Ying Guo, Caiping Li, Haibing Meng, Jiawei Wang, Xian-Ming Zhang
The sluggish oxygen reduction reaction (ORR) kinetics significantly hinder the efficiency of fuel cells and metal-air batteries, which have shown great promise for sustainable energy. To address this limitation, much attention has been devoted to the electronic structure modulation of catalysts, but the optimal oxygen-containing moieties supply around active sites is frequently overlooked. In this work, aliphatic thiols were adopted to coordinate with iron phthalocyanine (FePc) to facilitate ORR kinetics. The existing carbon chains enhance the hydrophobic microenvironment around the FeN4 active sites, establishing a robust hydrogen-bond network and optimizing the oxygen-containing moieties supply during the ORR process. Meanwhile, the axial thiols disrupt the original planar symmetric FeN4 structure by enabling FeS coordination, lowering the electron density of Fe sites and preventing the significant spin-state transition upon absorbing the oxygen-containing moieties, which thereby facilitates the rate-determining step of *OH evolution. As a result, FePc coordinated with 1-heptanethiol (FePc-S7) exhibits high ORR activity with a half-wave potential of 0.917 V and an ultralow Tafel slope of 29.12 mV dec-1, surpassing the pristine FePc and many previously reported transition metal-based catalysts. This work highlights the critical roles of synergistic optimization of intermediates supply and electronic structure around the ORR catalytic sites, paving the way for advanced electrocatalysts design and beyond.