Highly Active Nanocatalysts for Oxygen Reduction Reaction

Abstract

The rapidly increasing energy demand for human activities stimulates the lasting research interests to develop renewable energy alternatives worldwide. The electrochemical reduction of oxygen is one of key steps in controlling the performance of various next-generation energy conversion and storage devices, such as fuel cells, metal-air batteries. The electrochemical reduction of oxygen is one of key steps in controlling the performance of various next-generation energy conversion and storage devices, such as fuel cells, metal-air batteries. The commercialization of these technologies prominently depends on the development of low-cost high-performance electrocatalysts for oxygen reduction reaction (ORR) to replace the precious metal-based catalysts. In this presentation, several reasonable ways for designing new low-cost nanocatalysts with high electrocatalytic activities and superior stability for ORR will be discussed. By focusing on the creation and the enrichment of highly active sites for ORR and simultaneously considering the mass transfer and electron transportation, we have developed several efficient ORR nanocatalysts.1-7 The further improvement of the performance can be achieved by introducing transition metal or nanostructures into these nanocatalysts. Furthermore, understanding the origin of high activity of these electrocatalysts in ORR is also critical for developing efficient non-precious metal catalysts but still challenging. We developed a new highly active Fe-N-C ORR catalyst containing Fe-Nx coordination sites and Fe/Fe3C nanocrystals, and revealed the origin of its activity by intensively investigating the composition and the structure of the catalyst and their correlations with the electrochemical performance. Based on our experimental and theoretical results, it can be concluded that the high ORR activity in this type of Fe-N-C catalysts should be ascribed to that Fe/Fe3C nanocrystals boost the activity of Fe-Nx. These new findings open an avenue for the rational design and bottom-up synthesis of low-cost highly active ORR electrocatalysts.