Hierarchical‐Pore‐Stabilization Strategy for Fabricating 18.3 wt% High‐Loading Single‐Atom Catalyst for Oxygen Reduction Reaction

Abstract Metal single‐atom catalysts (M‐SACs) attract extraordinary attention for promoting oxygen reduction reaction (ORR) with 100% atomic utilization. However, low metal loading (usually less than 2 wt%) limits their overall catalytic performance. Herein, a hierarchical‐structure‐stabilization strategy for fabricating high‐loading (18.3%) M‐SACs with efficient ORR activity is reported. Hierarchical pores structure generated with high N content by SiO₂ can provide more coordination sites and facilitate the adsorption of Fe³⁺ through mesoporous and confinement effect of it stabilizes Fe atoms in micropores on it during pyrolysis. High N content on hierarchical pores structure could provide more anchor sites of Fe atoms during the subsequent secondary pyrolysis and synthesize the dense and accessible Fe‐N₄ sites after subsequent pyrolysis. In addition, Se power is introduced to modulate the electronic structure of Fe‐N₄ sites and further decrease the energy barrier of the ORR rate‐determining step. As a result, the Fe single atom catalyst delivers unprecedentedly high ORR activity with a half‐wave potential of 0.895 V in 0.1 M KOH aqueous solution and 0.791 V in 0.1 M HClO₄ aqueous solution. Therefore, a hierarchical‐pore‐stabilization strategy for boosting the density and accessibility of Fe‐N₄ species paves a new avenue toward high‐loading M‐SACs for various applications such as thermocatalysis and photocatalysis.