Higher loadings of Pt single atoms and clusters over reducible metal oxides: application to C–O bond activation

Wang, Yunzhu; Lee, Seungyeon; Zhou, Jiahua; Fu, Jiayi; Foucher, Alexandre C.; Stach, Eric A.; Ma, Lu; Marinković, Nebojša; Zheng, Weiqing; Vlachos, Dionisios G.

doi:10.1039/d2cy00193d

Cited by 9 publications

(11 citation statements)

References 61 publications

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“…Thermal catalytic hydrogenation over supported metal catalysts is among the most valuable synthetic pathways to make fuels and chemicals. − The widely accepted Langmuir–Hinshelwood (L-H) mechanism involves H 2 and substrate co-adsorption on a metal surface followed by hydrogen atom transfer to the targeted molecules. − While hydrogenation processes are also common in electro-, photo-, and biological catalytic systems, a distinct feature is that H + instead of H 2 is often used as a hydrogen source, together with photo-, chemical-, or electro-induced electrons serving as a reductant. − Therefore, most of these hydrogenation processes proceed via sequential proton–electron-transfer steps. − Taking electrocatalytic reduction of nitro compounds as an example, the nitro group receives different amounts of electrons and protons to form nitroso, azoxy, azo compounds, hydroxylamines, and amines . The transfer of the first electron to the nitro group produces a radical anion, which can directly capture a proton from the solvent.…”

Section: Introductionmentioning

confidence: 99%

Demonstrating the Electron–Proton-Transfer Mechanism of Aqueous Phase 4-Nitrophenol Hydrogenation Using Unbiased Electrochemical Cells

Sun

Hülsey

et al. 2022

ACS Catal.

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Heterogeneous thermocatalytic hydrogenation is widely believed to occur via co-adsorption of H 2 and other reactants, but in aqueous phase an ionic or electrochemical mechanism was also proposed. Herein, we conduct 4-nitrophenol hydrogenation in an unbiased H-cell, where the H 2 and substrate are separately supplied into two chambers connected by a proton exchange membrane, in comparison with the same reaction in a single cell in which H 2 and 4-nitrophenol are co-fed. Based on the observation of the almost identical hydrogenation performance between the H-cell and the single cell, we conclude that coadsorption of H 2 and 4-nitrophenol is not a prerequisite for hydrogenation in aqueous phase in the tested pH range. Isotope experiments, scavenger test, DFT calculations, and reaction kinetics suggest that a coupled electrochemical half-reaction mechanism for 4-nitrophenol hydrogenation in acidic aqueous phase is predominant. Importantly, while H 2 oxidation primarily occurs on metal sites, 4-nitrophenol reduction occurs on both metal sites and conductive support, highlighting the non-innocent role of the support if the hydrogenation reaction follows the electron− proton-transfer pathway.

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Section: Introductionmentioning

confidence: 99%

Demonstrating the Electron–Proton-Transfer Mechanism of Aqueous Phase 4-Nitrophenol Hydrogenation Using Unbiased Electrochemical Cells

Sun

Hülsey

et al. 2022

ACS Catal.

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“…Due to the very nature of these atomically dispersed catalysts, the lack of metal–metal bonding and the heterogeneity of multiple binding geometries wash out the EXAFS signal beyond the first peak in r-space. Given that in most studied SACs and SAAs based on Pt, ,− Rh, − Pd, ,, Ir, − and Co ,− the XANES features are often quite featureless, the methods of data modeling are severely limited in their ability to perform their speciation quantitatively and, in many cases, even qualitatively.…”

Section: Heterogeneity Of Atomically Dispersed Catalysts (Sacs)mentioning

confidence: 99%

Speciation of Nanocatalysts Using X-ray Absorption Spectroscopy Assisted by Machine Learning

2023

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The structure and morphology of supported nanoparticle catalysts play important roles in many industrial reactions. Recent progress has identified key aspects of structure−activity relationships at the nanoscale and novel methods to study the local environment of the active sites. X-ray absorption fine structure (XAFS) spectroscopy, despite being a leading technique for this purpose, is hampered significantly by its ensemble-averaging nature which often leads to a bias toward a single "representative" structure. Learning heterogeneous distributions of nanostructures at the inter-and intraparticle levels from the average XAFS spectrum is a formidable challenge that can be overcome in some cases described in this Perspective. We also discuss emerging machine learning techniques for extracting the information about the heterogeneity of metal species from XAFS data.

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“…S26). Catalyst regeneration from sintering can be overcome by redispersion or encapsulation methods developed recently [29][30][31] .…”

Section: Catalyst Recyclabilitymentioning

confidence: 99%

Selective hydrogenation via precise hydrogen bond interactions on catalytic scaffolds

et al. 2023

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The active site environment in enzymes has been known to affect catalyst performance through weak interactions with a substrate, but precise synthetic control of enzyme inspired heterogeneous catalysts remains challenging. Here, we synthesize hyper-crosslinked porous polymer (HCPs) with solely -OH or -CH3 groups on the polymer scaffold to tune the environment of active sites. Reaction rate measurements, spectroscopic techniques, along with DFT calculations show that HCP-OH catalysts enhance the hydrogenation rate of H-acceptor substrates containing carbonyl groups whereas hydrophobic HCP- CH3 ones promote non-H bond substrate activation. The functional groups go beyond enhancing substrate adsorption to partially activate the C = O bond and tune the catalytic sites. They also expose selectivity control in the hydrogenation of multifunctional substrates through preferential substrate functional group adsorption. The proposed synthetic strategy opens a new class of porous polymers for selective catalysis.

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Higher loadings of Pt single atoms and clusters over reducible metal oxides: application to C–O bond activation

Abstract: We develop higher loading of isolated noble metal atoms and clusters on a mildly reducible metal oxide. We demonstrated the approach for Pt supported on TiO2 and confirmed it by...

Cited by 9 publications

References 61 publications

Demonstrating the Electron–Proton-Transfer Mechanism of Aqueous Phase 4-Nitrophenol Hydrogenation Using Unbiased Electrochemical Cells

Demonstrating the Electron–Proton-Transfer Mechanism of Aqueous Phase 4-Nitrophenol Hydrogenation Using Unbiased Electrochemical Cells

Speciation of Nanocatalysts Using X-ray Absorption Spectroscopy Assisted by Machine Learning

Selective hydrogenation via precise hydrogen bond interactions on catalytic scaffolds

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