Pt distribution-controlled Ni-Pt nanocrystalsviaan alcohol reduction technique for the oxygen reduction reaction

Alloying Pt with transition elements as electrodes in fuel cells has been proposed to solve the CO poisoning effect besides cost-benefit. Consequently, the use of Ni-Pt nanoparticles (NPs) has been proved to be effective among other transition metals such as Co and Fe. Though there are some reports on the synthesis of nanometer-scale particles, optimization of their composition has scarcely been reported. Thus, in this study, the influence of Pt atoms’ elemental distribution on the catalytic activities of Ni-Pt alloy NPs was investigated by measuring the oxygen reduction reaction (ORR) in acidic medium. Ni-Pt NPs with Pt concentrations between 7 and 73 at% were synthesized by an alcohol reduction methodviathe oleylamine complexation of Pt for controlling the size, shape and composition. Ni₇₄Pt₂₆alloy NPs exhibited the highest catalytic performance, and their mass and specific activities were about 5.1 and 8 times, respectively, that of the commercial Pt catalyst. Moreover, in order to enhance the stability and durability of the particles, Pt-coated Ni₇₄Pt₂₆alloy NPs were also successfully synthesized by modifying the process to facilitate the heterogeneous nucleation of Pt on the particle surface expecting coherent and ligand effects. The activity of Pt-coated Ni₇₄Pt₂₆NPs was about 2 times that of the commercially available catalyst but was almost 0.5 times that of Ni₇₄Pt₂₆particles. The durability was enhanced and comparable to that of the commercial Pt catalyst, suggesting that Pt coating on Ni-Pt alloy nanoparticles could be the design criterion for a highly reactive and cost-effective catalyst.