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Impact of carbon N-doping and pyridinic-N content on the fuel cell performance and durability of carbon-supported Pt nanoparticle catalysts

Hornberger, Elisabeth; Merzdorf, Thomas; Schmies, Henrike; Hübner, Jessica; Klingenhof, Malte; Gernert, Ulrich; Kroschel, Matthias; Anke, Björn; Lerch, Martin; Schmidt, Johannes; Thomas, Arne; Chattot, Raphaël; Martens, Isaac; Drnec, Jakub; Strasser, Peter

FG Anorganische Chemie - Festkörper- und Materialchemie

Cathode catalyst layers of proton exchange membrane fuel cells (PEMFCs) typically consist of carbon-supported platinum catalysts with varying weight ratios of proton-conducting ionomers. N-Doping of carbon support materials is proposed to enhance the performance and durability of the cathode layer under operating conditions in a PEMFC. However, a detailed understanding of the contributing N-moieties is missing. Here, we report the successful synthesis and fuel cell implementation of Pt electrocatalysts supported on N-doped carbons, with a focus on the analysis of the N-induced effect on catalyst performance and durability. A customized fluidized bed reduction reactor was used to synthesize highly monodisperse Pt nanoparticles deposited on N-doped carbons (N–C), the catalytic oxygen reduction reaction activity and stability of which matched those of state-of-the-art PEMFC catalysts. Operando high-energy X-ray diffraction experiments were conducted using a fourth generation storage ring; the light of extreme brilliance and coherence allows investigating the impact of N-doping on the degradation behavior of the Pt/N–C catalysts. Tests in liquid electrolytes were compared with tests in membrane electrode assemblies in single-cell PEMFCs. Our analysis refines earlier views on the subject of N-doped carbon catalyst supports: it provides evidence that heteroatom doping and thus the incorporation of defects into the carbon backbone do not mitigate the carbon corrosion during high-potential cycling (1–1.5 V) and, however, can promote the cell performance under usual PEMFC operating conditions (0.6–0.9 V).