Reconstruction of Ultrafine MnS‐Induced Vacancy‐Rich Co 9 S 6.29 Precatalysts in Mesoporous S‐Doped N‐Rich Hollow Carbon Nanotubes Enables Dynamic O
Debarani Devi Khumujam, Saleem Sidra, Ram Babu Ghising, Dong Won Kim, Jong Hui Choi, Gwanho Lee, Benzhi Wang, Hyung Mo Jeong, Sang‐Il Choi, Do Hwan Kim, Jeung Ku KangABSTRACT
Zn‐air batteries (ZABs) hold great promise when the air cathode offers abundant active sites, fast kinetics, and high reversibility for oxygen reduction/evolution reactions (ORR/OER). Here, we report vacancy‐rich Co 9 S 6 . 29 precatalysts formed via ultrafine MnS‐induced lattice distortion in mesoporous S‐doped pyridinic/graphitic N‐rich hollow carbon nanotubes (CM@SNHCTs), synthesized through in situ sulfidation and Zn/melamine evaporation from polydopamine‐coated Mn–Co/Zn metal–organic frameworks. MnS‐induced Co 9 S 6 . 29 formation enables ∼fourfold higher capacitance than IrO 2 , while the SNHCT generates Zn/melamine‐evaporated mesoporous S‐doped pyridinic N‐rich channels for rapid ion transport and graphitic N‐rich networks for facile electron conduction. CM@SNHCT precatalysts reconstruct into CoOOH/CoO active phases, enabling O‐vacancy formation via OH − desorption during ORR and bidentate O 2 adsorption during OER, as well as O‐vacancy healing governed by OH − adsorption and deprotonation, as confirmed by operando Raman spectroscopy and 1 8 O‐labeled differential electrochemical mass spectrometry. Density functional theory calculations reveal low Gibbs free‐energy barriers for oxygen intermediates after reconstruction, while strong CM‐SNHCT binding ensure structural stability. Consequently, CM@SNHCT outperforms Pt/C for ORR and IrO 2 for OER with electrochemical stability over 5000 cycles. Moreover, the ZAB assembled with CM@SNHCT cathode and high‐capacity Zn anode achieves near‐theoretical energy density (993.8 Wh·kg − 1 ) and stable voltages after 250 charge–discharge cycles, establishing a state‐of‐the‐art ZAB platform.