Molecular Cation Trap Engineering via H‐Bond and π‐d Synergy in a ZnCo‐ZIF/N‐MXene Heterostructure for Ultrafast Ammonium‐Ion Storage

ABSTRACT

Ammonium ions (NH ₄ ⁺ ) offer a dual mechanism for electrochemical storage, combining tetrahedral geometry for hydrogen bonding with a non‐polar π‐face primed for cation–π interactions. However, no single electrode material has successfully harnessed both pathways synergistically. Herein, ZnCo‐ZIF/N‐MXene heterostructure engineered as a molecular cation trap deliberately integrating complementary chemisorption sites. The conductive N‐MXene scaffold provides abundant hydrogen‐bonding acceptors, while the anchored ZIF nanoparticles, electronically modulated by interfacial charge transfer, activate robust cation–π interactions via π–d orbital hybridization at Co centers. This dual‐reaction‐center mechanism enables unparalleled NH ₄ ⁺ storage, delivering an ultrahigh specific capacitance of 1380.6 F g ⁻¹ at 1 A g ⁻¹ with 94.3% capacitance retention over 10 000 cycles. A suite of in/ex situ spectroscopic and electrochemical probes, including XAFS and in situ EIS, provides direct evidence for the charge transfer that enables cation–π bonding and the highly reversible kinetics afforded by cooperative hydrogen bonding. Constructed as a full‐cell NH ₄ ⁺ ‐HSC (ZIF/N‐MXene//ZIF‐rGO), the device achieves a top‐tier energy density of 98.2 Wh kg ⁻¹ at 1000 W kg ⁻¹ , with 88.3% capacity retention over 10 000 cycles—significantly outperforming state‐of‐the‐art systems. This work establishes a definitive interface‐engineering strategy for harnessing molecular‐ion duality, paving the way for next‐generation energy storage systems.