eg Electron Occupancy as a Descriptor for Designing Iron Single‐Atom Electrocatalysts

Abstract A 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 e g electron occupancy from 1.7 to 0.7 are synthesized. A linear relationship has been established between the e g electron occupancy of the Fe site and the catalytic activity/activation entropy of oxygen‐related intermediates. Fe SAC with an e g 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 e g 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 e g electron occupancy descriptor provides valuable insights for designing single‐atom electrocatalysts.