Synthesis Of Fe,Ni And Fe/Ni Nanoparticles And Their Catalytic Activity For Hydrogen Generation From KBH₄

Liquid-phase chemical hydrogen storage materials have been extensively investigated based on their safe and environmentally benign route to the production of hydrogen.Metal nanoparticles（NPs）can act as highly effective catalysts for the hydrolysis of potassium borohydride（KBH₄）which is a kind of liquid phase chemical hydrogen storage materials.ISOBAM-104 protected Fe,Ni monometallic NPs and Fe/Ni bimetallic nanoparticles（BNPs）were prepared by chemical reduction method in this paper.These prepared NPs are used for the hydrolysis of KBH₄ and characterized by ultraviolet-visible spectrophotometry（UV-Vis）,transmission electron microscopy（TEM）,high-resolution transmission electron microscopy（HRTEM）,X-ray photoelectron spectroscopy（XPS）and double cs-corrected TEM.The influence of molar ratio of ISOBAM to metal ions(R_ISO),the concentration of metal ions（C_M）and various protectors on the catalytic performance were investigated and apparent activation energy（E_a）of the hydrolysis of KBH₄ was also calculated.All the results suggested that:（1）Small sized and uniformly distributed Fe NPs were prepared using ISOBAM-104 as protective agent and Fe（NO₃）₃·9H₂O as precursors with R_ISO and C_Fe3+within the range of 20 to 80,0.3 mM to 0.7mM respectively.The results of UV-Vis suggested that Fe NPs were oxidized into Fe³⁺gradually with storage time prolonging.The average diameter of Fe NPs prepared was only 1.9 nm under the condition of R_ISO=40,C_Fe3+=0.6 mM.The corresponding catalytic activity for hydrolysis of KBH₄ of Fe NPs was 8100 ml-H₂·min^-1·g-Fe^-1.Fe NPs showed a low apparent energy of 44.9±5.9 kJ/mol for the hydrolysis of an alkaline KBH₄.（2）Small sized and uniformly distributed Ni NPs were prepared using ISOBAM-104 as protective agent and Ni（NO₃）₂·6H₂O as precursors respectively with R_ISO and C_Ni2+within the range of 30 to 70 and 0.3 mM to 1.2 mM.Ni NPs were oxidized into Ni²⁺gradually with storage time prolonging.The average diameter of Ni NPs prepared under the condition of R_ISO=50 and C_Ni2+=0.6 mM was only 1.8 nm,the catalytic activity of Ni NPs for hydrolysis of KBH₄ was 12400 ml-H₂·min^-1·g-Ni^-1.Ni NPs showed a low apparent energy of 29.6 kJ/mol for the hydrolysis of an alkaline KBH₄.（3）Small sized and uniformly distributed Fe/Ni BNPs were prepared using ISOBAM-104 as protective agent,Fe（NO₃）₃·9H₂O and Ni（NO₃）₂·6H₂O as precursors The average diameter of as-prepared Fe/Ni BNPs was between 2 nm and 4 nm.The results suggested that the prepared Fe₁₀Ni₉₀0 BNPs showed the highest catalytic activity of 11600 ml-H₂·min^-1·g-M^-1.Fe₁₀Ni₉₀ BNPs showed the apparent energy of36.9±1.9 kJ/mol for the hydrolysis of an alkaline KBH₄.