MRI-Visualized Aqueous Microenvironment Engineering in 3D Hierarchical FePt Catalysts with Macroporous Architecture for Alkaline Hydrogen Evolution

Electrolytic water splitting is a promising strategy for sustainable hydrogen production, yet the alkaline hydrogen evolution reaction (HER) faces kinetic bottlenecks: high water dissociation energy and weak water adsorption. Herein, we first designed a model micrometer-scale 3D hierarchical FePt catalyst (FePt@3D) system with architecturally tailored supports to amplify interfacial water-catalyst interactions while matching the spatial resolution of magnetic resonance imaging (MRI). Spatiotemporally resolved <i>T</i>₂-weighted imaging (<i>T</i>₂-WI) revealed that FePt@MP-3D performed water enrichment by 28% through capillary forces and increased tortuosity, corresponding to a low overpotential of 13.8 mV at 10 mA cm^-2, surpassing commercial Pt/C (η₁₀ = 14.4 mV). This work establishes MRI as a transformative tool to map spatiotemporal distribution of water molecules at catalytic interfaces, bridging macroscopic water distribution with nanoscale catalytic activity. It is clearly shown that MRI provides a powerful tool for probing the other electrocatalytic reactions (e.g., CO₂RR, ORR), where water/ion transfer governs performance.