Au/Ni双金属纳米颗粒的制备及其催化制氢活性

Preparation and Catalytic Activity of Au/Ni Bimetallic Nanoparticles for Hydrogen Generation from the Hydrolysis Reaction of Alkaline NaBH4 Solution

摘要:

采用化学共还原法制备了聚乙烯吡咯烷酮(PVP)保护的Au/Ni双金属纳米颗粒，采用UV-Vis、TEM对所合成的纳米颗粒进行了表征，研究了双金属纳米颗粒的化学组成对其催化水解NaBH4制氢活性的影响。结果表明：所制备的Au/Ni双金属纳米颗粒的平均粒径为2.9~4.2 nm，Au/Ni双金属纳米颗粒的催化活性高于Au和Ni单金属纳米颗粒的活性，Au50Ni50双金属纳米颗粒的催化活性最高，30 ℃时其催化活性数值达到550 mol-H2·h-1·mol-M-1。XPS和密度泛函理论(DFT)的结果都表明：Au/Ni双金属纳米颗粒优异的催化性能可归因于电荷转移效应，Ni原子与Au原子之间发生的电子转移使得Au原子带负电而Ni原子带正电，荷电的Au和Ni原子成为催化反应的活性中心。Au50Ni50双金属纳米颗粒催化水解NaBH4制氢的活化能为61.9 kJ/mol。

Abstract:

Poly(N-vinyl-2-pyrrolidone) (PVP)-protected Au/Ni bimetallic nanoparticles (BNPs) were prepared using a chemical reduction method. The obtained BNPs were characterized by Ultraviolet-visible spectrophotometry (UV-Vis) and transmission electron microscopy (TEM). The effects of metal compositions on the hydrolysis reaction of the alkaline NaBH4 solution were studied. The results indicate that the prepared Au/Ni BNPs have an average size of 2.9~4.2 nm. The activities of BNPs are much higher than that of Au and Ni monometallic nanoparticles (MNPs). Among all the MNPs and BNPs, Au/Ni BNPs with atomic ratio of 50/50 display the highest catalytic activity, showing a high hydrogen release rate of 550 mol-H2·h-1·mol-M-1 at 30 oC. The catalytic activity of the Au/Ni BNPs higher than that of corresponding MNPs can be ascribed to electronic charge transfer effects. X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) show that Au atoms are indeed negatively charged, while the Ni atoms have positive charges due to the electron donation from the Ni atoms to Au atoms. The positively charged Ni atoms and negatively charged Au atoms act as catalytic active sites for the hydrolysis reaction of the alkaline NaBH4 solution. Au50Ni50 BNPs display a low apparent activation energy of 61.9 kJ/mol.