Promotion of Oxygen Reduction with Both Amorphous and Crystalline MnOx through the Surface Engineering of La0.8Sr0.2MnO3- Perovskite

Surfaces play a key role in catalysis. Surfaces can be modified in a number of ways, for example by depositing nanoparticles or with functional coating layers. Here, the surface of La0.8Sr0.2MnO3- (LSMO) is treated with diluted HNO3. This process leads to the preferential formation of MnOx/LSMO on the surface, leading to the exposure of Mn cations at the surface of LSMO. The electrocatalytic activity of the MnOx/LSMO heterostructure towards the oxygen reduction reaction (ORR) is shown to increase when it is compared to the untreated LSMO. Thanks to the formation of MnOx at the surface, the resulting MnOx/LSMO possesses 1) a relatively high specific surface area and a mesoporous structure, 2) a higher coverage of Mn4+/Mn3+ cations at the surface, and 3) a high concentration of highly oxidative oxygen species. This work develops a facile strategy (i.e. HNO3 treatment) for improving the ORR activity of perovskite oxides in alkaline solution at room temperature.