PtNi Nanocrystals Supported on Hollow Carbon Spheres: Enhancing the Electrocatalytic Performance through High-Temperature Annealing and Electrochemical CO Stripping Treatments

PtNi nanoparticles have been proved to be a type of highly efficient electrocatalyst for the oxygen reduction reaction (ORR) among the Pt-based nanomaterials. However, how to improve the surface catalytic activity and stability of polymer-stabilized Pt-based nanocrystals is still a critical issue for their application in fuel cells. In this work, a one-step solvothermal process was used to synthesize PVP-stabilized PtNi nanocubes supported on hollow carbon spheres. With optimized metal precursor ratio (Pt/Ni = 1:1) and solvothermal temperature (130 °C), PtNi nanocrystals with uniform size and cubic shape can be synthesized and highly dispersed on hollow carbon spheres. To improve the electrocatalytic activity of the PtNi nanocrystals, the synthesized composite was treated by a heating annealing at 300 °C and a subsequent electrochemical CO stripping process. It was found that the two-step treatment can significantly enhance the catalytic activity of the PtNi nanocrystals for ORR with high durability. In addition, the prepared PtNi composite also showed higher catalytic activity and stability for methanol oxidation. The obtained peak current density on the present catalyst can reach 3.89 A/mg_Pt, which is 9 times as high as commercial Pt/C (0.43 A/mg_Pt). The present study not only demonstrates a general method to synthesize hollow carbon sphere-supported nanoparticle catalysts but also provides an efficient strategy to active the surface activity of nanoparticles.