RESUMEN
Platinum-based catalysts are widely used for efficient catalysis of the acidic oxygen reduction reaction (ORR). However, the agglomeration and leaching of metallic Pt nanoparticles limit the catalytic activity and durability of the catalysts and restrict their large-scale commercialization. Therefore, this study aimed to achieve a uniform distribution and strong anchoring of Pt nanoparticles on a carbon support and improve the ORR activity and durability of proton-exchange membrane fuel cells. Herein, we report on the facile one-pot synthesis of a novel ORR catalyst using metal-nitrogen-carbon (M-N-C) bonding, which is formed in situ during the ion exchange and pyrolysis processes. An ion-exchange resin was used as the carbon source containing R-N+(CH3)3 groups, which coordinate with PtCl62- to form nanosized Pt clusters confined within the macroporous framework. After pyrolysis, strong M-N-C bonds were formed, thereby preventing the leaching and aggregation of Pt nanoparticles. The as-synthesized Pt supported on the N-doped hierarchically porous carbon catalyst (Pt/NHPC-800) showed high specific activity (0.3 mA cm-2) and mass activity (0.165 A mgPt-1), which are approximately 2.7 and 1.5 times higher than those of commercial Pt/C, respectively. The electrochemical surface area of Pt/NHPC-800 remained unchanged (~1% loss) after an accelerated durability test of 10,000 cycles. The mass activity loss after ADT of Pt/NHPC-800 was 18%, which is considerably lower than that of commercial Pt/C (43%). Thus, a novel ORR catalyst with highly accessible and homogeneously dispersed Pt-N-C sites, high activity, and durability was successfully prepared via one-pot synthesis. This facile and scalable synthesis strategy for high-efficiency catalysts guides the further synthesis of commercially available ORR catalysts.
RESUMEN
Electrocatalysts for the oxygen reduction reaction (ORR) are crucial in metal-air batteries, fuel cells and other electrochemical devices. In this study, iron and nitrogen co-doped carbon sphere electrocatalysts were synthesized by electrospinning and thermal treatment. According to the results, the catalyst marked as Fe-N/MCS-181 (Fe, N-doped mesoporous carbon spheres, iron nitrate nonahydrate as the iron source) has not only the highest iron content, which reaches up to 0.13%, but also a spherical shape. And its pore sizes are 11 and 35 nm. For the electrochemical performance, the onset potential (E onset) of Fe-N/MCS-181 is -0.018 V, while the half-wave potential (E 1/2) of Fe-N/MCS-181 is -0.145 V, which is better than the commercial Pt/C catalyst (E 1/2 is -0.18 V). The durability of the Fe-N/MCS-181 catalyst is better than commercial Pt/C. After 10 000 s, the retention ratio of current density is 86.4%, while that of the commercial Pt/C catalyst is 84.2%. At the same time, the methanol tolerance of the Fe-N/MCS-181 catalyst is also excellent. After adding methanol, the current density of the Fe-N/MCS-181 catalyst has no obvious change. This study provides an easy method to fabricate a highly efficient and durable Fe, N-doped carbon catalyst for the oxygen reduction reaction.
RESUMEN
Nitrogen-doped reduced graphene oxide-metal(metal oxides) nanoparticle (N-rGO-M(MO) NPs, M = Fe, MO: M = Co, Mn) composites were prepared through a facile and general method at high temperature (800 °C). M(MO) were well-dispersed and tightly anchored on graphene sheets, which were doped with nitrogen simultaneously and further loaded with Pt nanoparticles. Those results showed a more positive onset potential, higher cathodic density, and higher electron transfer number for the ORR in alkaline media. Furthermore, N-rGO-metal(metal oxides)-Pt (N-rGO-M(MO)-Pt) nanoparticles show better durability than the commercial Pt/C catalyst, and can be used as promising potential materials in practical applications.