Structural innovations in oxygen reduction electrocatalysts for proton exchange membrane fuel cells

Proton exchange membrane fuel cells (PEMFCs) are promising clean energy technologies for automotive and stationary applications due to their high efficiency and low emissions. However, their large-scale commercialization is hindered by the sluggish kinetics of the oxygen reduction reaction (ORR), which demands high loadings of scarce platinum (Pt). Addressing this challenge requires a paradigm shift from conventional compositional optimization toward multi-scale structural innovation. This review systematically summarizes recent advances in the rational design of ORR electrocatalysts through three interconnected aspects: engineering metal nanostructures (noble/non-noble systems) to enhance active-site exposure and tune electronic properties; developing advanced catalyst supports (carbon/non-carbon substrates) to improve metal dispersion and synergistic interactions; and tailoring metal–support interfaces to regulate charge transfer and intermediate adsorption. Particularly, structural control across these dimensions governs key processes, including mass transport, electron transfer, and reaction pathways, thereby enhancing intrinsic activity and stability. Finally, current challenges and future opportunities are discussed for translating these advances into practical fuel cell systems, emphasizing the critical role of integrated structural design in enabling next-generation electrocatalysts.