Electrochemical Stability of Platinum Nanoparticles Supported on N-Doped Hydrothermal Carbon Aerogels as Electrocatalysts for the Oxygen Reduction Reaction

Sustainable N-doped carbon aerogels were synthesized by a scalable hydrothermal approach using low-cost and abundant precursors such as glucose and ovalbumin. By adjusting the pyrolysis temperature (900-1500 degrees C), the surface chemistry, porosity and conductivity of these aerogels could be optimized for the design of Pt-based oxygen reduction reaction (ORR) catalysts with high Pt loading (40 wt % Pt) and improved stability. Pt nanoparticle deposition was realized by wet impregnation followed by thermal reduction and their size and distribution was found to strongly depend on the surface chemistry of the carbon aerogels. The catalysts' activities and stabilities, determined by rotating disc electrode measurements in HClO4, were found to strongly depend on the pyrolysis temperature of the N-doped carbon aerogel supports. While the mass activity decreased with increasing temperature, in line with a decreasing ECSA related to an increase in Pt nanoparticle size, the long-term stability of the catalysts, as revealed by accelerated stress tests for carbon support degradation (10,000 cycles), increased with increasing pyrolysis temperature, in line with increasing Pt nanoparticle sizes and increasing graphitization of the carbon aerogel supports. Most importantly, the catalyst derived from aerogels pyrolyzed at 1000 degrees C achieved a good compromise between activity and stability and revealed a superior ORR activity after the accelerated stress test in comparison to a commercially available Pt/C reference catalyst (40 wt % Pt).