<i>e</i>_g Electron Occupancy as a Descriptor for Designing Iron Single‐Atom Electrocatalysts

Abstract

AbstractA quantitative electronic structure‐performance relationship is highly desired for the design of single‐atom catalysts (SACs). The Fe single‐atom catalysts supported by ordered mesoporous carbon with the eg electron occupancy from 1.7 to 0.7 are synthesized. A linear relationship has been established between the eg electron occupancy of the Fe site and the catalytic activity/activation entropy of oxygen‐related intermediates. Fe SAC with an eg electron occupancy of 0.7 alters the rate determining step from *OH desorption to *OOH formation. The value of the turn‐over frequency is ≈28 times that of the Fe SAC site with an eg electron occupancy of 1.7 e, and the mass activity is ≈6.3 times that of commercial Pt/C. When used in a zinc–air battery, the Fe SAC gives a remarkable power density of 196.3 mW cm−2 and a long‐term stability exceeding 1500 h. The discovery of eg electron occupancy descriptor provides valuable insights for designing single‐atom electrocatalysts.