Crystal facet-dependent activity of α-Mn2O3 for oxygen reduction and oxygen evolution reactions

Electrocatalysts with different morphologies and specific exposed facets usually exhibit distinguished activities. In this work, two alpha-Mn2O3 with different morphologies and crystal facets were successfully prepared by solvothermal method and investigated as ORR/OER bifunctional catalysts for the first time. The results showed that the catalytic performance is affected by the crystal facet of alpha-Mn2O3, and the alpha-Mn2O3-cubic has better bifunctional activity than alpha-Mn2O3-octahedra. As revealed by catalyst characterization, the enhanced activity is originated with the nature of the exposed alpha-Mn2O3 (100) facet. The (100) facet with abundant low-coordinated surface oxygen sites makes the formation of more oxygen vacancies, which can improve the charge transfer and optimize the adsorption energies for intermediates, thereby enhancing the bifunctional activity for ORR/OER. This work high-lights the correlation between OER/ORR activities and exposed crystal planes of alpha-Mn2O3 catalysts and it may deepen the understanding of facetdependent activity of alpha-Mn2O3 and points out a strategy to improve their catalytic activity by crystal facet engineering. (c) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.