Activating Nitrogen-doped Graphene Oxygen Reduction Electrocatalysts in Acidic Electrolytes using Hydrophobic Cavities and Proton-conductive Particles.

Although pyridinic-nitrogen (pyri-N) doped graphene is highly active for the oxygen reduction reaction (ORR) of fuel cells in alkaline media, the activity critically decreases under acidic conditions. We report on how to prevent the deactivation based on the mechanistic understanding that O 2 + p y r i - N H + + e - → O 2 , a + p y r i - N H ${{{\rm O}}_{2}+{\rm p}{\rm y}{\rm r}{\rm i}{\rm { -}}{\rm N}{{\rm H}}^{+}+{{\rm e}}^{-}{\to }_{\ }^{{\rm \ }}{{\rm O}}_{2,{\rm a}}+{\rm p}{\rm y}{\rm r}{\rm i}{\rm { -}}{\rm N}{\rm H}}$ governs the ORR kinetics. First, we considered that the deactivation is due to the hydration of pyri-NH+ , leading to a lower shift of the redox potential. Introducing the hydrophobic cavity prevented the hydration of pyri-NH+ but inhibited the proton transport. We then increased proton conductivity in the hydrophobic cavity by introducing SiO2 particles coated with ionic liquid polymer/Nafion® which kept the high onset potentials with an increased current density even in acidic media. © 2022 Wiley-VCH GmbH.

Citation

Santosh K Singh, Kotaro Takeyasu, Kaito Homma, Shigeharu Ito, Takashi Morinaga, Yuto Endo, Moeko Furukawa, Toshiyuki Mori, Hirohito Ogasawara, Junji Nakamura. Activating Nitrogen-doped Graphene Oxygen Reduction Electrocatalysts in Acidic Electrolytes using Hydrophobic Cavities and Proton-conductive Particles. Angewandte Chemie (International ed. in English). 2022 Dec 19;61(51):e202212506

PMID: 36240783

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