Herein, following a Surface Limited Redox Replacement (SLRR) few monolayers (MLs) of Pt are grown electrochemically on top of a stand-alone buckypaper. Pt thickness is controlled systematically through under potential deposition iterations and the growth was monitored by cyclic voltammetry (CV) scans. Pt MLs wet the CNT ribbons of the buckypaper, while avoiding agglomeration. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) analysis show that surface-utilization is efficient, as Pt is successively deposited not only on the near surface CNTs, but down to the bulk of buckypaper. In addition, XPS analysis shows that the Pt_MLs are in their metallic state, thus confirming successful SLRR rather than eletroless deposition (where some cationic Pt would be expected).
Catalyst longevity under processing conditions is a crucial factor to determine the lifetime of fuel cell and its price, which affects its commercialization directly. Department of Energy (DOE) sets a testing protocol to test catalyst activity loss under electrochemical testing. DOE protocols’ target to save 60% of the catalyst activity by 30,000 testing cycles. Our Pt_MLs/buckypaper catalysts show promising results, while saving 50% of the catalyst activity as shown through linear sweep voltammetry (LSV) currents for oxygen reduction reaction (ORR). Raman analysis shows no alteration of CNT G and 2D bands after 30,000 testing cycles, in comparison to Raman spectra of the same sample set before testing, which indicates no carbon corrosion.
In conclusion, no carbon corrosion is observed for CNT after long testing (i.e. 30,000 cycles). In addition, power density of Pt MLs catalysts is enhanced by wetting-ability of Pt to the buckypaper throughout its internal 3D porous structure. Moreover, buckypaper shows high susceptibility to Pt interfacial adhesion, and the interfacial interaction between Pt and CNT surface helps to retain Pt atoms as 2D film without ripening. Catalyst activity retained after 30,000 testing cycles is ~ 50%. This initial result promises with more enhancement for power density and catalyst lifetime with chemical functionalization of CNTs in our future work.