Facet Engineering and Pore Design Boost Dynamic Fe Exchange in Oxygen Evolution Catalysis to Break the Activity-Stability Trade-Off

The oxygen evolution reaction (OER) plays a vital rolein renewableenergy technologies, including in fuel cells, metal-air batteries,and water splitting; however, the currently available catalysts stillsuffer from unsatisfactory performance due to the sluggish OER kinetics.Herein, we developed a new catalyst with high efficiency in whichthe dynamic exchange mechanism of active Fe sites in the OER was regulatedby crystal plane engineering and pore structure design. High-densitynanoholes were created on cobalt hydroxide as the catalyst host, andthen Fe species were filled inside the nanoholes. During the OER,the dynamic Fe was selectively and strongly adsorbed by the (101 0)sites on the nanohole walls rather than the (0001) basal plane, andat the same time the space-confining effect of the nanohole sloweddown the Fe diffusion from catalyst to electrolyte. As a result, alocal high-flux Fe dynamic equilibrium inside the nanoholes for OERwas achieved, as demonstrated by the Fe-57 isotope labeledmass spectrometry, thereby delivering a high OER activity. The catalystshowed a remarkably low overpotential of 228 mV at a current densityof 10 mA cm(-2), which is among the best cobalt-basedcatalysts reported so far. This special protection strategy for Fealso greatly improved the catalytic stability, reducing the Fe leachingamount by 2 orders of magnitude compared with the pure Fe hydroxidecatalyst and thus delivering a long-term stability of 130 h. An assembledZn-air battery was stably cycled for 170 h with a low discharge/chargevoltage difference of 0.72 V.