Exposed N and S Active Sites: An Indicator for Oxygen Reduction on Metal-Free Yam-Derived Porous Carbons

摘要

Exploring efficient and low-cost catalysts for the oxygen reduction reaction (ORR) is a key issue in the development of renewable energy devices such as fuel cells and metal-air batteries. The design and construct of advanced catalysts can be guided by identifying the sites with high activity. In this study, an indicative research study on the ORR of yam-derived N and S self-doped porous carbons (NSDCs) is presented. The NSDC optimized at 800 degrees C (NSDC800) with more exposed intrinsic N and S active sites shows a comparable ORR activity to the commercial Pt/C and sets the top level for metal-free carbons, as well as high stability and tolerance to CO and methanol. Consequently, a homemade primary Al-air battery with NSDC800 demonstrates an open-circuit potential of 1.66 V and a peak power density of 83 mWcm(-2). With a series of NSDCs, the exposed intrinsic N and S sites (pyrrolic-N, graphitic-N, and thiophene-S) are synergistically identified as the activity indicators for the ORR. This finding may provide an insight into the analysis of active sites and open an avenue for the synthesis and volume production of carbon-based ORR catalysts with low cost and high activity.