Observing Single‐Atom Catalytic Sites During Reactions with Electrospray Ionization Mass Spectrometry

Hülsey, Max J.; Sun, Geng; Sautet, Philippe; Yan, Ning

doi:10.1002/anie.202011632

Cited by 48 publications

(34 citation statements)

References 84 publications

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“…Previously, we reported similar catalysts to identify active sites during hydrogenation, as well as the CO and benzyl alcohol oxidation reactions. [13][14][15][16] Herein, we find a unique interplay between positively charged Pd and a reducible Mo-based support for hydrogen spillover. Due to the solubility of the SAC in polar solvents, techniques like electrospray ionisation mass spectrometry (ESI-MS), liquid phase 1 H NMR and UV-Vis spectroscopy become viable tools for the characterisation of the process.…”

Section: Introductionmentioning

confidence: 89%

“…1) while PW11O39 was synthesised following the procedure described in our previous study. 16 Mixing equimolar ratios of the lacunary POM and metal salts with weakly coordinating ligands yielded in situ the active site, PMo11O39Pd1, which can be easily and unambiguously characterised by 1a, b and Supplementary Fig. 2).…”

Section: Hydrogen Spillover On Pmo11o39pd1mentioning

confidence: 99%

“…SACs based on lacunary POMs offer advantages such as easy synthesis, stable structures in 1:1 metal support ratios, as well as their high solubility in polar solvents. 16 PMo11O39 was synthesised by the lithium carbonate-mediated removal of one MoO subunit from phosphomolybdic acid (Supplementary Fig. 1) while PW11O39 was synthesised following the procedure described in our previous study.…”

Section: Hydrogen Spillover On Pmo11o39pd1mentioning

confidence: 99%

“…The lacunary POMs were synthesised according to previously published procedures. 16 For K7PW11O39, in short, 18.15 g sodium tungstate dihydrate (SCR), 5 mL phosphoric acid (VWR, reagent grade) and 8.8 mL glacial acetic acid (Merck, reagent grade) dissolved in 30 mL deionised water and heated to reflux for 120 min. After the mixture was cooled down, 6 g potassium chloride (Sigma Aldrich, ACS reagent) were added, and the precipitation was continued for 60 min at room temperature.…”

Section: Catalyst Synthesismentioning

confidence: 99%

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Hydrogen spillover and its relation to catalysis: observations on structurally defined single-atom sites

Hülsey¹,

Fung²,

Yan³

2021

Preprint

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Hydrogen spillover, involving the transfer of H atoms from metal sites onto the catalyst support, is ubiquitous in chemical processes such as catalytic hydrogenation and hydrogen storage and is therefore of tremendous fundamental and technological interest. However, atomic level information concerning the kinetics of this process, the structural evolution of the catalysts during hydrogen spillover, as well as the nature of participation of the spilled over H in catalysis, remain vastly lacking. Here, we provide insights to those questions with the development of a solubilised polyoxometalate-supported single-atom catalyst which allows for the use of characterisation techniques generally inaccessible to study heterogeneous catalysis. Hydrogenation kinetics together with poisoning studies further reveal that hydrogen spillover can be either detrimental or beneficial for catalysis – the direction and magnitude of which depends predominantly on the nature of the reducible bond in the substrate. Similar trends were observed on one of the most prototypical hydrogen spillover catalysts, Pt/WO3, supporting the generalisability of the observations.

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Section: Introductionmentioning

confidence: 89%

Section: Hydrogen Spillover On Pmo11o39pd1mentioning

confidence: 99%

Section: Hydrogen Spillover On Pmo11o39pd1mentioning

confidence: 99%

Section: Catalyst Synthesismentioning

confidence: 99%

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Hydrogen spillover and its relation to catalysis: observations on structurally defined single-atom sites

Hülsey¹,

Fung²,

Yan³

2021

Preprint

Self Cite

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“…[106] Very recently, Yan and co-workers reported that POM-SACs can be used as gas-phase models to study reaction mechanisms, e.g., for CO and alcohol oxidation. [107] The group used high-resolution electrospray ionization mass spectrometry together with DFT calculations to explore mechanisms, reaction intermediates as well as kinetic and thermodynamic properties. The study demonstrates that the use of POM-SACs as model catalysts, together with combined cutting-edge experimental and theoretical methods lead to unprecedented levels of insight into complex reaction pathways.…”

Section: Gas-phase Catalysismentioning

confidence: 99%

Polyoxometalate‐Single Atom Catalysts (POM‐SACs) in Energy Research and Catalysis

Liu

Streb

2021

Advanced Energy Materials

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have only been explored since the early 21st century, mainly because their identification and characterization has been virtually impossible before, due to a lack of high-resolution instrumentation (such as electron or scanning probe microscopies). [1,4] Beyond classical heterogeneous SACs, much research has recently focused on developing molecular SAC model systems. Here, polyoxometalate-single atom catalysts (POM-SACs) are of enormous interest as these molecular metal oxides could form the link between molecularly well-defined prototypes and technologically relevant solid-state SACs. In this Review, we will provide a brief introduction into the current status in SACs chemistry. We then discuss pioneering studies as well as current research challenges in POM-SACs chemistry with an emphasis on sustainable energy research. Finally, we will identify future areas in POM-SAC research and highlight the bottlenecks which need to be overcome to further develop this field. Classical Single Atom Catalysts Common Anchoring Strategies and Applications of SACsSACs offer the ultimate atomic reactivity, as each single atom is interacting with its environment and can act as catalytic site. [7][8][9] The key to the successful preparation of SACs is to stabilize catalytic metal centers as individual atoms by utilizing hosts/supports featuring strong binding motifs (Figure 1). Early model systems included high specific surface area carbons, [10,11] metal oxides, [12,13] as well as materials with uniform pores and regular structures, such as zeolites, [14] metal organic frameworks (MOFs) [5,[14][15][16][17][18][19] and covalent organic frameworks (COFs). [20,21] Stabilization of single-atoms on supports requires a support-surface with specific anchoring sites, such as coordinatively unsaturated surface atoms (e.g., O 2− , OH − ), surface vacancies or heteroatom dopants (e.g., N, P, S, and halogens). The SACs can be stabilized on the support surface by covalent or ionic interactions, or by geometric enclosure in small pores. Each anchoring mode offers several benefits and challenges. For instance, the coordination of a single metal atom to surface oxo ligands makes the single-atom accessible from the outside, e.g., for binding of a substrate. However, it also leads to high surface-energy and destabilization of the single-atom, so that leaching, or agglomeration are possible. In contrast, Single atom catalysts-SACs-have received intense interest in sustainable energy research due to their enormous application potential and broad catalytic scope. In particular, SACs anchored on molecular metal oxides-polyoxometalates (POMs)-offer unrivalled possibilities as models to understand the function of these complex systems on the atomic level. Research questions which are difficult to address for classical heterogeneous SACs can be addressed by experiment and theory using POM-SACs as prototype catalysts. This review reviews the emerging field of POM-SAC research with a focus on fundamental properties and their application in energy conversion...

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Single‐Atom Fe Catalysts for Fenton‐Like Reactions: Roles of Different N Species

et al. 2022

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atoms in SACs are chemically bonded to elements on the supports. This unique structural characteristic endows SACs with strong metal support interactions (SMSIs) [6][7][8][9][10] and tailorable homogenized active metal sites. [11][12][13][14] SACs have been found to be very favorable in many fields, including electrocatalysis, [15][16][17][18] organocatalysis, [19][20][21] industrial catalysis, [22][23][24] and others. [25][26][27][28][29][30] Consequently, revealing the atomic structure of the central metal atoms and the SMSI in SACs has become an important subject of research because it provides possibilities for rational design of novel SACs for specific reactions. The recent development of advanced characterization techniques, including aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM), scanning tunneling microscopy images, extended X-ray absorption fine structure (EXAFS) curve fitting, and DFT modeling, provide crucial tools for identifying the atomic structure. [31][32][33][34][35][36][37] Meanwhile, tremendous efforts have been devoted to exploring SMSIs in SACs and their relationship with catalytic properties. [38][39][40][41] However, a systematic understanding of SMSIs Recognizing and controlling the structure-activity relationships of singleatom catalysts (SACs) is vital for manipulating their catalytic properties for various practical applications. Herein, Fe SACs supported on nitrogen-doped carbon (SA-Fe/CN) are reported, which show high catalytic reactivity (97% degradation of bisphenol A in only 5 min), high stability (80% of reactivity maintained after five runs), and wide pH suitability (working pH range 3-11) toward Fenton-like reactions. The roles of different N species in these reactions are further explored, both experimentally and theoretically. It is discovered that graphitic N is an adsorptive site for the target molecule, pyrrolic N coordinates with Fe(III) and plays a dominant role in the reaction, and pyridinic N, coordinated with Fe(II), is only a minor contributor to the reactivity of SA-Fe/CN. Density functional theory (DFT) calculations reveal that a lower d-band center location of pyrrolic-type Fe sites leads to the easy generation of Fe-oxo intermediates, and thus, excellent catalytic properties.

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Observing Single‐Atom Catalytic Sites During Reactions with Electrospray Ionization Mass Spectrometry

Cited by 48 publications

References 84 publications

Hydrogen spillover and its relation to catalysis: observations on structurally defined single-atom sites

Hydrogen spillover and its relation to catalysis: observations on structurally defined single-atom sites

Polyoxometalate‐Single Atom Catalysts (POM‐SACs) in Energy Research and Catalysis

Single‐Atom Fe Catalysts for Fenton‐Like Reactions: Roles of Different N Species

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