One-step pyrolysis method for the synthesis of highly efficient 3D hollow carbon nanostructure supported metallic catalysts

By using a one-step pyrolysis method, porous hollow carbon nanosphere supported PtRu catalysts are synthesized from the metallic salt-adsorbed hollow polymer (i.e. chitosan) nanosphere complex. The hollow polymer structure acts as both the template and the carbon precursor for the hollow structure fabrication, provides sites for dispersing metallic precursors and subsequent nucleation centers for catalyst deposition in the pyrolysis process. TEM, XRD, and XPS measurements show that formation of metallic nanoparticles and carbon support occurs simultaneously in the pyrolysis process, the resultant carbon nanospheres have porous hollow core-shell structure, and the loaded catalyst has high PtRu alloying degree. In addition, the present approach allows us to finely adjust the loading and bulk composition of PtRu particles by changing the concentration and atomic ratio of the metallic solutions for salt adsorption, and the particle size of PtRu can be well controlled to less than 10 nm. Electrochemical results show that the prepared catalyst (with 18.5%wt Pt and the atomic ratio of Pt/Ru = 1:1) shows high electrochemical activity and stability toward the oxidation of methanol, even outperforming the commercial PtRu/XC-72 (JM) catalyst. This excellent performance could be due to the unique structure of carbon nanostructure and the pyrolysis-method-induced high stability and alloying degree of the loaded metallic catalysts.