Nanocatalysts, with their small size and high surface area-to-volume ratio, significantly enhance catalytic activity in industrial processes such as ammonia production.1 By integrating nanocatalysts, ammonia synthesis benefits from heightened efficiency and sustainability, allowing for lower temperatures and pressures, ultimately reducing energy consumption and operational costs.1
Image Credit: Vladimir Nenezic/Shutterstock.com
The global demand for ammonia continues to surge, driven by its pivotal role in various industries such as agriculture, pharmaceuticals, and chemicals. As the world continues to invest in sustainable and environmentally friendly technologies, the spotlight has turned towards catalysis as a key player in enhancing ammonia production processes.2
Here, we explore how nanocatalysts can revolutionize ammonia production by addressing the energy-intensive and environmentally challenging aspects of the century-old, Haber-Bosch process, offering a promising pathway toward sustainable ammonia synthesis.
Importance of Ammonia Production in Various Industries
Ammonia proves to be a versatile compound, acting as a foundational element across multiple industries. Within agriculture, it plays a crucial role in fertilizers, fostering plant growth and bolstering crop yields. Additionally, the chemical and pharmaceutical sectors leverage ammonia for synthesizing diverse products like plastics, pharmaceuticals, and cleaning agents. Given its broad range of applications, the optimization of ammonia production processes becomes essential to meet global demand in a sustainable manner.2
Nanocatalysts play a pivotal role in optimizing ammonia production, a critical process for global fertilizer and industrial manufacturing. Traditionally relying on Haber-Bosch catalysis with iron-based catalysts under high temperatures and pressures, the integration of nanocatalysts offers numerous advantages, fostering heightened efficiency and sustainability in ammonia synthesis.3
Advantages of Nanocatalysts in Ammonia Synthesis
Nanocatalysts present several benefits in the synthesis of ammonia. These catalysts promote heightened reactivity and selectivity, leading to increased efficiency and lower energy consumption. Furthermore, the environmentally friendly synthesis of some nanocatalysts aligns with the growing demand for sustainable practices, making nanocatalysts an attractive option for advancing ammonia production with reduced environmental impact.1 The capacity of nanocatalysts to expedite chemical reactions enhances both yield and selectivity in ammonia production, representing a noteworthy advancement in the field.2
The use of nanostructured catalysts, such as nanoparticles or nanocomposites, ensures controlled environments, enhancing performance and stability over extended periods. Nanocatalysts often permit regeneration, extending their lifespan and contributing to sustainable and cost-effective ammonia production. Ongoing research into innovative nanomaterials further promises improvements in efficiency, underscoring the potential of nanocatalysts to revolutionize ammonia synthesis in diverse industrial applications.2
Examples of Nanocatalysts in Improving Ammonia Production Efficiency
Various categories of nanocatalysts such as metal nanoparticles, graphene-based nanocatalysts, metal oxide nanocatalysts, carbon-based nanotubes, bimetallic nanocatalysts, doped nanocatalysts, and metal-organic frameworks (MOFs) exhibit impressive potential for enhancing both efficiency and yield in the synthesis of ammonia. Metal nanoparticles, including ruthenium and iron, display outstanding catalytic activity during ammonia production. These nanocatalysts provide a finer degree of control over reaction kinetics, leading to enhanced conversion rates and a decrease in the formation of by-products.4
Electrosynthesis of Ammonia Using Porous Bimetallic Pd–Ag Nanocatalysts in Liquid- and Gas-Phase Systems
Researchers led by M. A. El-Sayed’s group (2020) from Georgia Institute of Technology, USA explores the use of porous bimetallic Pd-Ag nanocatalysts in both gas-phase and liquid-phase electrochemical cells, demonstrating effective ammonia production at current densities exceeding 1 mA cm-2 under ambient conditions.
Their research underscores the significance of optimizing both catalyst modification and cell configuration for achieving high-performance N2 electrolysis in ammonia production. This findings were published in ACS Catalysis.5
Atomic Coordination Environment Engineering of Bimetallic Alloy Nanostructures for Efficient Ammonia Electrosynthesis from Nitrate
Wang et al. (2023) synthesized ultrathin nanosheet-assembled RuFe nanoflowers with low-coordinated Ru sites, significantly enhancing nitrate reduction reaction (NO3RR) performance in neutral electrolytes. The study focuses on improving the electrochemical NO3RR to produce ammonia, a key element in balancing the global nitrogen cycle.
Their findings, published in Proceedings of the National Academy of Sciences, suggest the potential application of RuFe nanoflowers in next-generation electrochemical energy systems, as demonstrated in rechargeable zinc-nitrate batteries.6
One-Pot Synthesis of Ruthenium-Based Nanocatalyst Using Reduced Graphene Oxide as Matrix for Electrochemical Synthesis of Ammonia
Researchers from University of North Dakota, United States presented a one-step synthetic approach for Ru-based nanocatalysts, employing reduced graphene oxide (rGO) as a promoter. This technique aimed to enhance electrical conductivity and facilitate hydrogen trapping, thereby enabling electrochemical ammonia synthesis under ambient conditions.
The outcomes of their study advocate for continued efforts in refining the catalyst, ideally customizing it for compatibility with a solid-state electrolyte at elevated temperatures to achieve commercially relevant rates of NH3 production. They published this article in ACS Appl. Mater. Interfaces.7
Future Trends in Nanocatalyst-Assisted Ammonia Production
The future of nanocatalyst-assisted ammonia production holds significant promise, as ongoing research aims to enhance catalytic efficiency and understand the underlying mechanisms.
Advanced materials, like graphene-based nanocatalysts, show potential for improved reactivity and selectivity. The development of precise nanoengineering techniques, allowing control over particle size and morphology, is expected to optimize nanocatalyst design, enhancing their activity and stability during ammonia synthesis.1
Additionally, future trends may involve designing multifunctional nanocatalysts capable of promoting multiple steps in the ammonia synthesis process simultaneously, potentially improving overall efficiency. Furthermore, aligning nanocatalyst-assisted ammonia production with renewable energy sources, such as solar or wind power, is a potential trend for a more sustainable and energy-efficient process.1
Challenges
A significant challenge in advancing nanocatalyst-assisted ammonia production lies in the transition from laboratory to industrial scale. Maintaining catalytic efficiency and stability at a larger scale presents technical and engineering hurdles, and the associated costs of synthesizing and implementing nanocatalysts pose obstacles for widespread adoption.1
Persistent challenges include improving the stability and durability of nanocatalysts under harsh operating conditions, addressing concerns about nanoparticle toxicity, and ensuring the safe handling and disposal of nanomaterials used in catalysts. It is expected to focus on resolving these safety issues to promote the responsible use of nanocatalysts in industrial applications.1
In conclusion, nanocatalysts are emerging as a transformative force in the realm of ammonia production. As industries pursue sustainable and efficient practices, the adoption of nanocatalysts provides a viable route to meet these objectives. The benefits, encompassing heightened efficiency, diminished energy usage, and enhanced selectivity, establish nanocatalysts as pivotal contributors to the progression of ammonia synthesis techniques. Despite existing challenges, continual research and technological progress are anticipated to elevate the role of nanocatalyst-assisted ammonia production, positioning it as a more prominent and sustainable approach in the future.
What Makes Nanocatalysts Ideal for Industrial Chemistry?
References and Further Reading
- Qureshi, S., et al. (2022) A Review on Sensing and Catalytic Activity of Nano-Catalyst for Synthesis of One-Step Ammonia and Urea: Challenges and Perspectives. Chemosphere, 291, p. 132806. doi.org/10.1016/j.chemosphere.2021.132806.
- Saadatjou, N., et al. (2015) Ruthenium Nanocatalysts for Ammonia Synthesis: A Review. Chem. Eng. Commun. 202 (4), pp. 420–448. doi.org/10.1080/00986445.2014.923995.
- Bell. 2018_Pnas_Si_Spe. Proc. Natl. Acad. Sci. 2017, 120, 2017. https://doi.org/10.1073/pnas.
- Li, L., et al. (2022) Size Sensitivity of Supported Ru Catalysts for Ammonia Synthesis: From Nanoparticles to Subnanometric Clusters and Atomic Clusters, Chem 8 (3), pp. 749–768. doi.org/10.1016/j.chempr.2021.11.008.
- Nazemi, M., et al. (2020) Electrosynthesis of Ammonia Using Porous Bimetallic Pd–Ag Nanocatalysts in Liquid- and Gas-Phase Systems. ACS Catalysis, 10 (17), pp. 10197–10206. doi.org/10.1021/acscatal.0c02680.
- Wang, Y., et al. (2023) Atomic Coordination Environment Engineering of Bimetallic Alloy Nanostructures for Efficient Ammonia Electrosynthesis from Nitrate. Proceedings of the National Academy of Sciences of the United States of America, 120 (32), p. e2306461120. doi.org/10.1073/pnas.2306461120.
- Sun, W., et al. (2022) One-Pot Synthesis of Ruthenium-Based Nanocatalyst Using Reduced Graphene Oxide as Matrix for Electrochemical Synthesis of Ammonia. ACS Applied Materials & Interfaces. doi.org/10.1021/acsami.2c18413
