In Situ Synthesis of Ni(0) Catalysts Derived from Nickel Halides for Hydrolytic Dehydrogenation of Ammonia Borane
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In Situ Synthesis of Ni(0) Catalysts Derived from Nickel Halides for Hydrolytic Dehydrogenation of Ammonia Borane Lan Yang • Wei Luo • Gong-Zhen Cheng
Received: 14 April 2013 / Accepted: 2 June 2013 Ó Springer Science+Business Media New York 2013
Abstract Amorphous nickel catalysts derived from nickel halides (NiF2, NiCl2, NiBr2, NiI2) were in situ synthesized in an aqueous solution of NaBH4/NH3BH3. The halide anions have effects on the formation of Ni(0) catalysts, which can further affect the catalytic activities and activation energies of the catalysts for the hydrolysis of ammonia borane. The PVP stabilized catalysts have higher hydrogen evolution rates and durabilities than bare Ni catalysts for the hydrolysis of ammonia borane. The catalysts derived from NiBr2 stabilized by PVP present the highest catalytic activity and the lowest activation energy, which has been measured to be 25.58 kJ/mol. This value is lower than most of reported Nibased catalysts and even noble-metal containing catalysts. The results of mercury poisoning experiment reveal that Ni(0) catalysts derived from NiBr2 are heterogeneous catalysts in the hydrolysis of ammonia borane. Keywords Nickel catalysts Anion effect Hydrolysis Ammonia borane Heterogeneous catalyst
1 Introduction Hydrogen has the potential to replace petroleum as the primary fuel for transportation and remote power application [1–3]. It is strongly believed that hydrogen can help to address the growing demand for energy and slow down global climate change. The development of safe, efficient L. Yang W. Luo (&) G.-Z. Cheng (&) College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, Hubei, People’s Republic of China e-mail: [email protected] G.-Z. Cheng e-mail: [email protected]
and convenient hydrogen storage methods is a major hurdle that must be overcome before the widespread use of hydrogen becoming practical. Consequently, various hydrogen storage approaches are currently being investigated, including metal hydride [4], sorbent materials [5] and chemical hydride systems [6]. Boron–nitrogen containing compounds have attracted much attention recently for being used as hydrogen storage materials due to their high gravimetric densities and favorable kinetics of hydrogen release [7]. Ammonia borane (H3NBH3, AB) in particular has been the focus of numerous recent studies in detailing conditions for thermal [8], catalytic hydrogen release in non-aqueous solvents [9] and hydrolysis [10]. Among the three methods, the catalytic hydrolysis of AB appears to be the most convenient way [11], as it provides 3 mol of H2 per mole of AB in the presence of suitable catalyst at ambient temperature according to Eq. (1) catalyst
H3 NBH3 þ 2H2 O ! ðNH4 ÞBO2 þ 3H2
ð1Þ
The catalysts tested for hydrolysis of AB were mainly nanoparticles (NPs), in particular the noble metals such as Pd [12], Rh [13], Ir [14], Ru [12], and Pt [15], which have been identified to be effective for accelerating the hydrolytic dehydrogenation of AB. Their high price tags and limited
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