Heteroatom-doped nanomaterials/core–shell nanostructure based electrocatalysts for the oxygen reduction reaction

Abstract

Recently, heteroatom doped core–shell nanostructures (HCSNs) have been widely used as superior electrocatalysts for the oxygen reduction reaction (ORR) owing to their enhanced ORR performance and stability under harsh environmental conditions. In this review, we provide the importance of HCSNs and explain how the ORR performance can be enhanced by various heteroatom dopants, such as nitrogen, sulfur, phosphorous, boron, and combinations of two or more heteroatoms. Various types of nitrogen doping were performed with different forms of nitrogen-containing organic compounds in CSNs, such as metal–organic frameworks, zeolitic imidazolate frameworks, and transition metals containing nitrogen sources, which have been used widely for the ORR because they form a high surface area, a facet surface structure, and reactive active sites in the presence of elements that are useful for the ORR catalytic activity. Furthermore, we briefly discuss the synthesis and fabrication of highly efficient ORR electrodes using a combination of di-, tri-, or multi-heteroatom-doped CSNs. Finally, we discuss the superior ORR activities of the HCSNs reported in recent literature and compare the activity with various reactive descriptors and the broad scope of these HCSNs for practical applications, along with their drawbacks and future demands.