Sulfur‐Mediated Microenvironment Modulation of High‐Density Fe‐N <sub>4</sub> Sites for High‐Efficiency Oxygen Reduction and Cryotolerant Quasi‐Solid‐State Zinc‐Air Batteries
Chen Zhao, Bingxian Chu, Hao Nian, Bing Shao, Yu Lu, Fanchao Zhang, Yang‐Gang Wang, Qiang Xü
Abstract
Abstract Single‐atom catalysts (SACs) featuring Fe‐N 4 active sites hold significant potential for the oxygen reduction reaction (ORR). However, achieving high‐density Fe‐N 4 active sites while precisely modulating their microenvironment to enhance ORR activity remains a formidable challenge. Here, an S‐mediated strategy is presented for the preparation of Fe single‐atom‐loaded S,N‐doped carbon (FeNSC). This strategy leverages the interactions between S and N during pyrolysis to significantly suppress N loss, thereby achieving a high density of Fe‐N 4 sites. Concurrently, the precise doping of S into the second coordination shell of Fe‐N 4 centers modulates their electronic structure, leading to a significant weakening of * O and * OH intermediates adsorption during the ORR. Consequently, the FeNSC catalyst exhibits excellent pH‐universal ORR performance with half‐wave potentials of 0.928 V (0.1 M KOH), 0.806 V (0.1 M HClO 4 ), and 0.755 V (0.1 M phosphate buffer solution). A FeNSC‐based quasi‐solid‐state zinc‐air battery (QSS‐ZAB) achieves smooth operation over a broad temperature range of −40 to 60 °C. Notably, it sustains continuous operation for over 940 h at −40 °C, showcasing unprecedented cryotolerance. This work provides novel insights into the electronic microenvironment engineering of Fe‐N 4 sites in SACs for high‐efficiency ORR and cryotolerant QSS‐ZABs.