Synergistic Electronic Modulation of Ru Sites via N-Doped CeO2 and Cs Promotion for High Efficiency H2 Generation from Ammonia Decomposition

Abstract

Growing attention to using ammonia (NH₃) as an energy carrier to produce CO_x-free H₂ at low temperatures and supply it on demand at sites has renewed research interest. This study utilizes N-doped CeO₂ material to support Ru via a solvothermal process for NH₃ decomposition. The synergistic integration of N-doped CeO₂ as a support and cesium (Cs) as a promoter has led to a breakthrough in catalytic activity. Advanced analysis techniques, including N₂ physisorption, ICP, HAADF-STEM, CO pulse chemisorption, XRD, XPS, XAS, Raman, EPR, and temperature-programmed analysis, are employed to elucidate the beneficial properties of catalysts for the NH₃ decomposition. Additionally, density functional theory (DFT) calculations provided atomic-scale insights, revealing that N-doping modulates the electronic properties of the Ru sites, thereby lowering the energy barrier for recombinative N₂* desorption and enhancing high NH₃ decomposition activity at low temperatures. Ru/2N-CeO₂ and Cs-Ru/2N-CeO₂ exhibited superior catalytic efficiency with a H₂ yield of approximately 1,407 mmol/min/g_Ru and 2,115 mmol/min/g_Ru , respectively, and excellent stability during 100 h at 450 ^oC with WHSV = 30,000 mL NH₃/g_cat./h. This study demonstrates that the syngenetic effects of increased oxygen vacancies (Ov) and the effective modulation of the electronic environment of Ru sites, which are optimal for enhancing recombinative N₂ desorption, are vital for developing Ru-based catalysts for NH₃ decomposition.