PEM Fuel Cell Catalysts Based On Platinized Graphene/Ceramics Nano-sandwich Architectures

The catalyst is one of the key components of proton exchange membrane fuel cells(PEMFCs). Graphene is widely used in fuel cell catalysts due to the excellent physical and chemical properties, such as high specific surface area, electrical conductivity, mechanical properties and good electrochemical stability. However, Graphene tends to bend and fold, this lead to reduce the utilization of Pt and the stability of the catalyst.For the first time a novel oxygen reduction catalyst with a 3D platinized graphene/nano-ceramic sandwiched architecture is successfully prepared by an unusual method. Herein the specific gravity of graphene nanosheets(GNS:~2.2 g/cm3) is tailored by platinizing graphene in advance to shorten the difference in specific gravity between carbon and nano-ceramic materials(SiC:~3.2 g/cm3), and then nano-ceramic is well intercalated into GNS interlayers. TEM?SEM?Raman?XRD?CV?LSV and EIS test of Pt-RGO/ SiC, Pt/RGO and Pt/C demonstrate the re-stacking of GNS is effectively impeded. Nano-ceramic between graphene layers can act as nanoscale spacers to prevent the aggregation of GNS and to increase the spacing between adjacent carbon nanosheets, avoiding face-to-face van der Waals contact of neighbouring nanosheets. The Pt nanoparticles of composite(Pt-RGO/SiC) with a uniform distribution shows very excellent electrochemical properties. Significantly, the electrochemical surface area(ECSA) and mass activity of the prepared catalyst is up to Pt-RGO/ SiC(112 m2 g-1 / 174 A g-1),which is more than Pt/RGO(80 m2 g-1 / 112 A g-1)and Pt/C(60 m2 g-1 / 72 A g-1). Respectively. further fuel cell tests of Pt-RGO/ SiC show a maximum power density as high as 747 mW/cm2 at low Pt loading, which is more than 2 times higher that of the pure graphene electrode.On the other hand, the new catalyst demonstrates a predominant electrochemical stability in comparison with the above catalysts as benchmarks. The great improved performance of the catalyst can be attributed to the wedge effect of nano ceramic nanoparticles and the formed unique 3D architecture that greatly decreases the re-stacking of graphene nanosheets, thereby preventing the migration and reunion of platinum particles.