Intrabubble coupled evolution of microdroplets and nanobubbles in oxygen evolution reaction.

Authors

Congfan Zhao, Shu Yuan, Jiabin You, Chenyun Bai, Yongjian Su, Xiaojing Cheng, Shuiyun Shen, Xiaohui Yan, Junliang Zhang

Published in

Proceedings of the National Academy of Sciences of the United States of America. Volume 123. Issue 27. Pages e2606452123. Jul 07, 2026. Epub Jul 01, 2026.

Abstract

In the oxygen evolution reaction (OER), adherent gas bubbles are conventionally viewed as a major impediment that blocks ion and mass transport by covering active sites. Here, we show that for ionomer-based electrodes, this prevailing view is oversimplified. Using a self-developed transparent on-chip electrolyzer that integrates multimodal in-situ characterization, including optical microscopy, spectroscopic analysis, and atomic force microscopy, we uncover complex intrabubble dynamics on ionomer-coated electrodes. During bubble growth, the three-phase contact line exhibits characteristic pinning-depinning behavior. Beyond a critical bubble size (~420 μm), free water molecules are evolved from the ionomer into the bubble-electrode contact area, forming microdroplets (<20 μm) that continuously coalesce. Inside these microdroplets, oxygen products further nucleate as pancake-shaped nanobubbles (~50 nm), revealing a previously unrecognized intrabubble process. We find that this coupled microdroplet-nanobubble evolution is enabled by the phase-separation behavior of ionomer. The ionomer also preserves local electrochemical activity even under substantial bubble coverage, unlike ionomer-free electrodes where bubble blockage leads to severe deactivation. By tailoring ionomer phase separation, we achieve intensified microdroplet-nanobubble evolution and measurable performance improvement at high current densities. This finding opens a route to mitigate bubble-induced activity loss in OER electrodes.

PMID:
42384694
Bibliographic data and abstract were imported from PubMed on 02 Jul 2026.

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