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Updated: Jun 26, 2026
Probing Surface Electrochemical Activity of Nanomaterials using a Hybrid Atomic Force Microscope-Scanning Electrochemical Microscope (AFM-SECM)
Published on: February 10, 2021
Electrolytically generated nanobubbles on highly orientated pyrolytic graphite surfaces.
Shangjiong Yang1, Peichun Tsai, E Stefan Kooij
1Physics of Fluids and Solid State Physics Groups, Faculty of Science and Technology, MESA+ Institute for Nanotechnology, University of Twente, 7500AE Enschede, The Netherlands.
This study explores how nanobubbles form on a type of graphite surface during water electrolysis. By applying voltage to the surface, hydrogen and oxygen nanobubbles are created. The researchers found that hydrogen nanobubbles form more often and in greater numbers than oxygen ones. As voltage increases, so does the size and number of nanobubbles, but they stop growing after about a minute, even though gas is still being produced. The study also shows that adding a small amount of salt increases the current but doesn’t change the basic behavior of the nanobubbles. The researchers suggest that gas either forms directly on the nanobubble surface or diffuses through it. These findings could help improve electrochemical processes by better understanding how nanobubbles behave.
Area of Science:
- Electrochemical nanotechnology
- Surface science in materials engineering
- Gas dynamics in electrochemistry
Background:
Electrochemical surface modification has been widely studied for its role in energy conversion and material science. Prior research has demonstrated that nanobubbles can form on electrode surfaces during electrolysis, but the mechanisms governing their formation and stability remain unclear. Established methods have shown that gas evolution occurs at electrode surfaces, but the dynamics of nanobubble growth and equilibrium have not been fully characterized. No prior work has resolved how voltage and electrolyte composition affect nanobubble yield and behavior. This gap motivated investigations into the relationship between electrolysis parameters and nanobubble formation on highly orientated pyrolytic graphite (HOPG). The need to understand nanobubble dynamics is driven by their potential applications in catalysis and energy storage. This paper contributes by examining the direct correlation between nanobubble volume growth and surface area during electrolysis. The study builds on existing electrochemical theory but introduces new insights into nanobubble stability and gas diffusion pathways.
Purpose Of The Study:
The aim of this study is to investigate the formation and growth dynamics of nanobubbles on HOPG surfaces during water electrolysis. The specific problem addressed is the lack of detailed understanding of how nanobubbles evolve under varying voltage and electrolyte conditions. The motivation stems from the potential of nanobubbles to enhance electrochemical processes through surface modification. The study seeks to clarify whether gas emerges directly at the nanobubble surface or diffuses through it. By correlating nanobubble growth with current measurements, the research aims to establish a model for nanobubble stability. The study also examines the impact of sodium chloride on electrolysis efficiency. The focus is on quantifying nanobubble yield and growth rates under controlled conditions. This work is intended to provide a foundation for future studies on nanobubble-based electrochemical systems.
Main Methods:
The study uses water electrolysis to generate nanobubbles on HOPG surfaces. The HOPG surface is used as a negative electrode for hydrogen nanobubbles and a positive electrode for oxygen nanobubbles. Atomic force microscopy (AFM) is employed to track nanobubble growth in real time. The total current during electrolysis is measured and correlated with AFM data. Voltage levels are systematically varied to assess their effect on nanobubble formation. The experiments are repeated with and without sodium chloride to evaluate its influence. Time-lapse measurements capture the growth and saturation of nanobubbles. The surface area and volume of nanobubbles are analyzed to determine growth patterns.
Main Results:
Hydrogen nanobubbles form more abundantly than oxygen nanobubbles during electrolysis on HOPG surfaces. The coverage and volume of nanobubbles increase with higher voltage. Nanobubble growth reaches a plateau after about 1 minute of electrolysis. The saturation of nanobubble size and current suggests a dynamic equilibrium. The surface area of nanobubbles correlates with growth rate, indicating gas emergence at the surface. The time constants of current and nanobubble aspect ratio remain consistent across conditions. Sodium chloride increases current magnitude but does not alter the qualitative behavior of nanobubbles. These findings suggest that gas diffusion through the nanobubble surface is a key factor in their stability.
Conclusions:
The authors propose that nanobubbles on HOPG surfaces reach a dynamic equilibrium after initial growth. They suggest that gas either emerges directly at the nanobubble surface or diffuses through it. The consistency of time constants and aspect ratios supports a stable growth model. The study confirms that hydrogen nanobubbles form more readily than oxygen nanobubbles. Sodium chloride enhances current but does not change the overall nanobubble behavior. The findings indicate that surface area and volume growth are closely related. The authors suggest that nanobubble formation is influenced by gas diffusion pathways. These conclusions are based on direct measurements and correlations between AFM data and current.
Frequently Asked Questions
The authors propose that gas either emerges directly at the nanobubble surface or diffuses through it, as indicated by the correlation between surface area and growth rate.
Sodium chloride increases current magnitude but does not qualitatively alter nanobubble behavior, suggesting it enhances conductivity without changing growth dynamics.
The authors suggest that nanobubbles reach a dynamic equilibrium, where gas production and diffusion balance, preventing further growth despite ongoing current.
AFM tracks nanobubble growth in real time, allowing correlation with current measurements to determine growth patterns and equilibrium states.
Hydrogen nanobubbles form in much larger quantities than oxygen nanobubbles, indicating a significant asymmetry in gas production under the same conditions.
The authors propose that consistent time constants and aspect ratios suggest a stable growth model governed by surface diffusion and equilibrium.
