1
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Lithium-Directed Transformation of Amorphous Iridium (Oxy)hydroxides To Produce Active Water Oxidation Catalysts. J Am Chem Soc 2023; 145:6398-6409. [PMID: 36892000 PMCID: PMC10037335 DOI: 10.1021/jacs.2c13567] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/10/2023]
Abstract
The oxygen evolution reaction (OER) is crucial to future energy systems based on water electrolysis. Iridium oxides are promising catalysts due to their resistance to corrosion under acidic and oxidizing conditions. Highly active iridium (oxy)hydroxides prepared using alkali metal bases transform into low activity rutile IrO2 at elevated temperatures (>350 °C) during catalyst/electrode preparation. Depending on the residual amount of alkali metals, we now show that this transformation can result in either rutile IrO2 or nano-crystalline Li-intercalated IrOx. While the transition to rutile results in poor activity, the Li-intercalated IrOx has comparative activity and improved stability when compared to the highly active amorphous material despite being treated at 500 °C. This highly active nanocrystalline form of lithium iridate could be more resistant to industrial procedures to produce PEM membranes and provide a route to stabilize the high populations of redox active sites of amorphous iridium (oxy)hydroxides.
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2
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Selective Ammoximation of Ketones via In Situ H 2O 2 Synthesis. ACS Catal 2023. [DOI: 10.1021/acscatal.2c05799] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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3
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Lowering the Operating Temperature of Gold Acetylene Hydrochlorination Catalysts Using Oxidized Carbon Supports. ACS Catal 2022. [DOI: 10.1021/acscatal.2c04242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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4
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N-Heterocyclic Carbene Modified Palladium Catalysts for the Direct Synthesis of Hydrogen Peroxide. J Am Chem Soc 2022; 144:15431-15436. [PMID: 35976628 PMCID: PMC9449981 DOI: 10.1021/jacs.2c04828] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
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Heterogeneous palladium catalysts modified by N-heterocyclic
carbenes
(NHCs) are shown to be highly effective toward the direct synthesis
of hydrogen peroxide (H2O2), in the absence
of the promoters which are typically required to enhance both activity
and selectivity. Catalytic evaluation in a batch regime demonstrated
that through careful selection of the N-substituent of the NHC it
is possible to greatly enhance catalytic performance when compared
to the unmodified analogue and reach concentrations of H2O2 rivaling that obtained by state-of-the-art catalysts.
The enhanced performance of the modified catalyst, which is retained
upon reuse, is attributed to the ability of the NHC to electronically
modify Pd speciation.
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5
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Highly efficient catalytic production of oximes from ketones using in situ-generated H 2O 2. Science 2022; 376:615-620. [PMID: 35511983 DOI: 10.1126/science.abl4822] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The ammoximation of cyclohexanone using preformed hydrogen peroxide (H2O2) is currently applied commercially to produce cyclohexanone oxime, an important feedstock in nylon-6 production. We demonstrate that by using supported gold-palladium (AuPd) alloyed nanoparticles in conjunction with a titanium silicate-1 (TS-1) catalyst, H2O2 can be generated in situ as needed, producing cyclohexanone oxime with >95% selectivity, comparable to the current industrial route. The ammoximation of several additional simple ketones is also demonstrated. Our approach eliminates the need to transport and store highly concentrated, stabilized H2O2, potentially achieving substantial environmental and economic savings. This approach could form the basis of an alternative route to numerous chemical transformations that are currently dependent on a combination of preformed H2O2 and TS-1, while allowing for considerable process intensification.
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6
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Analysing the relationship between the fields of thermo- and electrocatalysis taking hydrogen peroxide as a case study. Nat Commun 2022; 13:1973. [PMID: 35418132 PMCID: PMC9007970 DOI: 10.1038/s41467-022-29536-6] [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: 08/27/2021] [Accepted: 03/01/2022] [Indexed: 11/29/2022] Open
Abstract
Research in thermo- and electrocatalysis have often preceded in isolation, even for similar reactions. Here, the authors compare current trends in both fields and elaborate on the commonalities and differences with a specific focus on the production of hydrogen peroxide.
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7
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Acceptorless dehydrogenation of 1-phenylethanol using Pd/TiO2 catalysts prepared by sol immobilisation. CATAL COMMUN 2022. [DOI: 10.1016/j.catcom.2021.106377] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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8
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Improving the performance of Pd based catalysts for the direct synthesis of hydrogen peroxide via acid incorporation during catalyst synthesis. CATAL COMMUN 2021. [DOI: 10.1016/j.catcom.2021.106358] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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9
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A residue-free approach to water disinfection using catalytic in situ generation of reactive oxygen species. Nat Catal 2021. [DOI: 10.1038/s41929-021-00642-w] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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10
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Abstract
Methane represents one of the most abundant carbon sources for fuel or chemical production. However, remote geographical locations and high transportation costs result in a substantial proportion being flared at the source. The selective oxidation of methane to methanol remains a grand challenge for catalytic chemistry due to the large energy barrier for the initial C-H activation and prevention of overoxidation to CO2. Indirect methods such as steam reforming produce CO and H2 chemical building blocks, but they consume large amounts of energy over multistage processes. This makes the development of the low-temperature selective oxidation of methane to methanol highly desirable and explains why it has remained an active area of research over the last 50 years.The thermodynamically favorable oxidation of methane to methanol would ideally use only molecular oxygen. Nature effects this transformation with the enzyme methane monooxygenase (MMO) in aqueous solution at ambient temperature with the addition of 2 equiv of a reducing cofactor. MMO active sites are Fe and Cu oxoclusters, and the incorporation of these metals into zeolitic frameworks can result in biomimetic activity. Most approaches to methane oxidation using metal-doped zeolites use high temperature with oxygen or N2O; however, demonstrations of catalytic cycles without catalyst regeneration cycles are limited. Over the last 10 years, we have developed Fe-Cu-ZSM-5 materials for the selective oxidation of methane to methanol under aqueous conditions at 50 °C using H2O2 as an oxidant (effectively O2 + 2 reducing equiv), which compete with MMO in terms of activity. To date, these materials are among the most active and selective catalysts for methane oxidation under this mild condition, but industrially, H2O2 is an expensive oxidant to use in the production of methanol.This observation of activity under mild conditions led to new approaches to utilize O2 as the oxidant. Supported precious metal nanoparticles have been shown to be active for a range of C-H activation reactions using O2 and H2O2, but the rapid decomposition of H2O2 over metal surfaces limits efficiency. We identified that this decomposition could be minimized by removing the support material and carrying out the reaction with colloidal AuPd nanoparticles. The efficiency of methanol production with H2O2 consumption was increased by 4 orders of magnitude, and crucially it was demonstrated for the first time that molecular O2 could be incorporated into the methanol produced with 91% selectivity. The understanding gained from these two approaches provides valuable insight into possible new routes to selective methane oxidation which will be presented here in the context of our own research in this area.
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11
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Sulfur Promotion in Au/C Catalyzed Acetylene Hydrochlorination. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2021; 17:e2007221. [PMID: 33629821 DOI: 10.1002/smll.202007221] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 12/19/2020] [Indexed: 06/12/2023]
Abstract
The formation of highly active and stable acetylene hydrochlorination catalysts is of great industrial importance. The successful replacement of the highly toxic mercuric chloride catalyst with gold has led to a flurry of research in this area. One key aspect, which led to the commercialization of the gold catalyst is the use of thiosulphate as a stabilizing ligand. This study investigates the use of a range of sulfur containing compounds as promoters for production of highly active Au/C catalysts. Promotion is observed across a range of metal sulfates, non-metal sulfates, and sulfuric acid treatments. This observed enhancement can be optimized by careful consideration of either pre- or post-treatments, concentration of dopants used, and modification of washing steps. Pre-treatment of the carbon support with sulfuric acid (0.76 m) resulted in the most active Au/C in this series with an acetylene conversion of ≈70% at 200 °C.
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12
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Ambient base-free glycerol oxidation over bimetallic PdFe/SiO2 by in situ generated active oxygen species. RESEARCH ON CHEMICAL INTERMEDIATES 2021. [DOI: 10.1007/s11164-020-04333-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
AbstractLow temperature oxidation of alcohols over heterogeneous catalysts is exceptionally challenging, particularly under neutral conditions. Herein, we report on an efficient, base-free method to oxidise glycerol over a 0.5%Pd-0.5%Fe/SiO2 catalyst at ambient temperature in the presence of gaseous H2 and O2. The exceptional catalytic performance was attributed to the in situ formation of highly reactive surface-bound oxygenated species, which promote the dehydrogenation on the alcohol. The PdFe bimetallic catalyst was determined to be significantly more active than corresponding monometallic analogues, highlighting the important role both metals have in this oxidative transformation. Fe leaching was confirmed to occur over the course of the reaction but sequestering experiments, involving the addition of bare carbon to the reactions, confirmed that the reaction was predominantly heterogeneous in nature. Investigations with electron paramagnetic resonance spectroscopy suggested that the reactivity in the early stages was mediated by surface-bound reactive oxygen species; no homogeneous radical species were observed in solution. This theory was further evidenced by a direct H2O2 synthesis study, which confirmed that the presence of Fe in the bimetallic catalyst neither improved the synthesis of H2O2 nor promoted its decomposition over the PdFe/SiO2 catalyst.
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13
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Preparation of Solid Solution and Layered IrOx–Ni(OH)2 Oxygen Evolution Catalysts: Toward Optimizing Iridium Efficiency for OER. ACS Catal 2020. [DOI: 10.1021/acscatal.0c03866] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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14
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The oxygen reduction reaction on palladium with low metal loadings: The effects of chlorides on the stability and activity towards hydrogen peroxide. J Catal 2020. [DOI: 10.1016/j.jcat.2020.06.019] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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15
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Author Correction: Tuning of catalytic sites in Pt/TiO2 catalysts for the chemoselective hydrogenation of 3-nitrostyrene. Nat Catal 2020. [DOI: 10.1038/s41929-020-00500-1] [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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16
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The direct synthesis of hydrogen peroxide from H 2 and O 2 using Pd-Ni/TiO 2 catalysts. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2020; 378:20200062. [PMID: 32623987 PMCID: PMC7422896 DOI: 10.1098/rsta.2020.0062] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 05/05/2020] [Indexed: 06/11/2023]
Abstract
The direct synthesis of hydrogen peroxide (H2O2) from molecular H2 and O2 offers an attractive, decentralized alternative to production compared to the current means of production, the anthraquinone process. Herein we evaluate the performance of a 0.5%Pd-4.5%Ni/TiO2 catalyst in batch and flow reactor systems using water as a solvent at ambient temperature. These reaction conditions are considered challenging for the synthesis of high H2O2 concentrations, with the use of sub-ambient temperatures and alcohol co-solvents typical. Catalytic activity was observed to be stable to prolonged use in multiple batch experiments or in a flow system, with selectivities towards H2O2 of 97% and 85%, respectively. This study was carried out in the absence of halide or acid additives that are typically used to inhibit sequential H2O2 degradation reactions showing that this Pd-Ni catalyst has the potential to produce H2O2 selectively. This article is part of a discussion meeting issue 'Science to enable the circular economy'.
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17
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In situ K-edge X-ray absorption spectroscopy of the ligand environment of single-site Au/C catalysts during acetylene hydrochlorination. Chem Sci 2020; 11:7040-7052. [PMID: 34122997 PMCID: PMC8159275 DOI: 10.1039/d0sc02152k] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The replacement of HgCl2/C with Au/C as a catalyst for acetylene hydrochlorination represents a significant reduction in the environmental impact of this industrial process. Under reaction conditions atomically dispersed cationic Au species are the catalytic active site, representing a large-scale application of heterogeneous single-site catalysts. While the metal nuclearity and oxidation state under operating conditions has been investigated in catalysts prepared from aqua regia and thiosulphate, limited studies have focused on the ligand environment surrounding the metal centre. We now report K-edge soft X-ray absorption spectroscopy of the Cl and S ligand species used to stabilise these isolated cationic Au centres in the harsh reaction conditions. We demonstrate the presence of three distinct Cl species in the materials; inorganic Cl-, Au-Cl, and C-Cl and how these species evolve during reaction. Direct evidence of Au-S interactions is confirmed in catalysts prepared using thiosulfate precursors which show high stability towards reduction to inactive metal nanoparticles. This stability was clear during gas switching experiments, where exposure to C2H2 alone did not dramatically alter the Au electronic structure and consequently did not deactivate the thiosulfate catalyst.
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18
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Isolated Pd Sites as Selective Catalysts for Electrochemical and Direct Hydrogen Peroxide Synthesis. ACS Catal 2020. [DOI: 10.1021/acscatal.0c01305] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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19
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Facile synthesis of precious-metal single-site catalysts using organic solvents. Nat Chem 2020; 12:560-567. [DOI: 10.1038/s41557-020-0446-z] [Citation(s) in RCA: 58] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2019] [Accepted: 02/20/2020] [Indexed: 11/09/2022]
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20
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The direct synthesis of hydrogen peroxide using a combination of a hydrophobic solvent and water. Catal Sci Technol 2020. [DOI: 10.1039/d0cy01163k] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The use of a hydrophobic solvent in combination with water leads to significant suppression of H2O2 degradation pathways over a AuPd/C catalyst.
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21
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Gold–palladium colloids as catalysts for hydrogen peroxide synthesis, degradation and methane oxidation: effect of the PVP stabiliser. Catal Sci Technol 2020. [DOI: 10.1039/d0cy00915f] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
PVP polymer stabilisers effect the reactivity of AuPd nanoparticles towards H2O2 synthesis/decomposition and methane oxidation.
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22
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The Effect of Polymer Addition on Base Catalysed Glycerol Oxidation Using Gold and Gold–Palladium Bimetallic Catalysts. Top Catal 2019. [DOI: 10.1007/s11244-019-01212-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Abstract
The oxidation of glycerol represents both a viable route to catalytic upgrading of biomass and has become a model reaction for catalytic polyol oxidation. Gold and gold–palladium nanoparticle catalysts prepared by colloidal methods involving polymer additives have been extensively studied. However, the effect of residual polymer at the catalyst surface on reaction pathways has not been decoupled from particle size effects. We show that when using catalysts prepared without polymer stabilisers the addition of either polyvinyl alcohol or polyvinylpyrrolidone to the reaction changes the reaction rate and results in a change in reaction selectivity. We conclude that the polymer additive has a significant effect on the reaction pathway and that these systems should be considered as a metal surface–polymer interface catalytic systems and properties should not be rationalised solely based on nanoparticle size.
Graphic Abstract
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23
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Tuning of catalytic sites in Pt/TiO2 catalysts for the chemoselective hydrogenation of 3-nitrostyrene. Nat Catal 2019. [DOI: 10.1038/s41929-019-0334-3] [Citation(s) in RCA: 106] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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24
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A chemo-enzymatic oxidation cascade to activate C-H bonds with in situ generated H 2O 2. Nat Commun 2019; 10:4178. [PMID: 31519878 PMCID: PMC6744418 DOI: 10.1038/s41467-019-12120-w] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Accepted: 08/16/2019] [Indexed: 11/09/2022] Open
Abstract
Continuous low-level supply or in situ generation of hydrogen peroxide (H2O2) is essential for the stability of unspecific peroxygenases, which are deemed ideal biocatalysts for the selective activation of C-H bonds. To envisage potential large scale applications of combined catalytic systems the reactions need to be simple, efficient and produce minimal by-products. We show that gold-palladium nanoparticles supported on TiO2 or carbon have sufficient activity at ambient temperature and pressure to generate H2O2 from H2 and O2 and supply the oxidant to the engineered unspecific heme-thiolate peroxygenase PaDa-I. This tandem catalyst combination facilitates efficient oxidation of a range of C-H bonds to hydroxylated products in one reaction vessel with only water as a by-product under conditions that could be easily scaled.
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25
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Abstract
Abstract
Au nanoparticles supported on P25 TiO2 (Au/TiO2) were prepared by a facile sol-immobilisation method and investigated for the surface plasmon-assisted glycerol oxidation under base-free conditions. The Au/TiO2 samples were characterized by UV–vis spectroscopy and transmission electron microscopy. Catalysts were prepared using polyvinyl alcohol as stabiliser as well as in the absence of polymer stabiliser. Both the conversion and the reaction selectivity are affected by the plasmon-assisted oxidation and there is an interplay between the presence of the stabiliser and the Au nanoparticle size.
Graphic Abstract
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26
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Enhanced Activity and Stability of Gold/Ceria-Titania for the Low-Temperature Water-Gas Shift Reaction. Front Chem 2019; 7:443. [PMID: 31259170 PMCID: PMC6587040 DOI: 10.3389/fchem.2019.00443] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Accepted: 05/29/2019] [Indexed: 11/13/2022] Open
Abstract
Gold supported on ceria-zirconia is one of the most active low temperature water-gas shift catalysts reported to date but rapid deactivation occurs under reaction conditions. In this study, ceria-titania was evaluated as an alternative catalyst support. Materials of different Ce:Ti compositions were synthesized using a sol-gel methodology and gold was supported onto these using a deposition-precipitation method. They were then investigated as catalysts for the low-temperature water-gas shift reaction. Au/Ce0.2Ti0.8O2 exhibited superior activity and stability to a highly active, previously reported gold catalyst supported on ceria-zirconia. High activity and stability was found to be related to the support comprising a high number of oxygen defect sites and a high specific surface area. These properties were conducive to forming a highly active catalyst with well-dispersed Au species.
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27
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Synthesis of highly uniform and composition-controlled gold-palladium supported nanoparticles in continuous flow. NANOSCALE 2019; 11:8247-8259. [PMID: 30976773 DOI: 10.1039/c8nr09917k] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The synthesis of supported bimetallic nanoparticles with well-defined size and compositional parameters has long been a challenge. Although batch colloidal methods are commonly used to pre-form metal nanoparticles with the desired size-range in solution, inhomogeneous mixing of the reactant solutions often leads to variations in size, structure and composition from batch-to-batch and even particle-to-particle. Here we describe a millifluidic approach for the production of oxide supported monometallic Au and bimetallic AuPd nanoparticles in a continuous fashion. This optimised method enables the production of nanoparticles with smaller mean sizes, tighter particle size distributions and a more uniform particle-to-particle chemical composition as compared to the conventional batch procedure. In addition, we describe a facile procedure to prepare bimetallic Au@Pd core-shell nanoparticles in continuous flow starting from solutions of the metal precursors. Moreover, the relative ease of scalability of this technique makes the proposed methodology appealing not only for small-scale laboratory purposes, but also for the industrial-scale production of supported metal nanoparticles.
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28
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Abstract
AuPd nanoparticles supported on P25 TiO2 (AuPd/TiO2) were prepared by a facile sol-immobilisation method and investigated for surface plasmon-assisted glycerol oxidation under base-free conditions.
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29
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Oxidative Degradation of Phenol using in situ Generated Hydrogen Peroxide Combined with Fenton’s Process. JOHNSON MATTHEY TECHNOLOGY REVIEW 2018. [DOI: 10.1595/205651318x15302623075041] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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30
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Homocoupling of Phenylboronic Acid using Atomically Dispersed Gold on Carbon Catalysts: Catalyst Evolution Before Reaction. ChemCatChem 2018. [DOI: 10.1002/cctc.201701840] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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31
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Glycerol Oxidation Using MgO- and Al2
O3
-supported Gold and Gold-Palladium Nanoparticles Prepared in the Absence of Polymer Stabilizers. ChemCatChem 2018. [DOI: 10.1002/cctc.201800074] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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32
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Abstract
We report the catalytic performance of Au–Pd nanoparticles prepared via a sol immobilisation technique for the catalytic hydrogenation of cinnamaldehyde under mild reaction conditions.
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33
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Activation and Deactivation of Gold/Ceria-Zirconia in the Low-Temperature Water-Gas Shift Reaction. Angew Chem Int Ed Engl 2017; 56:16037-16041. [PMID: 29034566 DOI: 10.1002/anie.201709708] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Indexed: 11/10/2022]
Abstract
Gold (Au) on ceria-zirconia is one of the most active catalysts for the low-temperature water-gas shift reaction (LTS), a key stage of upgrading H2 reformate streams for fuel cells. However, this catalyst rapidly deactivates on-stream and the deactivation mechanism remains unclear. Using stop-start scanning transmission electron microscopy to follow the exact same area of the sample at different stages of the LTS reaction, as well as complementary X-ray photoelectron spectroscopy, we observed the activation and deactivation of the catalyst at various stages. During the heating of the catalyst to reaction temperature, we observed the formation of small Au nanoparticles (NPs; 1-2 nm) from subnanometer Au species. These NPs were then seen to agglomerate further over 48 h on-stream, and most rapidly in the first 5 h when the highest rate of deactivation was observed. These findings suggest that the primary deactivation process consists of the loss of active sites through the agglomeration and possible dewetting of Au NPs.
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34
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Activation and Deactivation of Gold/Ceria–Zirconia in the Low‐Temperature Water–Gas Shift Reaction. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201709708] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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35
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Aqueous Au-Pd colloids catalyze selective CH4oxidation to CH3OH with O2under mild conditions. Science 2017; 358:223-227. [DOI: 10.1126/science.aan6515] [Citation(s) in RCA: 331] [Impact Index Per Article: 47.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2017] [Accepted: 08/25/2017] [Indexed: 01/22/2023]
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36
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Inside Back Cover: Highly Active Gold and Gold-Palladium Catalysts Prepared by Colloidal Methods in the Absence of Polymer Stabilizers (ChemCatChem 15/2017). ChemCatChem 2017. [DOI: 10.1002/cctc.201701176] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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37
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38
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Solid Acid Additives as Recoverable Promoters for the Direct Synthesis of Hydrogen Peroxide. Ind Eng Chem Res 2017. [DOI: 10.1021/acs.iecr.7b01800] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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39
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Highly Active Gold and Gold–Palladium Catalysts Prepared by Colloidal Methods in the Absence of Polymer Stabilizers. ChemCatChem 2017. [DOI: 10.1002/cctc.201700483] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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40
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Identification of single-site gold catalysis in acetylene hydrochlorination. Science 2017; 355:1399-1403. [DOI: 10.1126/science.aal3439] [Citation(s) in RCA: 299] [Impact Index Per Article: 42.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Accepted: 03/07/2017] [Indexed: 01/30/2023]
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41
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42
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Acetylene hydrochlorination using Au/carbon: a journey towards single site catalysis. Chem Commun (Camb) 2017; 53:11733-11746. [DOI: 10.1039/c7cc05986h] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The replacement of mercuric chloride in the production of vinyl chloride monomer, a precursor to PVC, would greatly reduce the environmental impact of this large scale industrial process.
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Addressing stability challenges of using bimetallic electrocatalysts: the case of gold–palladium nanoalloys. Catal Sci Technol 2017. [DOI: 10.1039/c7cy00291b] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Studying changes in surface composition of bimetallic (AuPd) catalysts under dealloying is of key importance for predicting their stability during application.
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Synergy and Anti-Synergy between Palladium and Gold in Nanoparticles Dispersed on a Reducible Support. ACS Catal 2016; 6:6623-6633. [PMID: 27990317 PMCID: PMC5154324 DOI: 10.1021/acscatal.6b01275] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Revised: 08/03/2016] [Indexed: 11/28/2022]
Abstract
Highly active and stable bimetallic Au-Pd catalysts have been extensively studied for several liquid-phase oxidation reactions in recent years, but there are far fewer reports on the use of these catalysts for low-temperature gas-phase reactions. Here we initially established the presence of a synergistic effect in a range of bimetallic Au-Pd/CeZrO4 catalysts, by measuring their activity for selective oxidation of benzyl alcohol. The catalysts were then evaluated for low-temperature WGS, CO oxidation, and formic acid decomposition, all of which are believed to be mechanistically related. A strong anti-synergy between Au and Pd was observed for these reactions, whereby the introduction of Pd to a monometallic Au catalyst resulted in a significant decrease in catalytic activity. Furthermore, monometallic Pd was more active than Pd-rich bimetallic catalysts. The nature of the anti-synergy was probed by several ex situ techniques, which all indicated a growth in metal nanoparticle size with Pd addition. However, the most definitive information was provided by in situ CO-DRIFTS, in which CO adsorption associated with interfacial sites was found to vary with the molar ratio of the metals and could be correlated with the catalytic activity of each reaction. As a similar correlation was observed between activity and the presence of Au0* (as detected by XPS), it is proposed that peripheral Au0* species form part of the active centers in the most active catalysts for the three gas-phase reactions. In contrast, the active sites for the selective oxidation of benzyl alcohol are generally thought to be electronically modified gold atoms at the surface of the nanoparticles.
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Population and hierarchy of active species in gold iron oxide catalysts for carbon monoxide oxidation. Nat Commun 2016; 7:12905. [PMID: 27671143 PMCID: PMC5052626 DOI: 10.1038/ncomms12905] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2015] [Accepted: 08/12/2016] [Indexed: 12/03/2022] Open
Abstract
The identity of active species in supported gold catalysts for low temperature carbon monoxide oxidation remains an unsettled debate. With large amounts of experimental evidence supporting theories of either gold nanoparticles or sub-nm gold species being active, it was recently proposed that a size-dependent activity hierarchy should exist. Here we study the diverging catalytic behaviours after heat treatment of Au/FeOx materials prepared via co-precipitation and deposition precipitation methods. After ruling out any support effects, the gold particle size distributions in different catalysts are quantitatively studied using aberration corrected scanning transmission electron microscopy (STEM). A counting protocol is developed to reveal the true particle size distribution from HAADF-STEM images, which reliably includes all the gold species present. Correlation of the populations of the various gold species present with catalysis results demonstrate that a size-dependent activity hierarchy must exist in the Au/FeOx catalyst.
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Continuous selective oxidation of methane to methanol over Cu- and Fe-modified ZSM-5 catalysts in a flow reactor. Catal Today 2016. [DOI: 10.1016/j.cattod.2015.09.011] [Citation(s) in RCA: 90] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Direct synthesis of hydrogen peroxide in water at ambient temperature. Proc Math Phys Eng Sci 2016; 472:20160156. [PMID: 27436982 PMCID: PMC4950207 DOI: 10.1098/rspa.2016.0156] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Accepted: 05/26/2016] [Indexed: 11/12/2022] Open
Abstract
The direct synthesis of hydrogen peroxide (H2O2) from hydrogen and oxygen has been studied using an Au-Pd/TiO2 catalyst. The aim of this study is to understand the balance of synthesis and sequential degradation reactions using an aqueous, stabilizer-free solvent at ambient temperature. The effects of the reaction conditions on the productivity of H2O2 formation and the undesirable hydrogenation and decomposition reactions are investigated. Reaction temperature, solvent composition and reaction time have been studied and indicate that when using water as the solvent the H2O2 decomposition reaction is the predominant degradation pathway, which provides new challenges for catalyst design, which has previously focused on minimizing the subsequent hydrogenation reaction. This is of importance for the application of this catalytic approach for water purification.
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Gas phase stabiliser-free production of hydrogen peroxide using supported gold-palladium catalysts. Chem Sci 2016; 7:5833-5837. [PMID: 30034723 PMCID: PMC6024239 DOI: 10.1039/c6sc01332e] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Accepted: 05/10/2016] [Indexed: 11/21/2022] Open
Abstract
Hydrogen peroxide synthesis from hydrogen and oxygen in the gas phase is postulated to be a key reaction step in the gas phase epoxidation of propene using gold-titanium silicate catalysts. During this process H2O2 is consumed in a secondary step to oxidise an organic molecule so is typically not observed as a reaction product. We demonstrate that using AuPd nanoparticles, which are known to have high H2O2 synthesis rates in the liquid phase, it is possible to not only oxidise organic molecules in the gas phase but to detect H2O2 for the first time as a reaction product in both a fixed bed reactor and a pulsed Temporal Analysis of Products (TAP) reactor without stabilisers present in the gas feed. This observation opens up possibility of synthesising H2O2 directly using a gas phase reaction.
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Investigation of the active species in the carbon-supported gold catalyst for acetylene hydrochlorination. Catal Sci Technol 2016. [DOI: 10.1039/c6cy00090h] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The active site for a Au/C catalysts for acetylene hydrochlorination involves a Au+–Au3+ couple.
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