Key Takeaways & Executive Findings
- •• • Achieved 92.6% NH3 conversion and 9.7 mmol g−1 min−1 H2 production rate at 425 °C (GHSV=9000 mL h−1 g_cat−1), a 125 °C reduction in operating temperature vs. conventional Co catalysts, enabling lower energy costs for on-demand hydrogen generation. • • The LA-L(A+B)-LB active site configuration, formed by Ce and N co-modification, lowers the Schottky barrier at the Co-support interface, facilitating hydrogen spillover and shifting the reaction to a Mars-van Krevelen mechanism, which bypasses the rate-limiting N2 desorption step. • • Isotopic labeling and in-situ DRIFTS confirm the interfacial mechanism, providing direct evidence for the promotional effect of O-vacancies and N-coordination on hydrogen spillover, which is critical for rational catalyst design. • • The catalyst demonstrates exceptional low-temperature activity, making it a promising candidate for industrial ammonia decomposition units that operate at reduced temperatures, thereby improving process efficiency and catalyst longevity.
Abstract
Ammonia decomposition is a key process for generating COx-free hydrogen, yet conventional cobalt catalysts require high temperatures (>550 °C) to overcome the strong Co–N binding that limits N2 desorption. Here we report a novel Co catalyst supported on a Ce and N co-modified perovskite (Co@La_xCe_{1-x}AlO_{3-y}N_z) that achieves 92.6% ammonia conversion with a hydrogen production rate of 9.7 mmol g−1 min−1 at 425 °C and GHSV = 9000 mL h−1 g_cat−1, representing a 125 °C reduction in operating temperature relative to conventional Co-based catalysts. Mechanistic studies using isotopic labeling and in-situ DRIFTS reveal that synergistic Ce and N modification creates a unique LA-L(A+B)-LB active site configuration, which lowers the Schottky barrier at the metal-support interface and promotes facile hydrogen spillover. The reaction proceeds via an interfacial Mars-van Krevelen mechanism, contrasting with the traditional Langmuir-Hinshelwood pathway on conventional Co catalysts. This work provides new insights for designing low-temperature Co-based ammonia decomposition catalysts.
1. Introduction
Ammonia decomposition is a promising route for generating COx-free hydrogen, but its industrial deployment is hindered by the high operating temperatures (>550 °C) required by most catalysts. Cobalt-based catalysts are attractive non-precious metal alternatives, yet their activity is limited by the strong Co–N binding energy, making N2 desorption the rate-determining step. Conventional supports like Al2O3 induce strong metal-support interactions (SMSI) that create a significant Schottky barrier, impeding hydrogen spillover and confining the reaction to individual Co sites via a Langmuir-Hinshelwood pathway.
To overcome this bottleneck, we engineered the catalyst-support interface by incorporating Ce and N into a LaAlO3 perovskite structure. This modification reduces the density of Lewis acid sites, enhances surface basicity, and introduces oxygen vacancies, creating a unique LA-L(A+B)-LB active site configuration. This structure lowers the Schottky barrier, promotes hydrogen spillover, and shifts the reaction to an interfacial Mars-van Krevelen mechanism, enabling high ammonia conversion at remarkably low temperatures. Our findings provide a new strategy for designing efficient low-temperature Co-based catalysts for ammonia decomposition.
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Cheng Zuo, Qian Su, Jing Wang, Hui Zhao, Min Wang, Xishi Tai, Xiangke Wang (2026). Enhanced hydrogen spillover effect in low-temperature ammonia decomposition via N-coordination and O-vacancy-activated Co/La_xCe_{1-x}AlO_{3-y}N_z catalyst. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-3831-0Research & Educational Purpose Only: The translations, structured abstracts, analytical annotations, and data reports provided by SinoGreenTechare intended exclusively for academic research, internal corporate R&D, and educational benchmarking. They do not constitute formal engineering, chemical safety, legal, or professional advice.
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Frequently Asked Questions
What is the specific role of Ce and N co-modification in enhancing the catalytic performance?
Ce and N co-modification creates a unique LA-L(A+B)-LB active site configuration that lowers the Schottky barrier at the Co-support interface. This facilitates hydrogen spillover from the support to Co sites, promoting the Mars-van Krevelen mechanism and reducing the activation barrier for N–H bond cleavage, as evidenced by isotopic labeling and in-situ DRIFTS.
How does the catalyst's performance compare to conventional Co-based catalysts under similar conditions?
The optimized Co@La_xCe_{1-x}AlO_{3-y}N_z catalyst achieves 92.6% NH3 conversion and a H2 production rate of 9.7 mmol g−1 min−1 at 425 °C, which is 125 °C lower than the operating temperature of conventional Co-based catalysts under similar GHSV (9000 mL h−1 g_cat−1).
What is the proposed reaction mechanism and how was it verified?
The reaction proceeds via an interfacial Mars-van Krevelen mechanism, where lattice oxygen participates in the oxidation steps, rather than the traditional Langmuir-Hinshelwood pathway. This was confirmed using isotopic labeling and in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), which identified the active site configuration and hydrogen spillover dynamics.
What are the potential scalability challenges for industrial application?
While the catalyst shows exceptional low-temperature activity, scalability challenges include the synthesis of the perovskite support with controlled Ce and N doping, maintaining O-vacancy concentration, and ensuring long-term stability under industrial conditions. Further studies are needed to assess catalyst durability and regeneration under high GHSV and thermal cycling.
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