In Short:
New research reveals that bubbles forming on industrial electrodes only block a smaller area than previously thought. This discovery could lead to better electrode designs that improve efficiency and reduce material waste in processes like hydrogen production and carbon capture. An open-source software tool has been created to help scientists study bubble behavior, potentially leading to more effective and environmentally friendly solutions.
Impact of Bubble Formation on Electrochemical Processes
Industrial electrochemical processes, which employ electrodes to generate fuels and chemical products, face challenges due to the formation of bubbles. These bubbles can obstruct portions of the electrode surface, significantly diminishing the area available for active reactions and leading to a performance drop ranging from 10 to 25 percent.
New Insights into Bubble Interference
Recent research has unveiled a long-standing misconception about the degree of interference caused by these bubbles. The findings clarify how the blocking effect operates and could pave the way for innovative designs of electrode surfaces aimed at reducing inefficiencies in prevalent electrochemical processes.
Traditionally, it was assumed that the entire area of an electrode obscured by a bubble would be rendered inactive. However, the new research indicates that only a significantly smaller area, precisely the region where the bubble contacts the surface, is inhibited from engaging in electrochemical activity. These insights may inform novel patterns for surface engineering to minimize contact area and enhance overall efficiency.
The study’s findings are detailed in a paper published in the journal Nanoscale, authored by recent MIT graduate Jack Lake PhD ’23, graduate student Simon Rufer, and Kripa Varanasi, a professor of mechanical engineering, along with Ben Blaiszik and six other collaborators from the University of Chicago and Argonne National Laboratory. The research team has also released an open-source, AI-based software tool to assist engineers and scientists in automatically recognizing and quantifying bubble formation on various surfaces, marking a substantial advancement toward controlling the properties of electrode materials.
Widespread Applications of Gas-Evolving Electrodes
Gas-evolving electrodes, frequently featuring catalytic surfaces that facilitate chemical reactions, are integral in multiple sectors, including the production of ‘green’ hydrogen without fossil fuels, processes aimed at carbon capture that help mitigate greenhouse gas emissions, aluminum production, and the chlor-alkali process for manufacturing widely utilized chemical products.
These processes have extensive implications, as the chlor-alkali method alone accounts for 2 percent of all U.S. electricity consumption, while aluminum production constitutes 3 percent of global electricity usage. Furthermore, both carbon capture and hydrogen production are anticipated to expand significantly in the coming years as global efforts intensify toward achieving greenhouse gas reduction targets. Thus, the recent discoveries hold the potential for substantial impact, as articulated by Varanasi.
Engineering Bubble Interference for Enhanced Efficiency
Varanasi states, “Our work demonstrates that engineering the contact and growth of bubbles on electrodes can have dramatic effects” on how bubbles form and detach from the surface. “The realization that the area beneath bubbles can indeed be active establishes a new set of design principles for developing high-efficiency electrodes to mitigate the adverse impacts of bubbles.”
Rufer adds, “The broader literature compiled over the last couple of decades has suggested that not only the small area of contact but the entire area beneath the bubble is passivated.” The new research elucidates a crucial distinction between the existing models, influencing how electrodes should be developed to minimize performance losses.
Methodologies and Software Development
To validate their findings, the research team fabricated various electrode surfaces with different patterns of dots to nucleate and trap bubbles at varying sizes and distances. This approach enabled them to demonstrate that surfaces with widely spaced dots fostered larger bubble sizes while contributing only minimal areas of surface contact—effectively highlighting the divergence between expected and actual outcomes associated with bubble coverage.
The development of the software for bubble detection and quantification was fundamental to the team’s analysis. Rufer explains, “Our goal was to gather extensive data covering various electrodes, reactions, and bubble forms, which all exhibit subtle variations.” Creating a program capable of accurately identifying and tracking bubbles across diverse materials and lighting conditions was challenging, with machine learning playing a crucial role in this endeavor.
Future Implications and Environmental Benefits
This software facilitated the collection of substantial data regarding bubble formation, such as their location, size, and growth rate. The tool is now accessible for public use through a GitHub repository, allowing widespread application in this field.
Using the tool to correlate visual data on bubble dynamics with electrical performance metrics of the electrodes, the researchers successfully disproved prevailing theories, demonstrating that only the area of direct bubble contact is impacted. Video evidence further substantiated this finding, showcasing new bubbles actively evolving beneath larger bubbles.
The research team developed a comprehensive methodology that can be applied to assess the effects of bubbles on any electrode or catalyst surface. They quantified the bubble blocking effects using a new performance metric termed BECSA (Bubble-induced electrochemically active surface), as opposed to the conventional ECSA (electrochemically active surface area) typically utilized within the field. “The BECSA metric was a concept we defined in a previous study but lacked an effective estimation method until now,” explains Varanasi.
Overall, the realization that the area beneath bubbles can remain significantly active introduces a fresh set of design principles for high-performance electrodes. Thus, electrode designers are encouraged to focus on minimizing bubble contact area rather than just bubble coverage, achievable by manipulating electrode morphology and chemistry. Surfaces designed to manage bubble formation can enhance overall process efficiency, thereby reducing energy consumption and upfront material costs. Many of these gas-evolving electrodes rely on costly catalysts, such as platinum or iridium, and the outcomes of this research can guide the engineering of electrodes that mitigate material loss due to bubble-induced reactions.
Varanasi concludes, “The insights gained from this research could inspire new electrode designs that not only reduce the consumption of precious materials but also enhance the overall performance of electrolyzers,” which ultimately translates to significant environmental benefits on a large scale.
The research team comprised Jim James, Nathan Pruyne, Aristana Scourtas, Marcus Schwarting, Aadit Ambalkar, Ian Foster, and Ben Blaiszik at the University of Chicago and Argonne National Laboratory. The study received support from the U.S. Department of Energy under the ARPA-E program.
