Understanding the Role of Surface Heterogeneities in Electrosynthesis Reactions

Carvalho, O. Quinn; Adiga, Prajwal; Murthy, Sri Krishna; Fulton, John L.; Gutiérrez, Oliver Y.; Stoerzinger, Kelsey A.

doi:10.1016/j.isci.2020.101814

Cited by 19 publications

(11 citation statements)

References 75 publications

(77 reference statements)

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“…Spectroscopy, particularly microspectroscopy, is an important tool for mapping heterogeneity in electrocatalyst activity and selectivity. 7 The high molecular sensitivity and (sub)monolayer detection limits of surface sensitive infrared methods make them particularly powerful for in situ studies of electroactive interfaces. Attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) is well suited for studying electrocatalysis reactions due to the generation of highly localized electric fields around metal nanoparticles leading to excellent surface sensitivity and a lack of interference from the bulk electrolyte.…”

Section: Introductionmentioning

confidence: 99%

Probing Heterogeneity in Attenuated Total Reflection Surface-Enhanced Infrared Absorption Spectroscopy (ATR-SEIRAS) Response with Synchrotron Infrared Microspectroscopy

Morhart

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et al. 2021

Appl Spectrosc

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The heterogeneity of metal island films electrodeposited on conductive metal oxide modified internal reflection elements is shown to provide a variable ATR-SEIRAS (attenuated total reflection surface enhanced infrared absorption spectroscopy) response. A self-assembled monolayer of a ferrocene-terminated thiol monolayer (FcC11SH) was formed on the gold islands covering a single substrate, which was measured using both a conventional spectrometer and a custom-built horizontal microscope. Cyclic voltammetry and ATR-SEIRAS results reveal that the FcC11SH modified substrate undergoes a reversible electron transfer and an associated re-orientation of both the ferrocene/ferrocenium headgroup and the hydrocarbon backbone. The magnitude of the absorption signal arising from the redox changes in the monolayer, as well as the IR signature arising from the ingress/egress of the perchlorate counterions, is shown to depend significantly on the size of the infrared beam spot when using a conventional FTIR spectrometer. By performing equivalent measurements on a horizontal microscope, the primary cause of the differences in the signal level is found to be the hetereogeneity in the density of gold islands on the conductive metal oxide.

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Section: Introductionmentioning

confidence: 99%

Probing Heterogeneity in Attenuated Total Reflection Surface-Enhanced Infrared Absorption Spectroscopy (ATR-SEIRAS) Response with Synchrotron Infrared Microspectroscopy

Morhart

Read

et al. 2021

Appl Spectrosc

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“…At potentials where H ads is present on an electrocatalyst surface, organics in solution can be reduced via reaction with such species (Hadd in Figure 2A) and/or via proton-coupled-electron-transfer steps (PCET in Figure 2A). 42 The possibility for catalyst hydride formation resulting from H ads incorporation in the lattice as H abs should also be considered for sufficiently cathodic potentials; however, the presence of the organic (and associated ECH kinetics) can also influence hydride formation. For example, Pd forms β-PdH x at potentials around −0.1 V RHE when driving HER and ECH of phenol but forms only an α-PdH x (<1.7% H, Figure 1A) during ECH of benzaldehyde.…”

Section: Electrocatalytic Hydrogenationmentioning

confidence: 99%

Role of Hydride Formation in Electrocatalysis for Sustainable Chemical Transformations

Padavala

Stoerzinger

2023

ACS Catal.

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The electrochemical potential of numerous reduction reactions corresponds to hydrogen pressures that thermodynamically favor the formation of many metal hydrides. Whether a catalyst remains metallic with hydrogen on the surface (Hads) or absorbs hydrogen into its lattice (Habs), forming a metal hydride, results from a balance between not only this thermodynamic driving force but also the kinetics of concurrent surface reactions and equilibrium surface coverage. Drawing parallels with thermal catalytic processes, we provide examples of how hydride formation impacts electrocatalysis in H2 evolution, organic and CO2 reduction, and N2 and NO3 – reduction reactions. Hydride formation not only changes catalyst activity and selectivity but also can impact durability. We highlight techniques capable of identifying hydride formation under reaction conditions, imperative for an understanding of electrocatalyst kinetics. Hydrides offer many possibilities in electrocatalysis, including unique reaction mechanisms involving the catalyst lattice and innovative reactor architectures, beneficial for applications in chemical transformations and energy.

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“…[89,90] Under sufficiently cathodic potentials, CeO2-δ is known to form 𝑣 𝑂 •• , [37] stabilizing the adsorption of oxidizers such as nitrate and electrosynthetic oxygen redox reactions. [91] NO3RR FE (Figure 8a) at less-cathodic applied potentials (-0. 5d) and is in line with speciation measurements in low nitrate concentrations (Figure 7b).…”

Section: Role Of Support Structure On No3rr Selectivity At High Conce...mentioning

confidence: 99%

Role of oxide support in electrocatalytic nitrate reduction on Cu

Carvalho

Jones

Berninghaus

et al. 2022

Electrochemical Science Adv

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The electrochemical nitrate reduction reaction (NO3RR) has the potential for distributed water treatment and renewable chemical synthesis. Cu is an active monometallic electrocatalyst for the NO3RR in acidic and alkaline electrolytes, where activity is limited by reduction of adsorbed nitrate to nitrite. Oxygen-vacancy forming metal-oxide supports provide sites for N-O bond activation in thermal reduction, impacting product distribution as well. Here we compare the electrochemical NO3RR activity of Cu deposited on two metaloxide supports (cerium dioxide [Cu/CeO2-δ] and fluorine-doped tin dioxide [Cu/FTO]) to a Cu foil benchmark. Considering activity in phosphate-buffered neutral media, nitrate and adsorbed hydrogen compete for surface sites under NO3RR conditions. The less-cathodic overpotential on Cu/CeO2-δ compared to Cu/FTO is attributed to stronger nitrate adsorption, similar to thermal nitrate reduction. Utilization of CeO2-δ as electrocatalyst support slightly shift product distribution towards more oxidized products, either by enhancing nitrate affinity or by a more dynamic process involving formation and healing of oxygen vacancies (𝑣 𝑂 •• ).These results suggest supporting catalysts on metal-oxides may enhance activity by promoting adsorption of anionic reactants on cathodic electrocatalysts.

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Understanding the Role of Surface Heterogeneities in Electrosynthesis Reactions

Cited by 19 publications

References 75 publications

Probing Heterogeneity in Attenuated Total Reflection Surface-Enhanced Infrared Absorption Spectroscopy (ATR-SEIRAS) Response with Synchrotron Infrared Microspectroscopy

Probing Heterogeneity in Attenuated Total Reflection Surface-Enhanced Infrared Absorption Spectroscopy (ATR-SEIRAS) Response with Synchrotron Infrared Microspectroscopy

Role of Hydride Formation in Electrocatalysis for Sustainable Chemical Transformations

Role of oxide support in electrocatalytic nitrate reduction on Cu

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