Reaction mechanism and kinetics for hydrolytic dehydrogenation of ammonia borane on a Pt/CNT catalyst

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• 作者：Wenyao Chen ; Dali Li ; Zijun Wang ; Gang Qian ; Zhijun Sui ; Xuezhi Duan ; Xinggui Zhou ; Isaac Yeboah and De Chen
• 刊名：AIChE Journal
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：63
• 期：1
• 页码：60-65
• 全文大小：428K
• ISSN：1547-5905

文摘

A reaction mechanism is proposed for hydrolytic dehydrogenation of ammonia borane on a Pt/CNT catalyst. A combination of thermodynamic analysis and FTIR measurement reveals that B-containing byproducts are mainly in the form of an NH₄B(OH)₄-B(OH)₃ mixture rather than NH₄BO₂ reported previously. The revised main reaction is NH3BH3+4H2O→NH4++B(OH)4−+3H2↑, involving the B–H, B–N, and O–H bond cleavages. Isotopic experiments using D₂O instead of H₂O as reactant or introducing D₂ into the reaction atmosphere suggest the O–H bond cleavage being in the rate-determining step, and an unfavorable occurrence of the chemisorbed H₂O dissociation (i.e., the direct O–H bond cleavage), respectively. Different reaction pathways with indirect O–H bond cleavages are analyzed, and then NH3BH2*+H2O*→NH3BH2(OH)*+H* is suggested as the rate-determining step. Subsequently, a Langmuir–Hinshelwood kinetic model is developed, which fits well with the experimental data.