Silk-Derived 2D Porous Carbon Nanosheets with Atomically-Dispersed Fe-N x -C Sites for Highly Efficient Oxygen Reaction Catalysts.

Controlled synthesis of highly efficient, stable, and cost-effective oxygen reaction electrocatalysts with atomically-dispersed Me-N-x-C active sites through an effective strategy is highly desired for high-performance energy devices. Herein, based on regenerated silk fibroin dissolved in ferric chloride and zinc chloride aqueous solution, 2D porous carbon nanosheets with atomically-dispersed Fe-N-x-C active sites and very large specific surface area (approximate to 2105 m(2) g(-1)) are prepared through a simple thermal treatment process. Owing to the 2D porous structure with large surface area and atomic dispersion of Fe-N-x-C active sites, the as-prepared silk-derived carbon nanosheets show superior electrochemical activity toward the oxygen reduction reaction with a half-wave potential (E-1/2) of 0.853 V, remarkable stability with only 11 mV loss in E-1/2 after 30 000 cycles, as well as good catalytic activity toward the oxygen evolution reaction. This work provides a practical and effective approach for the synthesis of high-performance oxygen reaction catalysts towards advanced energy materials.