Reported here is a facile route for the synthesis of polyvinyl pyrrolidone (PVP)-stabilized Pd/Co bimetallic nanoparticles via a chemical co-reduction process. The effects of molar ratio of PVP and reducing reagent (NaBH4) to the total metal ions, and metal ion concentration and composition on the catalytic activity for hydrogen generation from NaBH4 over Pd/Co bimetallic nanoparticles (BNPs) were studied. The transmission electron microscopy (TEM) results indicated that the prepared Pd/Co bimetallic nanoparticles, which had an average size of 1.5-2.8 nm, showed much higher catalytic activity than Pd and Co monometallic nanoparticles (MNPs). The highest catalytic activity of all the prepared bimetallic nanoparticles was 15570 mol.mol(-1).h(-1) (the activity was normalized by the content of Pd in the BNPs), which was achieved with Pd/Co theoretical atom ratio of 1/9. The higher catalytic activity of the Pd/Co BNPs compared with the corresponding MNPs was ascribed to electronic charge transfer effects; this hypothesis was validated using density functional theory (DFT) calculations, which showed that the Pd atoms were indeed negatively charged, while the Co atoms were positively charged because of electron donation from the Co atoms to the Pd atoms. The positively charged Co atoms and negatively charged Pd atoms acted as catalytic active sites for the hydrolysis reaction of the alkaline NaBH4 solution. Good catalytic stability was observed with the existing high catalytic activity, even after five runs of evaluating the catalytic activity. Moreover, no clear agglomeration was observed in the nanoparticle catalyst used. The corresponding apparent activation energy was determined as 54 kJ.mol(-1), based on the kinetic study of the hydrogen generation achieved via the NaBH4 hydrolysis over the PVP-protected Pd10Co90 bimetallic nanoparticles.

采用化学共还原法合成了聚乙烯吡咯烷酮保护的Pt/Cu双金属纳米颗粒(BNPs),并采用紫外可见吸收光谱、透射电子显微镜、高分辨透射电子显微镜等对所合成的Pt/Cu BNPs进行了表征.研究了化学组成对Pt/Cu BNPs催化NaBH4水解制氢性能的影响.结果表明,所制备的Pt/Cu BNPs平均粒径为1.8～2.3nm,其催化活性远高于单金属Pt和Cu NPs的活性,其中Pt90 Cu10 BNP的催化活性最高,其在30℃的条件下,催化NaBH4制氢的活性可达6570mol-H2·mol-cat-1·h-1,约为相同粒径的Pt单金属NP的1.6倍.密度泛函理论的计算结果表明,Pt/Cu BNPs优异的催化性能可归因子电荷转移效应,Pt原子与Cu原子之间发生的电子转移使得Pt原子带负电而Cu原子带正电,荷电的Pt和Cu原子成为催化反应的活性中心.

Poly-(N-vinyl-2-pyrrolidone) (PVP)-protected Pt/Ni/Fe trimetallic nanoparticles (TNPs) were prepared using a chemical co-reduction method. The obtained TNPs were characterized by transmission electron microscopy(TEM). The effects of metal compositions on the hydrolysis reaction of the alkaline NaBH4 solution were studied. The results indicated that the prepared Pt/Ni/Fe TNPs had an average size of 2 nm. The activities of TNPs were much higher than that of Fe, Ni and Pt monometallic nanoparticles (MNPs) and Ni/Fe, Pt/Fe and Pt/Ni bimetallic nanoparticles (BNPs). Among all the synthesized MNPs, BNPs and TNPs, Pt/Ni/Fe TNPs with molar ratio of 10 : 78.75: 11.25 displayed the highest catalytic activity, showing a high hydrogen release rate of 63.920x10(3) mol(H2)/(mol(Pt).h) at 30 degrees C. The corresponding apparent activation energy for the hydrolysis reaction of the alkaine NaBH4 solution over the Pt10Ni87.75Fe11.25 TNP is about 52 kJ/mol. In addition, the prepared Pt/Ni/Fe TNPs had a good catalytic stability, which kept a high activity even after 10-run catalytic evaluation.