Platinum catalysts protected by N-doped carbon for highly efficient and durable polymer-electrolyte membrane fuel cells

The Pt/C catalysts covered with nitrogen-doped carbon layers improve both ORR activity and durability. When the catalysts are applied to the cathode of the PEMFCs, the cell performance and durability were significantly enhanced even at 120 °C with 40% of the relative humidity. [Display omitted] ⿢The Pt/C catalysts protected by N-doped carbons show high activity and durability for oxygen-reduction reactions.⿢The optimum thickness of the N-doped carbon layers is ⿼1nm.⿢The Pt/C catalysts with 1 nm-thick N-doped carbon layers exhibit the best activity and durability in the PEMFC tests when annealed at 500°C.⿢The pyridinic N in the NC layers may be strongly related to the enhancement of the PEMFC performances. Precious metals such as platinum are commonly used in polymer-electrolyte membrane fuel cells (PEMFCs) to enhance sluggish oxygen-reduction reactions. However, agglomerations of the nano-sized platinum and corrosions of the carbon supports degrade the performance and durability of the PEMFC during the long-term operation. Here, we present a highly active and durable catalyst for the oxygen-reduction reactions by covering carbon-supported platinum with nitrogen-doped carbons as a protective layer. The PEMFC with the NC-protected Pt/C cathode shows a power density of 1.06Wcm⿿2 at 0.6V in H2-O2, comparable with 0.67Wcm⿿2 of the PEMFC with a commercial Pt/C cathode. Furthermore, the durability is remarkably enhanced over 50%, compared with the commercial carbon-supported platinum cathode. It suggests that the nitrogen-doped carbons as a protective layer are effective in enhancing the catalytic activity for oxygen-reduction reactions and durability of the PEMFCs.