Synergistic acid–base interactions enabling stable proton transfer in PEMFCs: insights from simulations and experiments

• Acid–base functionalization provides a cost-effective, reliable, and efficient strategy for PEM fuel cells and electrochemical systems. • Novel acid–base pair strategy integrating AS and Arg into MGC matrix enhances 2D proton conduction pathways and stability. • Comprehensive micro- and spectroscopic analyses revealed structural, chemical, thermal, and electrochemical changes induced by amino-group functionalization. • σ IP and σ TP were measured at low and high temperatures, with conduction mechanisms assessed under dry and hydrated conditions. • Arg-X showed lower PEM performance than AS-X due to its higher pKa, which limited proton release and mobility. • AS-1 membrane possesses an excellent σ IP of 87.04 mS/cm at 90 °C and a MPD of 155.99 mW/cm 2 at 60 °C and 100 % RH. Perfluorosulfonic acid (PFSA)-based membranes such as Nafion® are widely used in proton exchange membrane fuel cells (PEMFCs) but face challenges including fuel crossover, thermal dehydration, poor durability, and high cost. To address this issues, we present a novel acid–base pair nanocomposite membrane strategy by integrating ammonium sulfamate (AS) and L-arginine (Arg) into a covalently modified 3-mercaptopropyltrimethoxysilane–graphene oxide (MPTS–GO) matrix (MGC). Covalent silane modification of GO yielded an acidic framework with –SO 3 H groups, while AS and Arg formed discrete acid–base pairs that enabled efficient two-dimensional proton transport via synergistic Grotthuss and vehicle mechanisms. Molecular dynamics simulations revealed that AS facilitated flexible hydrogen bonding for enhanced conductivity, whereas Arg induced stronger bonding but limited mobility. The interplay between acidic and basic functional groups was systematically correlated with proton conductivity, microstructural evolution, and multidimensional stability encompassing chemical, thermal, and electrochemical aspects. Comprehensive microscopic (FE-SEM, AFM) and spectroscopic (EDS, XPS, PXRD, Raman, UV–Vis, FTIR) analyses, along with electrochemical impedance spectroscopy (EIS), confirmed the development of structurally robust frameworks with continuous proton-conduction networks. Proton conduction is explicitly governed by synergistic Grotthuss hopping along hydrogen-bond networks and vehicle-mediated diffusion, with AS-X membranes favoring dual-mode transport and Arg-X membranes exhibiting predominantly vehicle-mediated diffusion. Optimized AS-1 and Arg-0.5 membranes achieve in-plane proton conductivities of 87.04 and 68.27 mS/cm at 90 °C, with reduced activation energies and long-term stability under both humid and anhydrous conditions. AS-1 delivered a peak power density of 155.99 mW/cm 2 at 60 °C, surpassing pristine MGC through improved proton transport through synergistic acid–base interactions, suppressed fuel crossover, and maintaining chemical/oxidative integrity. In Fenton’s test, AS-1 and Arg-0.5 retained >95 % mass after 12 h and remained stable up to 1000 h, while pristine MGC degraded completely within 100 h. In contrast, Arg-X showed lower PEM performance due to its higher pKa, which hindered H + dissociation and reduced proton mobility. This work establishes a scalable, cost-effective approach for high-performance PEMs and highlights the practical potential of acid–base pair engineering for next-generation PEMFCs and related electrochemical devices.