BUBBLE-AFM : Molecular processes at electrode/electrolyte interfaces during water electrolysis : from solvent restructuring to nanobubble nucleation
Description of the PhD project
The transition toward sustainable energy systems critically relies on the development of efficient water electrolysis technologies for green hydrogen production. However, the performance of electrolyzers is strongly limited by the formation, growth, and adhesion of gas bubbles at electrode surfaces, which block active sites, increase local resistance, and alter mass transport near the interface. Despite extensive studies, the fundamental mechanisms governing the earliest stages of bubble nucleation, occurring at the nanometric scale, remain poorly understood due to the lack of suitable in situ characterization techniques.
This PhD proposal aims to address this major knowledge gap by developing an innovative experimental approach combining electrochemical control with in situ Atomic Force Microscopy (AFM) in liquid environments. Building on recent advances and the installation of a new electrochemical AFM platform within the ESPCI premises, the project will provide unprecedented access to molecular-scale processes occurring at electrode/electrolyte interfaces during water electrolysis. In particular, it seeks to elucidate the transition from solvent restructuring under applied potential to gas supersaturation and ultimately nanobubble nucleation (Fig. A).
The scientific rationale rests on the hypothesis that bubble nucleation is a metastable process governed by a subtle interplay between local surface properties (chemistry, wettability, roughness, defects) and electrochemical conditions. To get novel fundamental insights into this process, we will first focus on model electrodes (e.g., graphite). We will rely on high-speed and high-resolution dynamic force spectroscopy of near-surface structural and solvation forces (Figs. C-D), which will provide insight into the early stages of bubble nucleation — from solvent restructuring under electrochemical potential, to interfacial gas saturation, to bubble nucleation and growth kinetics (Fig. A). We will then extend our investigations towards more realistic electrodes, using high-resolution imaging of surface nanobubbles (Fig. E) to correlate local bubble nucleation with surface chemistry (hydrophilicity/hydrophobicity balance), topography, and defects. Together, these measurements will help identify nucleation pathways and clarify the role of surface heterogeneities in triggering bubble formation.
A second objective will then be to establish quantitative correlations between these nanoscale observations and macroscopic electrochemical performance. By systematically varying electrode materials and surface treatments, we will aim to determine how local interfacial phenomena influence global efficiency, thereby providing guidelines for the rational design of improved electrodes with reduced bubble-related losses.
Overall, this PhD project is highly innovative in its ability to access previously inaccessible interfacial phenomena at the nanoscale and to bridge the gap between interfacial soft matter, solid/liquid interfaces, fundamental surface science and applied electrochemical engineering. Its expected outcomes will contribute to both fundamental understanding and technological advances in hydrogen production, positioning it at the forefront of research on energy-related interfacial processes.
Keywords
Solid/liquid interfaces, nanobubbles, electrocatalysis, energy, hydrogen
Research Unit, UMR number and acronym
ESPCI – Soft Matter Science and Engineering, UMR 7615
Institute of Porous MAterials of Paris, UMR 8004
Description of the research Unit/subunit
The project team brings together complementary expertise from two researchers, J. Comtet and L. Assaud, based in two ESPCI research units : the Soft Matter Science and Engineering Laboratory (SIMM) and the Institute of Porous Materials of Paris (IMAP). J. Comtet’s research focuses on probing the transport and dynamics of soft matter at interfaces, at the nano- and molecular scale, using innovative experimental approaches ranging from scanning probe to single-molecule imaging. L. Assaud’s work centers on the characterization and optimization of novel two-dimensional electrochemical interfaces and electrocatalytic processes through nanostructuration.
This project is thus unique in bringing together complementary expertise in electrochemistry (IMAP), wetting and solid/liquid interfaces (SIMM), and quantitative scanning probe microscopy (IMAP, SIMM). By combining in situ electrochemical AFM with systematic surface engineering to directly observe the nucleation and early growth of gas bubbles at the nanoscale, this approach will enable the exploration of interfacial material properties at the nanometric scales, and open new avenues for the design of highly efficient electrodes for water electrolysis.
Name of the supervisor
Jean COMTET (jean.comtet@espci.fr)
Name of the co-supervisor
Loïc ASSAUD (loic.assaud@espci.fr)
3i Aspects of the proposal
The supervisors have a solid experience in PhD mentoring. Both PIs are young and dynamic, ensuring excellent supervision condition. The PhD candidate will be fully integrated into the laboratory’s research activities of both SIMM and IMAP through regular group seminars, team meetings, and scientific exchanges, providing a stimulating research environment. Specific scientific project supervision will include regular (weekly or biweekly) formal meetings where project progress will be reviewed in presence of the two PIs. The PhD supervisors will also be available for day-to-day hands on and practical questions, and the candidate will further benefit from supervision and interactions with Bruno Bresson, AFM expert and research engineer in the SIMM laboratory.
Intersectoriality
The project has a strong intersectoral potential through its direct relevance to industrial challenges in hydrogen production and surface engineering. A collaboration or secondment with an industrial partner such as TotalEnergies or Saint-Gobain will be sought to investigate the role of engineered surface coatings and functional interfaces on gas bubble nucleation, growth and detachment during water electrolysis. Initial contacts have already been established with both companies, providing a solid basis for future interactions, although no formal partnership has yet been implemented. Such a collaboration would facilitate the transfer of fundamental nanoscale insights toward the optimization of industrial electrode materials, while exposing the PhD candidate to innovation-driven research and technology development in a non-academic environment.
International
The project has a strong international dimension through established and planned collaborations with leading experts in interfacial science and advanced AFM. In particular, collaborations with Georg E. Fantner (EPFL, Switzerland), Kislon Voïtchovsky (Durham University, UK), and Susan Perkin (University of Oxford, UK) will provide complementary expertise in confined electrolyte studies under surface-forces, molecular-scale characterization of solid–liquid interfaces, and interfacial liquid structuring. The compulsory international secondment (minimum one month) will ideally take place at one of these partner laboratories, enabling knowledge transfer, access to complementary instrumentation, and strengthening the international impact and visibility of the project.
Interdisciplinarity
The project is highly interdisciplinary, bridging together concepts in interfacial physics, soft matter, electrochemistry, surface science and electrocatalysis. It combines advanced scanning probe microscopy, molecular-scale characterization of solid–liquid interfaces, electrochemical measurements and materials engineering to investigate gas bubble nucleation during water electrolysis. By linking nanoscale interfacial phenomena to macroscopic electrochemical performance, the project integrates fundamental physics and physical chemistry with challenges in energy conversion and materials design. This cross-disciplinary approach will provide the PhD candidate with broad expertise spanning experimental nanoscience, electrochemistry, surface engineering and data analysis, while fostering interactions between complementary scientific communities./p>
Expected profile of the candidate
We are looking for a master’s student with a background in physics, materials science, electrochemistry, or physical chemistry, who is excited to dive into an interdisciplinary project at the crossroads of soft matter, interfacial physics and physico-chemistry, liquid-state physics, electrochemistry, and electrocatalysis. The envisioned AFM experiments are technically demanding and require great care and precision : a strong aptitude for hands-on experimental work with complex, custom-built instruments — here, Atomic Force Microscopy — together with solid data analysis skills, will be key to making the most of this project. Beyond technical background, we are above all looking for someone curious, open-minded, and able to think independently, who is eager to take ownership of a research question at the frontier of physics and electrochemistry.
Important dates
Call for applications : from September 1st to October 31st 2026
Eligibility check results : November
3i Committee evaluation results : December
Interviews from the shortlisted candidates with the Selection Committee : January 2027
Start of the PhD : March 1st 2027