Insight into the Mechanism of Oxygen Reduction Reaction on Micro/Mesoporous Carbons: Ultramicropores versus Nitrogen-Containing Catalytic Centers in Ordered Pore Structure

BARRERA, DEICY; FLORENT, MARC; SAPAG, KARIM; BANDOSZ, TERESA J.

ACS Applied Energy Materials

ACS

Año: 2019 vol. 2 p. 7412 - 7424

2574-0962

Ordered mesoporous/microporous carbon wassynthesized from sucrose. The carbon was oxidized andmodified with urea at 600, 800, and 950 °C. The obtainedcarbons differed in the pore size distributions in the meso- andmicropore ranges. The carbons, after an extensive surfacecharacterization, were used as ORR catalysts in a KOHelectrolyte. Kinetic current densities and n reached 12.5 mAcm−2 and 3.94, respectively. The results suggested that smallmicropores increased the efficiency of ORR. The density ofsurface oxygen in mesopores had also a positive effect on ORRby increasing the hydrophilicity and the electrochemicallyactive surface area (ECSA) and, thus, the accessibility ofoxygen dissolved in the electrolyte to the pores of the highest adsorption potential. From the viewpoint of the number ofelectron transfers, current density, and onset potential, the carbons with small pore sizes and with only traces of nitrogenperformed equally, or even better, in ORR process as those containing the catalytic nitrogen sites.