Comment on “Radical-mediated proton transfer enables hydroxyl radical formation in charge-delocalized water” by R. Zhao, Q. Zhang, N. Yang, L. Li, Z. Li and C. Cui, Chem. Sci. , 2025, 16 , 11954

Willem H. Koppenol

doi:10.1039/d5sc05396j

January 1, 2026Chemical ScienceOpen Access

Comment on “Radical-mediated proton transfer enables hydroxyl radical formation in charge-delocalized water” by R. Zhao, Q. Zhang, N. Yang, L. Li, Z. Li and C. Cui, Chem. Sci. , 2025, 16 , 11954

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Key Points

To critique the claims made by Cui and colleagues regarding the formation of hydroxyl radicals in low pH water.
Analyzed the thermodynamics of proton transfer processes.
Evaluated the conditions under which hydroxyl radicals might form.
Commented on the theoretical implications of charge-delocalized water and radical formation.
Challenged the spontaneous formation of hydroxyl radicals at pH below 4.
Demonstrated that proton transfer does not lead to the formation of hydroxyl radicals under claimed conditions.
Indicated that claims lack thermodynamic support.

Implication

This commentary challenges claims about hydroxyl radical formation in water at low pH, suggesting thermodynamic improbability.

Abstract

Cui and coworkers claim that H 2 O˙ + and HO˙ are formed spontaneously by lowering the pH to below 4. This is thermodynamically most unlikely. Thus, proton transfer does not involve HO˙.

Discussion

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Cite This Study

Willem H. Koppenol (2026) studied this question.

synapsesocial.com/papers/69d895be6c1944d70ce06d7b https://doi.org/10.1039/d5sc05396j

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Comment on “Radical-mediated proton transfer enables hydroxyl radical formation in charge-delocalized water” by R. Zhao, Q. Zhang, N. Yang, L. Li, Z. Li and C. Cui, Chem. Sci. , 2025, 16 , 11954

Key Points

Implication

Abstract

Discussion

Cite This Study

Comment on “Radical-mediated proton transfer enables hydroxyl radical formation in charge-delocalized water” by R. Zhao, Q. Zhang, N. Yang, L. Li, Z. Li and C. Cui, Chem. Sci. , 2025, 16 , 11954

Key Points

Implication

Abstract

Discussion

Cite This Study

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