In a groundbreaking development in the field of electrocatalysis, scientists have uncovered new insights into how catalysts behave during nitrate reduction, an important process for recycling nitrates into ammonia. This advancement, published in the journal Nature Materials, challenges long-standing assumptions about catalyst behavior and opens up new possibilities for designing more efficient catalysts. The research, titled “Revealing Catalyst Restructuring and Composition During Nitrate Electroreduction through Correlated Operando Microscopy and Spectroscopy,” highlights the dynamic nature of catalysts during the electrochemical process and could have significant implications for energy and environmental sustainability.
Understanding Electrocatalysts and Their Role in Industry
Catalysts are substances that accelerate chemical reactions without being consumed in the process. They play a pivotal role in numerous industrial applications, including energy production, fuel generation, and pharmaceutical manufacturing. In recent years, electrocatalysis has gained increasing attention due to its potential in sustainable energy technologies, such as hydrogen production and carbon dioxide reduction.
However, a key challenge in catalysis research is understanding how catalysts behave in real-time under working conditions. When an electric potential is applied to a catalyst, it can undergo structural and compositional changes that directly impact its effectiveness. This process is often likened to a chameleon that changes its color to match its environment. Traditionally, scientists assumed that once an electric potential was applied, catalysts would quickly transform into their most active form, similar to how a chameleon shifts to its most suitable color for survival.
But as new research from the Fritz Haber Institute of the Max Planck Society, in collaboration with scientists from the Helmholtz-Zentrum Berlin, reveals, this assumption is not always valid. The study provides new evidence that catalysts do not always transform into their ideal state as quickly or as predictably as previously thought.
A Novel Approach to Studying Catalysts
The research team employed a multi-modal approach, combining several advanced techniques to study the real-time behavior of catalysts during the nitrate reduction process. One of the key methods used was electrochemical liquid cell transmission electron microscopy (EC-TEM), which allowed the researchers to observe the structural evolution of catalysts in situ, while they were actively participating in the nitrate reduction reaction.
This technique proved to be invaluable in examining Cu2O (copper(I) oxide) pre-catalysts, which are commonly used in electrocatalysis. By directly observing the reaction process, the team could track how these cubic Cu2O particles underwent transformation during nitrate reduction.
To complement the EC-TEM observations, the researchers used additional techniques, including X-ray microscopy, X-ray spectroscopy, and Raman spectroscopy. These methods enabled them to detect and analyze the chemical changes occurring in the catalysts, and to determine whether the expected transformation into the Cu metal phase took place. More importantly, the team investigated whether this transformation was uniform across all catalyst particles or if different phases were maintained.
Unexpected Catalyst Behavior: A Mixture of Phases
One of the most surprising findings of the study was that the Cu2O pre-catalysts did not rapidly transform into the expected metallic copper (Cu) phase. Instead, the catalysts remained in a mixed state, consisting of copper metal, copper oxide, and copper hydroxide, even after prolonged exposure to the reaction conditions. This mixture of phases was maintained for a longer time than previously expected, challenging the conventional wisdom that catalysts would quickly settle into their optimal active form.
The study revealed that the composition and structure of the catalyst depend on a variety of factors, including the electric potential applied, the chemical environment, and the reaction duration. In other words, catalysts can remain in a non-ideal, mixed phase for extended periods, which could have significant implications for designing more efficient and stable catalysts for industrial applications.
Implications for Ammonia Production
One of the key motivations behind this research is the potential to use nitrate reduction as a means of recycling waste nitrates and converting them back into ammonia. Ammonia is a critical component in fertilizers, which are essential for food production. Traditional methods of ammonia synthesis, such as the Haber-Bosch process, are energy-intensive and rely on high temperatures and pressures. These processes are also dependent on fossil fuels, which contribute to carbon emissions and climate change.
The new insights gained from this study could pave the way for more sustainable ammonia production methods. By using electrocatalysis driven by renewable electricity, researchers hope to create a more energy-efficient and environmentally friendly alternative to the Haber-Bosch process. The ability to control and optimize the behavior of catalysts during nitrate reduction could significantly improve the efficiency of ammonia production and help reduce carbon emissions.
Dr. See Wee Chee, group leader at the Interface Science Department of the Fritz Haber Institute and corresponding author of the study, emphasized the importance of the team’s findings. “It is unexpected that we get different phases during the reaction, especially when we start from a single form of a single-element pre-catalyst,” he said. “More importantly, this mixed state can be maintained for a long time, which is valuable insight if we want to design more efficient catalysts.”
Advancing Catalyst Design
The results of this study offer a new perspective on how catalysts behave during nitrate electroreduction and provide valuable information for future catalyst design. Understanding how different phases evolve during the reaction can help researchers develop catalysts that are more stable, efficient, and selective in the production of ammonia.
Prof. Beatriz Roldán, director of the Interface Science Department at the Fritz Haber Institute and co-corresponding author, also highlighted the broader implications of the research. “Industrially, ammonia is synthesized via the gas-phase Haber-Bosch thermal catalysis method, which takes place at moderate temperatures (450–550°C) but at high pressures (150 bar) with a large consumption of fossil-generated hydrogen (H2),” she said. “The challenge we tackled here was to find an alternative method for ammonia synthesis with reduced carbon emissions. This was accomplished by following a direct electrocatalytic route driven by renewable electricity.”
The Role of Advanced Real-Time Observation Techniques
The study also underscores the importance of advanced real-time observation techniques in catalysis research. By using methods like EC-TEM, X-ray microscopy, and Raman spectroscopy, the team was able to capture detailed information about the chemical and structural changes occurring in catalysts during the reaction. These techniques allow scientists to study catalysts in action and gain a deeper understanding of their complex behavior under different conditions.
This ability to monitor catalysts in real-time is crucial for developing more efficient and sustainable catalytic processes. It provides insights into the dynamic nature of catalysts and helps researchers design better catalysts for a wide range of applications, from renewable energy production to industrial chemical synthesis.
Conclusion
The research published in Nature Materials marks a significant step forward in the field of electrocatalysis, providing new insights into how catalysts behave during nitrate reduction. By challenging long-held assumptions about catalyst transformation, the study opens up new possibilities for designing more efficient and stable catalysts for ammonia production. As the world seeks more sustainable methods of producing ammonia and other essential chemicals, this research offers a promising path toward reducing carbon emissions and improving energy efficiency. The study also highlights the value of advanced real-time observation techniques, which allow scientists to study catalysts under working conditions and gain a deeper understanding of their complex behavior.
This research is an important contribution to the ongoing effort to develop more sustainable and efficient catalytic processes, paving the way for greener energy solutions and a more sustainable future.
Reference: Aram Yoon et al, Revealing catalyst restructuring and composition during nitrate electroreduction through correlated operando microscopy and spectroscopy, Nature Materials (2025). DOI: 10.1038/s41563-024-02084-8