Green hydrogen is the theoretical gold standard for sustainable fuel. It’s earmarked as the ideal pathway for decarbonising hard-to-abate sectors like cement, chemical, and steel refining. Yet the technology remains in its infancy, with significant barriers to large-scale implementation. Currently, a mere 1% of hydrogen production qualifies as “green”. Grey hydrogen produced using fossil fuel-driven processes still predominates. Realising truly green hydrogen production at meaningful scales requires enormous investment in renewable infrastructures and efficient hydrogen production processes.
Two primary methods exist for generating green hydrogen: the electrolysis of water and ammonia splitting (or cracking). Electrolysis involves using electricity, preferably from renewable sources, to split water (H₂O) into hydrogen (H₂) and oxygen (O₂) via an electrolyzer. It produces pure hydrogen directly from water without emitting carbon. In contrast, ammonia splitting decomposes ammonia (NH₃) into hydrogen and nitrogen (N₂) through high-temperature catalytic cracking. This method relies on pre-produced ammonia, which is easier to store and transport than hydrogen. While electrolysis is clean if powered by renewables, ammonia splitting requires energy input for heating, impacting overall efficiency.
Another fundamental difference between these two methods is the type of catalysts employed. This article explores the differences between catalysts utilized in electrolysis and ammonia splitting, highlighting the trends and advancements in this field.
Electrolysis Catalysts
One method of creating green hydrogen is through electrolysis. Utilizing an electrolyzer, which contains two electrodes (an anode and a cathode), electrolysis can split water into hydrogen and oxygen. Catalysts can enhance the efficiency of the reactions that occur within the electrodes.
Anode Catalysts
At the anode, the oxygen evolution reaction (OER) occurs, which involves the oxidation of water to release oxygen gas. This reaction is sluggish and requires highly efficient catalysts. These catalysts include materials like:
- Precious Metals: These metals, particularly platinum and iridium, are commonly used due to their superior catalytic properties and stability under oxidative conditions. However, these metals are expensive and scarce.
- Transition Metal Oxides: Manganese oxides, cobalt oxides, and nickel oxides have emerged as promising candidates because of their good catalytic activity and lower costs.
Cathode Catalysts
The hydrogen evolution reaction (HER) occurs at the cathode, where water molecules gain electrons to form hydrogen gas. These catalysts use materials like:
- Platinum: Platinum is a preferred catalyst for HER thanks to its exceptional efficiency and durability. However, the high cost of platinum necessitates the development of cheaper alternatives.
- Nickel-Based Catalysts: They show promise as cost-effective HER catalysts because of their balance between performance and affordability. This makes them attractive for large-scale hydrogen production.
Ammonia Splitting Catalysts
Ammonia splitting, or ammonia decomposition, is an alternative method to produce hydrogen. This process involves breaking the nitrogen-hydrogen (N-H) bonds in ammonia (NH₃) to yield hydrogen and nitrogen gases. The catalytic activation of N-H bonds is essential for efficient ammonia decomposition, requiring robust and selective catalysts. Ammonia splitting catalysts can be made out of many materials:
- Ruthenium: Ruthenium is one of the most active catalysts for ammonia splitting. It is often supported on oxides like zirconia and alumina to enhance its stability and dispersion. While ruthenium exhibits excellent catalytic activity, its high cost limits its widespread use.
- Iron and Nickel: They act as more economical alternatives for ammonia splitting. Iron nanoparticles supported on carbon and nickel catalysts supported on rare earth oxides or aluminates have shown promising results in activating N-H bonds.
- Cobalt-Molybdenum and Mixed Metal Oxides: These materials are being investigated for ammonia decomposition. They leverage the synergistic effects of multiple metals to enhance catalytic activity and stability.
Comparing Green Hydrogen Catalysts
The choice of catalysts for green hydrogen production is influenced by the nature of chemical reactions related to electrolysis and ammonia splitting. Electrolysis relies heavily on precious metal catalysts like platinum and iridium for their high efficiency in OER and HER. In contrast, ammonia splitting benefits from transition metal catalysts such as iron, nickel, and cobalt-molybdenum because of their ability to effectively activate N-H bonds.
Enhancing the Efficiency of Ammonia Splitting Catalysts for Generating Green Hydrogen with Nikalyte Technology
At Nikalyte, we want to utilize our cutting-edge nanoparticle technology to advance your ammonia splitting catalysts and improve their creation of green hydrogen. Our expertise in nanoparticle deposition ensures your nickel catalysts are efficient and tailored to meet specific functional requirements. Our flagship tool, the Nikalyte NL-UHV, enables precise control over nanoparticle composition, formation, and size.
Collaborate with our team of specialists to discover how Nikalyte’s advanced technologies can elevate your ammonia splitting processes. That way you can produce green hydrogen. We offer bespoke solutions to ensure your nickel catalysts deliver maximum efficiency and reliability in green hydrogen production. Contact Nikalyte now to learn more about our innovative nanoparticle deposition tools and how they can enhance your ammonia splitting catalysts for green hydrogen production.