Preparation and catalytic activity of PVP-protected Au/Ni bimetallic nanoparticles for hydrogen generation from hydrolysis of basic NaBH4 solution

• PVP-protected Au/Ni BNPs with size of 2.0 ± 0.7 nm in diameter were synthesized.
• Catalytic activity of Au/Ni BNPs for hydrogen generation from NaBH4 was studied.
• Catalytic activity of Au50Ni50 BNPs is 9 times higher than that of Au MNPs.
• DFT and XPS proved the negatively charged Au atoms and positively charged Ni atoms.
• The corresponding apparent activation energy was 30.3 kJ/mol for the Au50Ni50 BNPs.

Poly(N-vinyl-2-pyrrolidone)(PVP)-protected Au/Ni bimetallic nanoparticles (BNPs) were prepared in one-vessel via chemical reduction of the corresponding ions with dropwise addition of NaBH4, and their catalytic activity in the hydrogen generation from hydrolysis of a basic NaBH4 solution was examined. The structure, particle size, and chemical composition of the resultant BNPs were characterized by Ultraviolet–visible spectrophotometry (UV–Vis), X-ray photoelectron spectroscopy (XPS), Transmission electron microscopy (TEM) and High-resolution transmission electron microscopy (HR-TEM). The effects of processing parameters such as metal composition, metal ion concentration, and mole ratio of PVP to metal ion on the hydrolysis of a basic NaBH4 solution were studied in detail. The results indicated that as-prepared Au/Ni BNPs showed a higher catalytic activity than corresponding monometallic NPs (MNPs) in the hydrogen generation from the hydrolysis reaction of a basic NaBH4 solution. Among all the MNPs and BNPs, Au/Ni BNPs with the atomic ratio of 50/50 exhibited the highest catalytic activity, showing a hydrogen generation rate as high as 2597 mL-H2 min−1 g-catalyst−1 at 30 °C, which can be ascribed to the presence of negatively charged Au atoms and positively charged Ni atoms. Based on the kinetic study of the hydrogen generation from the hydrolysis reaction of a basic NaBH4 solution over the PVP-protected Au/Ni BNPs, the corresponding apparent activation energy was determined as 30.3 kJ/mol for the BNPs with the atomic ratio of 50/50.

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