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

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.