Silver Oxide Nanoparticles as Solid-State Hydroxide Ion Conductors for Watt-Scale Anion Exchange Membrane Fuel Cells

Inorganic solid-state hydroxide ion conductors have emerged as stable platforms for high-temperature alkaline energy conversion technologies. Although several materials have shown promising ionic conductivity in model studies, their direct implementation in operating devices has remained largely unexplored. Here, we demonstrate that silver-(I) oxide (Ag₂O) nanoparticles can function as hydroxide ion conductors within anion exchange membrane fuel cells (AEMFCs). Syringe-filtered 1-6 nm Ag₂O nanoparticles were integrated into Pt/C cathodes, establishing ionic conduction pathways across the cathode-membrane interface. The resulting ionomer-free membrane electrode assembly (MEA) achieved 1.91 W cm^-2 peak power density at 2.4 wt % Ag₂O loading and maintained stable mass transport during 100 h of continuous operation at 0.6 A cm^-2. Electrochemical and structural analyses revealed how Ag₂O loading influences ionic conduction, pore structure, and mass transport behavior in ways that are partially distinct from conventional ionomer-based electrodes. These findings highlight inorganic solid-state conductors as promising design analogues to ionomers for high-performance, ionomer-free AEMFC cathodes.