Solvothermal Synthesis of Nanostructured PtnNi Tetrahedrons with Enhanced Platinum Utilization and Activity toward Oxygen Reduction Electrocatalysis

Well-faceted alloyed Pt nanoparticles (NPs) have been widely investigated as promising electrocatalysts with impressively high activity for oxygen reduction reaction (ORR). Reducing the size of such well-faceted NPs would be anticipated to enhance the utilization efficiency but lower the intrinsic activity of Pt. It is thus crucial to balance between the Pt utilization and its intrinsic activity. Herein, relatively small PtnNi nanotetrahedrons (4-5 nm, n refers to the Pt/Ni ratio in the metal precursors) were synthesized by one-pot solvothermal synthesis in N,N-dimethylformamide using form-aldehyde as an additive and polyvinylpyrrolidone as a stabilizer. The as-synthesized PtnNi NPs were then immobilized on carbon to make PtnNi/C catalysts for cathode ORR. Among these PtnNi/C samples, Pt3Ni/C shows up as the most active Pt catalyst, whose intrinsic (IA(Pt)) and mass-specific activity (MSA(Pt)) numbers are ca. 6.7- and 5.8-fold higher than those for commercial Pt/C (20% Pt, E-TEK), respectively. Pt1Ni/C is also distinctive, showing an EAS(Pt) as high as 82 m(2) g(Pt)(-1) and IA(Pt) and MSA(Pt) numbers of 4-5 folds higher than those for the Pt/C. The significantly enhanced Pt activity in the PtnNi tetrahedrons would arise from combined effects of their small sizes and Pt-enrichment at the surface layers after the electrochemical (dealloying) treatment.

Automated summary

Well-faceted alloyed Pt nanoparticles have been synthesized, with Pt3Ni/C showing the highest Pt activity and Pt1Ni/C also exhibiting significant activity. The enhanced Pt activity in the PtnNi tetrahedrons is attributed to their small sizes and Pt-enrichment at the surface layers after dealloying treatment.