Microwave-assisted deep eutectic solvent synthesis of Sr-doped LaNiO3-derived Ni-based oxides for efficient NH3 decomposition

Abstract

Efficient ammonia (NH₃) decomposition is crucial for on-demand hydrogen generation. Although Ru-based catalysts show excellent performance, their high cost necessitates the development of non-noble alternatives, among which supported Ni catalysts have drawn significant attention. However, their NH₃ decomposition activity remains unsatisfactory, and Ni particles tend to agglomerate under the high temperatures required for NH₃ decomposition, leading to performance degradation. Herein, we report a microwave-assisted deep eutectic solvent (DES) method to synthesize Sr-doped LaNiO₃ (La_xSr_1−xNiO₃) perovskites as precursors for highly dispersed, thermally stable Ni catalysts. After reduction, the resulting La_xSr_1−xNiO₃-R catalysts exsolve socketed Ni nanoparticles embedded within La₂O₃, establishing strong metal–support interactions that effectively suppress sintering. Sr incorporation substantially enhances the alkalinity of La₂O₃, thereby facilitating the rate-limiting N–N recombination step. Benefiting from these synergistic effects, the optimal La_0.7Sr_0.3NiO₃-R catalyst exhibits outstanding activity and stability, achieving NH₃ conversions of 98.7% and 82.8% at WHSVs of 30 000 and 60 000 mL g_cat⁻¹ h⁻¹ at 550 °C, corresponding to H₂ generation rates of 33.0 and 55.4 mmol g_cat⁻¹ min⁻¹, respectively—among the highest reported for non-noble metal catalysts. Moreover, the catalyst maintains nearly 100% NH₃ conversion over 200 h. This work provides an effective strategy for designing robust, high-performance Ni-based catalysts for sustainable hydrogen production from ammonia.