Hydrogen bond cooperative effects and proton transfer barriers in water clusters: Implications for proton-conductive energy materials

Abstract

In the context of new energy materials and hydrogen-based energy systems, understanding proton transfer (PT) mechanisms is critical for optimizing proton exchange membranes and hydrogen storage materials. This study investigates hydrogen bond (H-bond) cooperative energies and concerted intralayer proton transfer (CIntraPT) barriers in cyclic and prismatic water clusters as model systems. We find that the average H-bond interaction energies (7.81 – 9.98 kcal · mol −1) are strongly modulated by both the structural dimensionality and cooperative effects, with electrostatic charge variations (0.01-0.09e) during proton delocalization enhancing charge redistribution. Notably, the CIntraPT barriers (11-15 kcal·mol−1 after ZPE correction) increase with the number of transferring protons, which contradicts the trend of H-bond strength, indicating that H-bond energy alone is insufficient to determine PT kinetics. Instead, nuclear vibrations–particularly symmetric stretching modes (435-562 cm−1) – are identified as key facilitators that synchronize proton motions along H-bond networks, effectively reducing kinetic barriers. These findings provide fundamental insights into proton dynamics in confined hydrogen-bonded systems, offering theoretical guidance for designing high-performance proton-conductive materials for fuel cells, electrolyzers, and other energy conversion devices.