Facile Steam-Etching Approach to Increase the Active Site Density of an Ordered Porous Fe-N-C Catalyst to Boost Oxygen Reduction Reaction

Developing facile and effective strategies to improve theactive site density of transition-metal and nitrogen codoped carbon(M-N-C) catalysts for oxygen reduction reaction (ORR) remains achallenge. Herein, we propose ordered templates and a steam-etchingsynergetic approach to increase the active site density of Fe-N-Ccatalysts with interconnected ordered porous structures. The steametching corrodes inactive amorphous carbon while active sites are wellpreserved. X-ray absorptionfine structure andfitting result reveal theuniform distribution of atomically dispersed Fe-N4active sites. Thesteam etching dramatically increases the active site density by 4.6times, which is verified by the NO adsorption-reduction experiments.As a result, the ORR mass activity of the ordered macroporous Fe-N-C catalyst treated by steam etching at 800 degrees C (OM-Fe-N-C-steam-800) is 1.8 times higher than that of Ar-protected one. The proton-exchange membrane fuel cell employing the OM-Fe-N-C-steam-800 catalyst delivered an enhanced peak power density of 0.78 W cm-2compared to that of Ar-protected counterpart(0.63 W cm-2).