Work

Hydrogen-bond-mediated ion transport and reaction-field dynamics in porous Co₉S₈/CNT cathodes for ammonium storage

Year: 2026

Type: article

Abstract: Aqueous ammonium-ion batteries offer a promising platform for safe and sustainable electrochemical energy storage, yet the coupled physicochemical mechanisms governing NH₄⁺ transport, interfacial interactions, and spatial charge-storage behavior remain insufficiently understood. This study presents a physics-based framework for elucidating the role of reversible hydrogen-bond interactions in regulating NH₄⁺ transport, interfacial charge-transfer kinetics, and reaction-field redistribution within porous Co₉S₈/CNT cathodes. The framework couples non-ideal ionic transport, electronic charge conservation, Butler–Volmer kinetics, reversible hydrogen-bond formation and rupture, double-layer charging, phase evolution, and state-dependent porous-electrode properties. The results reveal a nonmonotonic relationship between hydrogen-bond occupation and electrochemical utilization. Moderate and reversible hydrogen bonding redistributes the Faradaic reaction field and increases participation of internal reaction domains, increasing the Reaction Uniformity Index from 0.74 to 0.87 while raising the Microsphere Depth Utilization Factor from 0.47 to 0.58. In contrast, excessive bond occupation reduces the mobile-ion population, intensifies concentration polarization, and promotes localization of electrochemical activity near the outer particle region. CNT connectivity further modulates the coupled transport–reaction behavior by homogenizing electronic conduction and enhancing the accessibility of internal reaction zones, reducing the electrolyte potential drop from 47.0 to 11.9 mV across the investigated connectivity range. Sensitivity and uncertainty analyses identify hydrogen-bond kinetics, ionic transport, accessible bonding-site density, and structural connectivity as strongly coupled governing factors. These findings demonstrate that hydrogen bonding functions as a dynamic kinetic regulator rather than a passive adsorption interaction and provide a mechanistic basis for balancing reversible molecular-ion association, ionic mobility, and spatially distributed electrochemical activity in porous electrode architectures.

Source: Chemical Physics Impact

DOI: 10.1016/j.chphi.2026.101156