Yttrium-doped nickel catalyst boosts ammonia to hydrogen conversion efficiency

Mar 12, 2026

Researchers developed an yttrium doped nickel catalyst that creates stable oxygen vacancies to improve ammonia decomposition for clean hydrogen production.

(Nanowerk News) Researchers at Tohoku University have developed a low cost nickel based catalyst enhanced with yttrium that significantly improves the efficiency of converting ammonia into hydrogen, offering a carbon free route to clean fuel production (Journal of Catalysis, “Y-induced oxygen vacancy engineering and local electronic reconstruction for enhanced ammonia decomposition over Ni1Ce1-xYxOα“). The yttrium doped catalyst, designated Ni1Ce1-xYxOα, addresses the persistent challenge of making non-noble metal catalysts active enough for practical ammonia decomposition, a reaction that produces hydrogen without generating harmful emissions.

Key Findings

Ammonia carries a high density of hydrogen by weight, and splitting it into hydrogen and nitrogen is an attractive alternative to fossil fuel based hydrogen production because the process generates no carbon dioxide. The main obstacle, however, is that the reaction requires a catalyst to proceed at practical temperatures and rates. Noble metals such as ruthenium are highly effective for this purpose but are expensive and scarce, which limits their large scale deployment. The structure and elements distribution. (Image: Tohoku University) Nickel is a promising substitute because of its low cost and wide availability. Yet nickel catalysts typically lack the intrinsic activity needed and face high energy barriers during the final step of the reaction, where nitrogen atoms must combine and detach from the catalyst surface. The Tohoku University team tackled both problems simultaneously by using yttrium as a dual-function promoter within a nickel-ceria oxide structure. The yttrium doping serves two purposes. First, it generates a large number of stable oxygen vacancies on the catalyst surface. These vacancies are sites where oxygen atoms are missing from the crystal lattice, and they play a critical role in facilitating the chemical steps of ammonia breakdown. Second, the incorporation of yttrium reshapes the local electronic structure around the nickel atoms that serve as active sites, where ammonia molecules bind and undergo sequential removal of their hydrogen atoms. The team evaluated a series of catalyst compositions with varying yttrium to cerium ratios and found that the formulation with equal parts yttrium and cerium, Ni1Ce0.5Y0.5Oα, delivered the best performance. Testing was conducted at a gas hourly space velocity of 30,000 mL per gram of catalyst per hour, with a reduction temperature of 400 degrees Celsius. The hydrogen formation rate of this optimized composition at 500 degrees Celsius exceeded that of comparable non-noble metal catalysts documented in existing databases. The researchers also measured the apparent activation energy for each composition and examined how the hydrogen production rate responded to changes in ammonia and hydrogen partial pressures. These kinetic analyses confirmed that the yttrium doped variant lowered the energy needed to initiate N-H bond breaking and facilitated the coupling of adsorbed nitrogen atoms, two steps widely regarded as bottlenecks in ammonia decomposition over nickel catalysts. Structural characterization using transmission electron microscopy, high resolution TEM, and scanning TEM with elemental mapping showed that the catalyst maintained its structural integrity after catalysis. The nickel, cerium, and yttrium components remained well distributed, and the oxygen vacancy rich surface persisted through the reaction, indicating strong long term stability. “This study provides a practical pathway toward more sustainable, affordable hydrogen energy systems,” says Associate Professor Yizhou Zhang. “The findings support the broader transition to clean energy, contributing to reduced carbon emissions and the future deployment of hydrogen-based vehicles and power generation.” The work demonstrates that strategic incorporation of a relatively inexpensive rare earth element can transform an otherwise modest nickel catalyst into one that rivals far more costly noble metal systems. By establishing a clear relationship between yttrium content, oxygen vacancy density, electronic structure, and catalytic performance, the study offers a design framework that could be extended to other non-noble metal catalysts for ammonia decomposition.