Transition Metal-Doped Nanocarbon Electrocatalysts for Oxygen Reduction Reaction

Oxygen reduction reaction (ORR) is the cathode half-reaction occurring in devices like proton/anion exchange membrane fuel cells and metal-air batteries. Developing non-precious metal-based catalytic systems for these advanced energy conversion and storage devices is crucial for their commercialization and elimination of the dependence on noble metal catalysts. The transition metallic active sites in these electrocatalysts are required to be well-dispersed across the suitable electrically conducting carbon support matrices, which facilitate efficient electron and gas flow channels as required for the charge and mass transport, respectively. The hierarchical porous heteroatom doped electrically conductive carbon support can effectively serve this purpose. The morphology of these catalyst systems significantly affects the electrochemical performance. This motivated the exploration of core-shell and atomically-dispersed transition metal-carbon ORR catalysts in recent literature. Further, the proper understanding of the synergism between different components of the devices and involved degradation mechanisms leading to performance loss is of utmost importance. This has led to note-worthy improvement in designing and performing these transition metal ORR catalysts, as evident from their employment in commercial devices.