Enhancing hot electron collection with nanotube-based three-dimensional catalytic nanodiode under hydrogen oxidation

Goddeti, Kalyan C.; Lee, Hyosun; Jeon, Beomjoon; Park, Jeong Young

doi:10.1039/c8cc04288h

Cited by 13 publications

(18 citation statements)

References 33 publications

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“…The rate of formation of thermal electrons by reaction follows the Arrhenius relationship; therefore, as in the catalyst performance, an exponential relationship with temperature rise is shown. An electrical potential-free system allows for the observation of hot electrons across the initial Schottky barrier ( E SB,0 ). ,, A net chemicurrent ( I ch ) can be calculated by excluding the thermoelectric current obtained under pure O 2 (760 Torr) conditions from a total current obtained under catalytic reaction conditions (Figure a).…”

Section: Results and Discussionmentioning

confidence: 99%

“…Here, Park and Somorjai designed a Schottky nanodiode composed of metal–semiconductor for collecting hot electrons upon chemical reaction . Originating from the energy dissipation during the catalytic reaction, steady-state hot electron flow, termed “chemicurrent”, can be detected through an electrical circuit. − This chemicurrent study is highly associated with surface and interfaces at the nanoscale, which is dependent on the inherent properties of each material, like metal or semiconductors, and demonstrated by the differential trapping of electrons. , Recently, hot electron detection has been conducted for three-dimensional Schottky nanodiodes, demonstrating that hot electrons can be generated in practical metal–semiconductor catalysts based on nanotubular or mesoporous support oxide and can also be efficiently collected when an electrical circuit is established. − …”

Section: Introductionmentioning

confidence: 99%

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Electronic Control of Hot Electron Transport Using Modified Schottky Barriers in Metal–Semiconductor Nanodiodes

Jeon

Lee

Park

2021

ACS Appl. Mater. Interfaces

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Hot electron flux, generated by both incident light energy and the heat of the catalytic reaction, is a major element for energy conversion at the surface. Controlling hot electron flux in a reversible manner is extremely important for achieving high energy conversion efficiency. Here we demonstrate that hot electron flux can be controlled by tuning the Schottky barrier height. This phenomenon was monitored by using a Schottky nanodiode composed of a metal−semiconductor. The formation of a Schottky barrier at a nanometer scale inevitably accompanies an intrinsic image potential between the metal−semiconductor junction, which lowers the effective Schottky barrier height. When a reverse bias is applied to the nanodiode, an additional image potential participates in a secondary barrier lowering, leading to the increased hot electron flow. Besides, a decrease of tunneling width results in facile electron transport through the barrier. The increased hot electron flux by the chemical reaction (chemicurrent) and by the photon absorption (photocurrent) indicates hot electrons are captured more effectively by modifying the Schottky barrier. This study can shed light on a quantitative understanding and application of charge behavior at metal−semiconductor interfaces, in solar energy conversion, or in a catalytic reaction.

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Section: Results and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Electronic Control of Hot Electron Transport Using Modified Schottky Barriers in Metal–Semiconductor Nanodiodes

Jeon

Lee

Park

2021

ACS Appl. Mater. Interfaces

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“…18 Recently, a three-dimensional catalytic nanodiode composed of Pt on TiO 2 nanotubes was fabricated for efficient detection of hot electrons. 19 We also demonstrated the detection of hot electrons measured at the solid−liquid interface during the catalytic decomposition of aqueous hydrogen peroxide on Ag or Pt/n-Si Schottky nanodiodes. 20 In contrast with a one-path reaction (e.g., oxidation of CO or hydrogen), the study of selectivity is an important issue for predominantly obtaining the desired product from a multipath reaction in heterogeneous catalysis.…”

Section: Introductionmentioning

confidence: 93%

“…Park and co-workers reported the detection of hot electrons as a steady-state current created during more complex surface reactions (in this instance, CO oxidation and hydrogen oxidation) using various Schottky diodes and found a clear relationship between turnover rate and hot electron flow. − In a previous study on Pt nanoparticles on Au/TiO 2 catalytic nanodiodes, we showed that hot electron generation was higher with smaller Pt nanoparticles, which is related to the short travel distance for the hot electrons compared with their inelastic mean free path . Recently, a three-dimensional catalytic nanodiode composed of Pt on TiO 2 nanotubes was fabricated for efficient detection of hot electrons . We also demonstrated the detection of hot electrons measured at the solid–liquid interface during the catalytic decomposition of aqueous hydrogen peroxide on Ag or Pt/n-Si Schottky nanodiodes …”

Section: Introductionmentioning

confidence: 96%

Intrinsic Relation between Hot Electron Flux and Catalytic Selectivity during Methanol Oxidation

et al. 2019

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Catalytic selectivity, or the production of only one desired molecule that may be used as a fuel or chemical out of several thermodynamically possible molecules, is the foundation of surface chemistry. During catalytic reactions, electronic excitation taking place on the surface creates energetic electrons called “hot electrons” that have a significant impact on catalytic reactions. Despite its importance in fundamentally understanding electronic excitation on the surface, no reports show the relation between hot electron flow and catalytic selectivity. Here, using a Pt/n-type TiO2 Schottky nanodiode, we show the intrinsic relation between hot electron flow and catalytic selectivity. On the Pt thin film, hot electron flow was generated by methanol oxidation exhibiting a two-path reaction of either full oxidation to CO2 or partial oxidation to methyl formate; a steady-state chemicurrent was detected. We show that the activation energy of the chemicurrent is quite close to that of the turnover frequency, indicating that the chemicurrent originated from the catalytic reaction on the Pt thin film. The dependence of the chemicurrent on methanol partial pressure was investigated by varying the partial pressure of methanol (1–4 Torr). We show that hot electron generation is more effective in the reaction pathway that produces methyl formate. On the basis of these results, we conclude that the selectivity for methyl formate production correlates well with hot electron generation because of the higher exothermicity of generating the intermediate, as was confirmed using theoretical calculations based on the density functional theory.

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“…Thus, the effect of Schottky barrier height on the hot electron detection can be excluded by showing a similar Schottky barrier to that of the Pt film (i.e., about 0.87 and 0.85 eV for Pt film/TiO 2 and Pt nanowires/TiO 2 , respectively). Recently, the detection of excited hot electrons as a steady-state chemicurrent under the catalytic oxidation of CO or hydrogen was demonstrated by using metal catalyst/TiO 2 Schottky nanodiodes and a clear correlation was found between catalytic activity and reaction-induced hot electron flux 10,[37][38][39][40][41] . In this study, the chemically excited hot electrons generated by methanol oxidation were enough to irreversibly overcome the Schottky barrier at the Pt nanowire arrays/TiO 2 junction when the excess chemical energy was higher than the Schottky barrier height of the nanodiode (i.e., obtained sufficient energy) and could be detected as a current of hot electron flow.…”

Section: Detection Of Hot Electrons On Pt Nanowires/tio 2 Nanodiodesmentioning

confidence: 99%

Controlling hot electron flux and catalytic selectivity with nanoscale metal-oxide interfaces

et al. 2021

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Interaction between metal and oxides is an important molecular-level factor that influences the selectivity of a desirable reaction. Therefore, designing a heterogeneous catalyst where metal-oxide interfaces are well-formed is important for understanding selectivity and surface electronic excitation at the interface. Here, we utilized a nanoscale catalytic Schottky diode from Pt nanowire arrays on TiO2 that forms a nanoscale Pt-TiO2 interface to determine the influence of the metal-oxide interface on catalytic selectivity, thereby affecting hot electron excitation; this demonstrated the real-time detection of hot electron flow generated under an exothermic methanol oxidation reaction. The selectivity to methyl formate and hot electron generation was obtained on nanoscale Pt nanowires/TiO2, which exhibited ~2 times higher partial oxidation selectivity and ~3 times higher chemicurrent yield compared to a diode based on Pt film. By utilizing various Pt/TiO2 nanostructures, we found that the ratio of interface to metal sites significantly affects the selectivity, thereby enhancing chemicurrent yield in methanol oxidation. Density function theory (DFT) calculations show that formation of the Pt-TiO2 interface showed that selectivity to methyl formate formation was much larger in Pt nanowire arrays than in Pt films because of the different reaction mechanism.

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Enhancing hot electron collection with nanotube-based three-dimensional catalytic nanodiode under hydrogen oxidation

Cited by 13 publications

References 33 publications

Electronic Control of Hot Electron Transport Using Modified Schottky Barriers in Metal–Semiconductor Nanodiodes

Electronic Control of Hot Electron Transport Using Modified Schottky Barriers in Metal–Semiconductor Nanodiodes

Intrinsic Relation between Hot Electron Flux and Catalytic Selectivity during Methanol Oxidation

Controlling hot electron flux and catalytic selectivity with nanoscale metal-oxide interfaces

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