NH3 Decomposition for H2 Generation: Effects of Cheap Metals and Supports on Plasma鈥揅atalyst Synergy

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• 作者：Li Wang ; Yanhui Yi ; Yue Zhao ; Rui Zhang ; Jialiang Zhang ; Hongchen Guo
• 刊名：ACS Catalysis
• 出版年：2015
• 出版时间：July 2, 2015
• 年：2015
• 卷：5
• 期：7
• 页码：4167-4174
• 全文大小：500K
• ISSN：2155-5435

文摘

NH₃ decomposition is important because of its potential use in generating CO-free H₂. In this study, several cheap metals (Fe, Co, Ni, and Cu) and a series of supports (zeolite materials: TS-1 um, TS-1 nm, HZSM-5 nm, and NaZSM-5 nm; SiO₂-based materials: fumed SiO₂ and SiO₂-ball; and metal oxide materials: r鈥?Al₂O₃ and TiO₂) were used to prepare supported catalysts. X-ray fluorescence, N₂ physisorption, X-ray diffraction, transmission electron microscopy, Fourier-transform infrared spectroscopy, temperature-programmed desorption, mass spectrometry, temperature-programmed reduction, and electrical property analysis were used to investigate the effect of the catalyst on the synergy between a plasma (produced by dielectric barrier discharge) and the catalyst in NH₃ decomposition. The results show that the synergy depends strongly on the strength of the metal鈥搉itrogen (M鈥揘) bond, and the relative dielectric constant (蔚_d) of the support. When Fe, Co, Ni, and Cu were supported on fumed SiO₂, the order of the strengths of the M鈥揘 bonds was Cu鈥揘 < Ni鈥揘 < Co鈥揘 < Fe鈥揘. Among the catalysts, Co/fumed SiO₂ showed a stronger synergy with the plasma and gave higher NH₃ conversion in plasma catalysis. Co catalysts supported on fumed SiO₂, SiO₂-ball, and r鈥?Al₂O₃, which have small 蔚_d values, had stronger synergies with plasma and therefore gave higher NH₃ conversions. The relative dielectric constant of the support correlated well with NH₃ conversion in plasma catalysis. These results show that the relative dielectric constant is an essential parameter in developing catalyst supports for plasma conditions. This study provides direct proof that the recombinative desorption of adsorbed N atoms is the rate-limiting step in the catalytic decomposition of NH₃ over cheap metal catalysts such as Fe, Co, and Ni and that there is synergy between plasma and cheap metal catalysts in plasma-catalytic NH₃ decomposition.