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Bifunctional α ‐MnO 2 and Co 3 O 4 Catalyst for Oxygen Electrocatalysis in Alkaline Solution
Author(s) -
Fink Michael F.,
Eckhardt Julia,
Khadke Prashant,
Gerdes Thorsten,
Roth Christina
Publication year - 2020
Publication title -
chemelectrochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.182
H-Index - 59
ISSN - 2196-0216
DOI - 10.1002/celc.202001325
Subject(s) - bifunctional , catalysis , electrocatalyst , oxygen evolution , nanoparticle , oxygen , materials science , bifunctional catalyst , chemistry , chemical engineering , inorganic chemistry , nanotechnology , electrochemistry , electrode , organic chemistry , engineering
Low cost and abundant catalysts demonstrating high activity and stability towards the oxygen reactions, i. e., the oxygen reduction (ORR) and oxygen evolution reaction (OER), are crucial for the development of electrically rechargeable zinc‐air batteries. Herein, the facile synthesis and systematic characterisation of two highly active and stable oxygen electrocatalysts, i. e., high surface area α ‐MnO 2 microspheres and nanoparticulate Co 3 O 4 , are reported. α ‐MnO 2 exhibits low half‐wave potential and potential of −0.197 and −0.226 V (vs. Ag/AgCl) at −3 mA cm −2 , respectively, that are only marginally higher compared to commercial Pt/C ( E 1/2 =−0.161 V, E j =‐3 =−0.171 V) for ORR. Meanwhile, Co 3 O 4 needs a potential of 0.601 V (vs. Ag/AgCl) to drive 10 mA cm −2 being competitive to commercial Ir/C ( E j =10 =0.60 V) for OER. In order to create a bifunctional catalyst, two approaches were pursued: i) Co 3 O 4 nanoparticles were homogeneously grown on the surface of α ‐MnO 2 microspheres yielding a radial hybrid composite catalyst material in the form of a core ( α ‐MnO 2 ) shell (Co 3 O 4 ) structure and ii), much simpler, individual α ‐MnO 2 microspheres and Co 3 O 4 nanoparticles were physically mixed in a powder blend. The powder blend demonstrates superior overall bifunctional catalytic properties such that the individual catalysts still dominate their respective oxygen reaction and, due to synergistic interactions between both catalysts, an improved ORR activity could be achieved.