Electrochemical CO Oxidation at Platinum on Carbon Studied through Analysis of Anomalous in Situ IR Spectra

McPherson, Ian J.; Ash, Philip A.; Jones, Lewys; Varambhia, Aakash; Jacobs, Robert M.; Vincent, Kylie A.

doi:10.1021/acs.jpcc.7b02166

Cited by 60 publications

(60 citation statements)

References 87 publications

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“…Meanwhile, for CO electro-oxidation, surface atoms with orange color are mainly located at edges and {100} terraces, while surface atoms with blue color appear in bottom of steps and several protruded corners. These geometric features are consistent with the previous experimental results, demonstrating that different morphologies of catalysts lead to different catalytic activities [48][49][50][51][52] . Compared to fcc model structures, the reduced size of {111} and {100}-facets of the synthesized Pt nanocrystals results in a lowering of CN .…”

Section: Resultssupporting

confidence: 91%

Correlating 3D Surface Atomic Structure and Catalytic Activities of Pt Nanocrystals

et al. 2021

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Active sites and catalytic activity of heterogeneous catalysts is determined by their surface atomic structures. However, probing surface structure at atomic resolution is difficult especially for solution ensembles of catalytic nanocrystals which consist of heterogeneous particles with irregular shapes and surfaces. Here, we constructed 3D maps of coordination number (CN) and generalized CN ( CN ) for individual surface atoms of sub-3 nm Pt nanocrystals. Our results reveal that the synthesized Pt nanocrystals are enclosed by islands of atoms with non-uniform shapes that lead to complex surface structures, including a high ratio of low-coordination surface atoms, reduced domain size of low-index facets, and various types of exposed high-index facets. 3D maps of CN are directly correlated to catalytic activities assigned to individual surface atoms with distinct local coordination structures, which explains the origin of high catalytic performance of small Pt nanocrystals in important reactions such as oxygen reduction reaction and CO electro-oxidation.

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Section: Resultssupporting

confidence: 91%

Correlating 3D Surface Atomic Structure and Catalytic Activities of Pt Nanocrystals

et al. 2021

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“… 40 , 47 , 51 , 52 , 54 , 56 − 58 The pronounced bipolar shape of the atop CO feature has been commonly observed for infrared reflectance measurements of CO adsorbed on carbon-supported metal nanoparticles and has been ascribed to optical effects. 57 , 59 − 62 As the pH is increased to 7 ( Figure 3 a, black) and 9 ( Figure 3 a, blue), ν(CO A ) redshifts to 2041 and 2035 cm –1 , respectively. Importantly, since the bipolar peak shape is preserved across the pH range investigated, this optical artifact would minimally convolute the extracted trends in peak position.…”

Section: Resultsmentioning

confidence: 99%

Spontaneous Electric Fields Play a Key Role in Thermochemical Catalysis at Metal−Liquid Interfaces

2021

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Large oriented electric fields spontaneously arise at all solid–liquid interfaces via the exchange of ions and/or electrons with the solution. Although intrinsic electric fields are known to play an important role in molecular and biological catalysis, the role of spontaneous polarization in heterogeneous thermocatalysis remains unclear because the catalysts employed are typically disconnected from an external circuit, which makes it difficult to monitor or control the degree of electrical polarization of the surface. Here, we address this knowledge gap by developing general methods for wirelessly monitoring and controlling spontaneous electrical polarization at conductive catalysts dispersed in liquid media. By combining electrochemical and spectroscopic measurements, we demonstrate that proton and electron transfer from solution controllably, spontaneously, and wirelessly polarize Pt surfaces during thermochemical catalysis. We employ liquid-phase ethylene hydrogenation on a Pt/C catalyst as a thermochemical probe reaction and observe that the rate of this nonpolar hydrogenation reaction is significantly influenced by spontaneous electric fields generated by both interfacial proton transfer in water and interfacial electron transfer from organometallic redox buffers in a polar aprotic ortho -difluorobenzene solvent. Across these vastly disparate reaction media, we observe quantitatively similar scaling of ethylene hydrogenation rates with the Pt open-circuit electrochemical potential ( E OCP ). These results isolate the role of interfacial electrostatic effects from medium-specific chemical interactions and establish that spontaneous interfacial electric fields play a critical role in liquid-phase heterogeneous catalysis. Consequently, E OCP —a generally overlooked parameter in heterogeneous catalysis—warrants consideration in mechanistic studies of thermochemical reactions at solid–liquid interfaces, alongside chemical factors such as temperature, reactant activities, and catalyst structure. Indeed, this work establishes the experimental and conceptual foundation for harnessing electric fields to both elucidate surface chemistry and manipulate preparative thermochemical catalysis.

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“…[59] One plausible explanation for the deficit of charge could be CO adsorption/poisoning or CO oxidation taking place at the platinum counter electrode, [64] or alternatively the hexafluorophosphate anion or acetonitrile may be oxidized.F inally,t he products of Hofmann degradation of tetrabutylammonium( tributylamine, butene, and bicarbonate) were also not detected by GC analysis (see Figures S33-S42 in the SupportingI nformation), suggesting that theses peciesa re unstable during prolonged electrolysis in CXEs. In such ap athway,f erroceneo xidized at the counter electrode (anode) could migrate to the working electrode (cathode) and be promptly reducedu nder electrocatalytic conditions.…”

Section: àmentioning

confidence: 99%

Intensified Electrocatalytic CO₂ Conversion in Pressure‐Tunable CO₂‐Expanded Electrolytes

et al. 2019

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Multimolar CO2 concentrations are achieved in acetonitrile solutions containing supporting electrolyte at relatively mild CO2 pressures (<5 MPa) and ambient temperature. Such CO2‐rich, electrolyte‐containing solutions are termed as CO2‐eXpanded Electrolytes (CXEs) because significant volumetric expansion of the liquid phase accompanies CO2 dissolution. Cathodic polarization of a model polycrystalline gold electrode‐catalyst in CXE media enhances CO2 to CO conversion rates by up to an order of magnitude compared with those attainable at near‐ambient pressures, without loss of selectivity. The observed catalytic process intensification stems primarily from markedly increased CO2 availability. However, a non‐monotonic correlation between the dissolved CO2 concentration and catalytic activity is observed, with an optimum occurring at approximately 5 m CO2 concentration. At the highest applied CO2 pressures, catalysis is significantly attenuated despite higher CO2 concentrations and improved mass‐transport characteristics, attributed in part to increased solution resistance. These results reveal that pressure‐tunable CXE media can significantly intensify CO2 reduction rates over known electrocatalysts by alleviating substrate starvation, with CO2 pressure as a crucial variable for optimizing the efficiency of electrocatalytic CO2 conversion.

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Electrochemical CO Oxidation at Platinum on Carbon Studied through Analysis of Anomalous in Situ IR Spectra

Cited by 60 publications

References 87 publications

Correlating 3D Surface Atomic Structure and Catalytic Activities of Pt Nanocrystals

Correlating 3D Surface Atomic Structure and Catalytic Activities of Pt Nanocrystals

Spontaneous Electric Fields Play a Key Role in Thermochemical Catalysis at Metal−Liquid Interfaces

Intensified Electrocatalytic CO₂ Conversion in Pressure‐Tunable CO₂‐Expanded Electrolytes

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Electrochemical CO Oxidation at Platinum on Carbon Studied through Analysis of Anomalous in Situ IR Spectra

Cited by 60 publications

References 87 publications

Correlating 3D Surface Atomic Structure and Catalytic Activities of Pt Nanocrystals

Correlating 3D Surface Atomic Structure and Catalytic Activities of Pt Nanocrystals

Spontaneous Electric Fields Play a Key Role in Thermochemical Catalysis at Metal−Liquid Interfaces

Intensified Electrocatalytic CO2 Conversion in Pressure‐Tunable CO2‐Expanded Electrolytes

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Intensified Electrocatalytic CO₂ Conversion in Pressure‐Tunable CO₂‐Expanded Electrolytes