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Related Concept Videos

π Electron Effects on Chemical Shift: Overview01:27

π Electron Effects on Chemical Shift: Overview

An applied magnetic field causes loosely bound π-electrons in organic molecules to circulate, producing a local or induced diamagnetic field over a large spatial volume. As the molecules tumble in solution, the field generated by π-electrons in spherical substituents results in a zero net field. However, the net field generated by π-electrons in non-spherical substituents is not zero. The effect of this induced field depends on the orientation of the molecule with respect to B0, resulting in...
π Electron Effects on Chemical Shift: Aromatic and Antiaromatic Compounds01:14

π Electron Effects on Chemical Shift: Aromatic and Antiaromatic Compounds

In aromatic compounds, such as benzene, the circulation of (4n + 2) π-electrons sets up a diamagnetic or diatropic ring current around the perimeter of the molecule. This current induces a magnetic field that opposes the external field inside the ring and reinforces it on the outside. The protons in benzene are deshielded and exhibit high chemical shifts in the range 6.5–8.5 ppm. The shielding effect at the center of the ring is evident in complex aromatic molecules, such as annulenes. In...
Inductive Effects on Chemical Shift: Overview01:27

Inductive Effects on Chemical Shift: Overview

The protons in unsubstituted alkanes are strongly shielded with chemical shifts below 1.8 ppm. Methine, methylene, and methyl protons appear at approximately 1.7, 1.2 and 0.7 ppm, while the proton signal from methane appears at 0.23 ppm. An electronegative substituent, such as chlorine, withdraws the electron density from the protons, increasing their chemical shift. Progressive substitution of the hydrogens in methane by chlorine shifts the proton signals increasingly downfield, to 3.05 ppm in...
Radical Reactivity: Steric Effects01:10

Radical Reactivity: Steric Effects

The presence of electron-donating, electron-withdrawing, or conjugating groups adjacent to a radical center, imparts electronic stabilization to the radicals. Examples of such electronically-stabilized radicals are triphenylmethyl, tetramethylpiperidine‐N‐oxide, and 2,2‐diphenyl‐1‐picrylhydrazyl. These radicals are remarkably stable and are known as persistent radicals. Some of the persistent radicals can even be isolated and purified.
Along with electronic factors, steric factors also account...
¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)01:20

¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)

When proton-coupled carbon-13 spectra are simplified by a broadband proton decoupling technique, structural information about the coupled protons is lost. Distortionless enhancement by polarization transfer (DEPT) is a technique that provides information on the number of hydrogens attached to each carbon in a molecule. While the DEPT experiment utilizes complex pulse sequences, the pulse delay and flip angle are specifically manipulated. The resulting signals have different phases depending on...
Stability of Conjugated Dienes01:28

Stability of Conjugated Dienes

Introduction
A comparison of the enthalpies of hydrogenation of dienes reveals that conjugated dienes release less heat on hydrogenation, rendering them more stable than their nonconjugated analogs.

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Applying Dynamic Strain on Thin Oxide Films Immobilized on a Pseudoelastic Nickel-Titanium Alloy
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Disentangling Electronic and Strain Effects in Core-Shell Pd@Pt Catalysts.

Qihao Li1, Zixiao Shi1, Michael Rebarchik2

  • 1Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States.

Journal of the American Chemical Society
|June 16, 2026
PubMed
Summary
This summary is machine-generated.

Researchers engineered palladium-platinum (Pd@Pt) core-shell nanocubes to boost electrocatalytic activity for hydrogen oxidation (HOR) and oxygen reduction (ORR). Electronic effects, not strain, significantly enhanced the platinum shell

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Synthesis and Testing of Supported Pt-Cu Solid Solution Nanoparticle Catalysts for Propane Dehydrogenation

Published on: July 18, 2017

Area of Science:

  • Electrocatalysis
  • Nanomaterials Science
  • Surface Chemistry

Background:

  • Enhancing intrinsic catalytic activity is crucial in electrocatalysis.
  • Nanoscale core-shell structures can improve catalytic activity and atom utilization.
  • Distinguishing strain effects from electronic interactions in core-shell catalysts is challenging.

Purpose of the Study:

  • To develop a Pd@Pt core-shell nanocube system to isolate and investigate electronic effects on electrocatalytic activity.
  • To quantify the catalytic enhancement for hydrogen oxidation (HOR) and oxygen reduction (ORR) reactions.
  • To elucidate the dominant mechanism (strain vs. electronic effects) responsible for altered catalytic properties.

Main Methods:

  • Synthesis of palladium-platinum (Pd@Pt) core-shell nanocubes.
  • Electrochemical evaluation of HOR and ORR activity under alkaline conditions.
  • X-ray photoelectron spectroscopy (XPS) for electronic structure analysis.
  • Density functional theory (DFT) calculations to model strain and electronic effects.

Main Results:

  • The Pd@Pt core-shell nanocubes showed over a 10-fold increase in catalytic activity for both HOR and ORR compared to pure platinum nanocubes.
  • XPS analysis indicated a downshift in the Pt d-band center, suggesting altered electronic properties.
  • DFT calculations confirmed that electronic effects, rather than lattice strain, were the primary contributors to the enhanced activity.
  • Weakened binding of reaction intermediates due to electronic effects was identified as the key factor.

Conclusions:

  • Electronic effects play a predominant role in enhancing the electrocatalytic activity of Pd@Pt core-shell nanocubes.
  • The Pd@Pt system effectively minimizes strain effects, allowing for clear attribution of performance gains to electronic modulation.
  • This study underscores the importance of understanding and controlling electronic interactions for designing high-performance electrocatalysts.