Insight into the performance and stability of N-doped Ordered Mesoporous Carbon Hollow Spheres for the ORR: Influence of the nitrogen species on their catalytic activity after ADT

Novel N-doped Ordered Mesoporous Carbon Hollow Spheres (N-OMCHS) were successfully synthetized using two different nitrogen sources: i) 2-pyridinecarboxaldehyde (labeled as N1-OMCHS), and ii) pyrrole (labeled as N2-OMCHS). The catalytic activity of the synthesized N-OMCHS was evaluated towards the Oxygen Reduction Reaction (ORR) in alkaline media. Likewise, the effect of Accelerated Degradation Test (ADT) on the stability of the N-OMCHS was discussed. N2-OMCHS showed the best performance for the ORR (E-onset = 0.88 V, E-1/2 = 0.82 V, H2O2 yield = 3.8% and n = 3.92, all potentials vs. RHE). Surprisingly, after evaluating the stability of each electrocatalyst by ADT, it was observed that the performance of N1-OCMHS improved with respect to that evaluated before ADT. N1-OCMHS had a better stability compared to N2-OMCHS. X-ray photoelectron spectroscopy (XPS) results before and after ADT demonstrated the chemical modification of nitrogen species on the surface of the electrocatalysts, which influenced a better performance towards the ORR. Therefore, N-OMCHS were considered as potential non-platinum electrocatalysts for Anion Exchange Membrane Fuel Cells (AEMFC) cathode applications. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

Novel N-doped ordered mesoporous carbon hollow spheres (N-OMCHS) were successfully synthesized using two different nitrogen sources, N1-OMCHS and N2-OMCHS, and their catalytic activity towards the Oxygen Reduction Reaction (ORR) in alkaline media was evaluated. N2-OMCHS showed the best performance for the ORR, but surprisingly, N1-OMCHS improved in performance after Accelerated Degradation Test (ADT) and exhibited better stability compared to N2-OMCHS. X-ray photoelectron spectroscopy results indicated chemical modifications of nitrogen species on the surface, leading to enhanced ORR performance. Therefore, N-OMCHS are considered as potential non-platinum electrocatalysts for Anion Exchange Membrane Fuel Cells (AEMFC) cathode applications.