A new non-platinum PEMFC catalyst approach centers on an inner curved-surface single-atom iron site housed within nanoconfined hollow multishelled (HoMS) structures dispersed on 2D carbon, with Fe concentrated on the inner layers.

This design signals a potential new paradigm for high-performance, durable non-platinum PEMFC catalysts and could accelerate next-generation electrocatalysts.

Theoretical work shows a nitrogen-doped outer shell with Fe vacancies creates electrostatic repulsion that weakens adsorption of intermediates, breaking scaling relations and boosting activity.

Performance highlights include an oxygen reduction overpotential of about 0.34 V, reduced hydrogen peroxide formation, high selectivity and durability, and a record power density of 0.75 W/cm² at 1 bar H2–air with 86% activity retained after more than 300 hours.

Earlier work from a Chinese team introduced an iron-based CS Fe/N-C catalyst for proton exchange membrane fuel cells to cut platinum usage.

An outer graphitized carbon layer provides protection and weakens binding of oxygen intermediates, creating an inner-activation, outer-protection microenvironment that enhances stability.

X-ray spectroscopy and Mössbauer measurements show Fe predominantly in the +2 state with FeN4C10 coordination, and about 57.9% of Fe sites in an active low-spin D1 state.