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Redox Equilibria: Overview01:23

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A reduction-oxidation reaction is commonly called a redox reaction. In a redox reaction, electrons are transferred from one species to another rather than being shared between or among atoms. The reducing agent or reductant is the species that loses electrons and gets oxidized in the process. The species that gains electrons and gets reduced in the process is the oxidizing agent or oxidant. Redox reactions are represented as two separate equations called half-reactions, where one equation...
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Reaction Kinetics and Combustion Dynamics of I4O9 and Aluminum Mixtures
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Published on: November 7, 2016

Oxidized-State Accumulation Controls Water Oxidation Kinetics on a Model Iridium Atomic Array.

Yang Li1,2, Guoxiang Zhao3, Chen Zou1

  • 1Center For Renewable Energy and Storage Technologies (CREST), Physical Science and Engineering Division, King Abdullah University of Science and Technology, Thuwal, Kingdom of Saudi Arabia.

Angewandte Chemie (International Ed. in English)
|May 7, 2026
PubMed
Summary
This summary is machine-generated.

This study reveals how applied bias and a cerium oxide support enhance iridium catalysts for water oxidation. This improves renewable energy conversion by optimizing charge accumulation and catalyst stability.

Keywords:
PEMWEhydrogen evolutioniridium atom arraysoxidized‐state accumulationwater oxidation kinetics

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Area of Science:

  • Materials Science
  • Electrochemistry
  • Catalysis

Background:

  • Water oxidation is crucial for renewable energy but kinetically complex.
  • Tafel analyses often fail to capture the interplay of electron transfer and proton-involved steps.

Purpose of the Study:

  • To elucidate the molecular-scale kinetics mechanism of water oxidation.
  • To investigate the role of applied bias and support material on catalyst performance and stability.

Main Methods:

  • Design of cerium dioxide nanorod-supported iridium atomic arrays (Ir/CeO2) as a model catalyst.
  • Analysis of charge accumulation and its effect on reaction kinetics.
  • Evaluation of catalyst activity and durability in proton exchange membrane water electrolyzers.

Main Results:

  • Applied bias regulates current via oxidative charge accumulation, reducing activation energy for OOH formation.
  • The CeO2 support prevents iridium over-oxidation and dissolution, enhancing stability.
  • The Ir/CeO2 catalyst achieves industrial-level current densities at low cell voltages with superior activity and durability.

Conclusions:

  • Charge accumulation, not direct action on the reaction coordinate, is key to enhanced water oxidation kinetics.
  • The electron-buffering capacity of the CeO2 support is vital for catalyst stability.
  • Molecular insights into charge-controlled kinetics highlight the importance of chemical steps in multi-electron reactions.