounted inside the reactor cell, which is locked to an oven for external heating and closed by using an extendable/retractable gas dosing tube. Reactant and product analyses are performed by both micro-GC and MS. The functionality of the new design is demonstrated by catalytic ethylene (C2H4) hydrogenation on polycrystalline Pt and Pd foils.
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47
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Dynamics of Pd Dopant Atoms inside Au Nanoclusters during Catalytic CO Oxidation. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2020; 124:23626-23636. [PMID: 33154783 PMCID: PMC7604939 DOI: 10.1021/acs.jpcc.0c05735] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Revised: 09/10/2020] [Indexed: 05/12/2023]
Abstract
Doping gold nanoclusters with palladium has been reported to increase their catalytic activity and stability. PdAu24 nanoclusters, with the Pd dopant atom located at the center of the Au cluster core, were supported on titania and applied in catalytic CO oxidation, showing significantly higher activity than supported monometallic Au25 nanoclusters. After pretreatment, operando DRIFTS spectroscopy detected CO adsorbed on Pd during CO oxidation, indicating migration of the Pd dopant atom from the Au cluster core to the cluster surface. Increasing the number of Pd dopant atoms in the Au structure led to incorporation of Pd mostly in the S-(M-S) n protecting staples, as evidenced by in situ XAFS. A combination of oxidative and reductive thermal pretreatment resulted in the formation of isolated Pd surface sites within the Au surface. The combined analysis of in situ XAFS, operando DRIFTS, and ex situ XPS thus revealed the structural evolution of bimetallic PdAu nanoclusters, yielding a Pd single-site catalyst of 2.7 nm average particle size with improved CO oxidation activity.
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Hydrogenation on Palladium Nanoparticles Supported by Graphene Nanoplatelets. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2020; 124:23674-23682. [PMID: 33154784 PMCID: PMC7604937 DOI: 10.1021/acs.jpcc.0c06636] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Revised: 10/06/2020] [Indexed: 05/28/2023]
Abstract
Pd nanoparticles (1 wt %; mean size ∼4 nm) were supported on ∼2 μm sized, but few nanometers thick, graphene nanoplatelets (GNPs) and compared to 1 wt % Pd on activated carbon or γ-alumina. Catalyst morphology, specific surface area, and Pd particle size were characterized by SEM, BET, and TEM, respectively. H2-TPD indicated that GNPs intercalated hydrogen, which may provide additional H2 supply to the Pd nanoparticles during C2H4 hydrogenation. Whereas the two types of Pd/GNPs (NaOH vs calcinated) catalysts were less active than Pd/C and Pd/Al2O3 below 40 °C, at 55 °C they were about 3-4 times more active. As for example Pd/GNPs (NaOH) and Pd/Al2O3 exhibited not too different mean Pd particle size (3.7 vs 2.5 nm, respectively), the higher activity is attributed to the additional hydrogen supply likely by the metal/support interface, as suggested by the varying C2H4 and H2 orders on the different supports. Operando XANES measurements during C2H4 hydrogenation revealed the presence of Pd hydride. The Pd hydride was more stable for Pd/GNPs (NaOH) than for Pd/C, once more pointing to a better hydrogen supply by graphene nanoplatelets.
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Fast visual evaluation of the catalytic activity of CeO2: Simple colorimetric assay using 3,3′,5,5′-tetramethylbenzidine as indicator. J Catal 2020. [DOI: 10.1016/j.jcat.2020.05.016] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Coverage-Induced Orientation Change: CO on Ir(111) Monitored by Polarization-Dependent Sum Frequency Generation Spectroscopy and Density Functional Theory. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2020; 124:18102-18111. [PMID: 32855760 PMCID: PMC7444014 DOI: 10.1021/acs.jpcc.0c04986] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Revised: 07/21/2020] [Indexed: 05/16/2023]
Abstract
Polarization-dependent sum frequency generation (SFG) spectroscopy was applied to study the adsorption of carbon monoxide (CO) on the well-ordered (annealed) Ir(111) single-crystal surface at various CO coverages. Coverage was adjusted by varying the substrate temperature (300-575 K) and/or gas pressure (10-7 to 1.0 mbar). Under all conditions investigated, only a single absorption band at 2038-2094 cm-1 was observed, characteristic of linearly bonded (on-top) CO. Using different polarizations, PPP and SSP spectra were acquired with a high signal-to-noise ratio, whereby tilt angles of CO on Ir(111) could be determined for the first time by SFG. It was found that not only the vibrational frequency of on-top CO but also the tilt angle was strongly coverage-dependent. The higher the coverage was, the larger the vibrational frequency and the tilt angle were. At about 0.7 ML coverage, a CO tilt angle of at least 20° was observed, which is in good agreement with density functional theory (DFT) calculations. In addition, the molecular hyperpolarizability ratio (R) of CO (at 0.13 ML in UHV) was determined to be 0.08. Based on the combined SFG/DFT results, it may change to 0.29 at 0.77 ML coverage.
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