M
 3,2-edge x-ray absorption near-edge structure spectroscopy: An alternative probe to the L3,2-edge near-edge structure for the unoccupied densities of d states of 5d metals

Sham, Tsun‐Kong; Naftel, S. J.; Coulthard, I.

doi:10.1063/1.361483

Cited by 48 publications

(47 citation statements)

References 11 publications

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“…To fully understand the effect of the unoccupied densities of 5 d states of the Pt catalysts, quantitative WL intensity analysis has been conducted on the basis of a reported method to determine the occupancy of the 5 d states in each sample384041 (see details in Methods). The Pt L 3 - and Pt L 2 -edge threshold and WL parameters were summarized in Table 1.…”

Section: Resultsmentioning

confidence: 99%

Platinum single-atom and cluster catalysis of the hydrogen evolution reaction

et al. 2016

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Platinum-based catalysts have been considered the most effective electrocatalysts for the hydrogen evolution reaction in water splitting. However, platinum utilization in these electrocatalysts is extremely low, as the active sites are only located on the surface of the catalyst particles. Downsizing catalyst nanoparticles to single atoms is highly desirable to maximize their efficiency by utilizing nearly all platinum atoms. Here we report on a practical synthesis method to produce isolated single platinum atoms and clusters using the atomic layer deposition technique. The single platinum atom catalysts are investigated for the hydrogen evolution reaction, where they exhibit significantly enhanced catalytic activity (up to 37 times) and high stability in comparison with the state-of-the-art commercial platinum/carbon catalysts. The X-ray absorption fine structure and density functional theory analyses indicate that the partially unoccupied density of states of the platinum atoms' 5d orbitals on the nitrogen-doped graphene are responsible for the excellent performance. S ecuring renewable and reliable sources of clean energy is one of the world's foremost challenges. Addressing this challenge is not only critical for the global economy but will also aid in the mitigation of environmental and health hazards caused by fossil fuels 1 . Hydrogen is the cleanest fuel available and is believed to be one of the most promising energy sources of the twenty-first century 2,3 . However, the majority of the hydrogen produced today is derived from steam-reformed methane, which is sourced from fossil reserves and produces a substantial amount of CO 2 (ref. 4). The production of hydrogen from water electrolysis is a promising alternative to the current CO 2 -emitting fossil fuel-based energy systems 5,6 .Platinum (Pt)-based catalysts are generally considered to be the most effective electrocatalysts for the hydrogen evolution reaction (HER) 5,7 . Unfortunately, Pt is expensive and scarce, limiting the commercial potential for such catalysts. The development of active, stable and inexpensive electrocatalysts for water splitting is a key step in the realization of a hydrogen economy, which is based on the use of molecular hydrogen for energy storage.Significant effort has been devoted to the search of non-preciousmetal-based HER catalysts, including sulfide-based materials 8-11 , and C 3 N 4 (refs 12-14). Although these candidate materials show promising activities for the HER, the activities of these catalysts in their present form are insufficient for industrial applications 15 .To overcome the challenges associated with the Pt HER catalysts and to drive the cost of H 2 production from water electrolysis down, it is very important to markedly decrease the Pt loading and increase the Pt utilization efficiency. Currently, supported Pt nanoparticles (NPs) are typically used to promote Pt activity towards the HER. Unfortunately, the geometry of the NPs limit the majority of the Pt atoms to the particle core, deeming them ineffect...

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Section: Resultsmentioning

confidence: 99%

Platinum single-atom and cluster catalysis of the hydrogen evolution reaction

et al. 2016

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“…The WL in Pt L 2 and L 3 edges arises from the dominant 2p 1/2 and 2p 3/2 transition to 5d 3/2 and 5d 5/2,3/2 , resectively (dipole selection rule: Δl = ±1, Δj = ±1, 0), indicating the presence of unoccupied densities of states of Pt 5d 5/2 and 5d 3/2 character in the samples. 57,58 The catalytic activity of Pt for various electrochemical reactions including ORR has been related to the density of states of employed Pt. 59,60 Furthermore, the interaction between the catalyst support and catalyst has been evaluated through study of the XANES spectrum.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

TiSi₂O_x Coated N-Doped Carbon Nanotubes as Pt Catalyst Support for the Oxygen Reduction Reaction in PEMFCs

et al. 2013

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Composite nanostrucutres of TiSi 2 O x coated nitrogen-doped carbon nanotubes (NCNTs) were synthesized by a combination of chemical vapor deposition (CVD) and magnetron sputtering processes. The synthesized nanostructures were used as supports for Pt catalyst for oxygen reduction reaction (ORR) in proton exchange memberane fuel cells (PEMFCs). An amorphous layer of TiSi 2 O x with controlled thicknesses was sputtered on NCNTs and followed by post-treatment at high temperature (1000°C, An-TiSi 2 O x -NCNTs), inducing TiO 2 nanoparticles of around 5 nm in diameter embedded in the amorphous layer. Further analyses via X-ray absorption spectroscopy of the Ti K edge and Si K edge revealed the Ti atoms were in a TiO 2 rutile environment and the Si atoms were in a SiO 2 environment. Pt nanoparticles with an average diameter of 3 nm were deposited on the composite support, and their electrochemical behaviors toward ORR were studied. It was revealed that, even with lower electrochemical surface area (ECSA), Pt/An-TiSi 2 O x -NCNTs showed better catalytic activity toward ORR than Pt/NCNT catalysts. The origin of enhanced activity of Pt/An-TiSi 2 O x -NCNTs was examined by high resolution transmission electron microscopy (HRTEM) and the X-ray absorption near edge structure spectra (XANES) of the deposited Pt nanoparticles.

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“…The multiple scattering resonance features up to 50 eV beyond the white-line are characteristic of the local environment of the absorbing Se atom. 58,59 Comparing Se K-edge XANES of the CdS x Se 1Àx nanostructures and with CdSe powder, there is a noticeable shift in the white-line to higher energy with increasing S content moving from CdSe (12661.2 eV) to yellow (12662.0 eV). 49 The binding energy of the Se increases from CdSe to yellow, when it is incorporated in a less favorable environment, such as a more CdS like wurtzite matrix.…”

Section: The Se K and L-edgementioning

confidence: 99%

Electronic structure and optical properties of CdSxSe1−x solid solution nanostructures from X-ray absorption near edge structure, X-ray excited optical luminescence, and density functional theory investigations

Murphy

Yiu

Ward

et al. 2014

Journal of Applied Physics

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Articles you may be interested in Ca K-edge X-ray absorption fine structure in BaTiO3-CaTiO3 solid solutions J. Appl. Phys. 113, 044106 (2013); 10.1063/1.4784226 In situ near-edge x-ray absorption fine structure spectroscopy investigation of the thermal defunctionalization of graphene oxide J. The electronic structure and optical properties of a series of iso-electronic and iso-structural CdS x Se 1Àx solid solution nanostructures have been investigated using X-ray absorption near edge structure, extended X-ray absorption fine structure, and X-ray excited optical luminescence at various absorption edges of Cd, S, and Se. It is found that the system exhibits compositions, with variable local structure in-between that of CdS and CdSe accompanied by tunable optical band gap between that of CdS and CdSe. Theoretical calculation using density functional theory has been carried out to elucidate the observations. It is also found that luminescence induced by X-ray excitation shows new optical channels not observed previously with laser excitation. The implications of these observations are discussed. V C 2014 AIP Publishing LLC.

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M 3,2-edge x-ray absorption near-edge structure spectroscopy: An alternative probe to the L3,2-edge near-edge structure for the unoccupied densities of d states of 5d metals

Cited by 48 publications

References 11 publications

Platinum single-atom and cluster catalysis of the hydrogen evolution reaction

Platinum single-atom and cluster catalysis of the hydrogen evolution reaction

TiSi₂O_x Coated N-Doped Carbon Nanotubes as Pt Catalyst Support for the Oxygen Reduction Reaction in PEMFCs

Electronic structure and optical properties of CdSxSe1−x solid solution nanostructures from X-ray absorption near edge structure, X-ray excited optical luminescence, and density functional theory investigations

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M 3,2-edge x-ray absorption near-edge structure spectroscopy: An alternative probe to the L3,2-edge near-edge structure for the unoccupied densities of d states of 5d metals

Cited by 48 publications

References 11 publications

Platinum single-atom and cluster catalysis of the hydrogen evolution reaction

Platinum single-atom and cluster catalysis of the hydrogen evolution reaction

TiSi2Ox Coated N-Doped Carbon Nanotubes as Pt Catalyst Support for the Oxygen Reduction Reaction in PEMFCs

Electronic structure and optical properties of CdSxSe1−x solid solution nanostructures from X-ray absorption near edge structure, X-ray excited optical luminescence, and density functional theory investigations

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TiSi₂O_x Coated N-Doped Carbon Nanotubes as Pt Catalyst Support for the Oxygen Reduction Reaction in PEMFCs