biostudies-literatureUnknownTao JAtomically dispersed transition metal, nitrogen co-doped carbon (M-N-C) is hailed as the most promising platinum alternative for the oxygen reduction reaction (ORR); however, its practical deployment is bottlenecked by inferior intrinsic activity and insufficient site density. Herein, we report a sodium borohydride (NaBH₄) assisted synthesis strategy to achieve dual enhancement of active site density and intrinsic activity. This strategy endows a B-doped catalyst (denoted as Fe-sZ8-N-C) with a high active site density of 2.26 × 10²⁰ sites per g, a two-fold enhancement over conventional Fe-N-C. Besides, the intrinsic activity of the catalyst is improved from 0.96 e per site per s to 1.5 e per site per s. Density functional theory (DFT) calculations reveal that the boroChemical sciencehttps://www.ebi.ac.uk/biostudies/studies/S-EPMC12426768biostudies-literatureDual-function synergy in boron-doped Fe-N-C: enhanced site density and intrinsic activity.PMC12426768Yang XLiu XTao JXiao MLi CXing WGuan XShao MBai JLiu CfalseDual-function synergy in boron-doped Fe-N-C: enhanced site density and intrinsic activity.Atomically dispersed transition metal, nitrogen co-doped carbon (M-N-C) is hailed as the most promising platinum alternative for the oxygen reduction reaction (ORR); however, its practical deployment is bottlenecked by inferior intrinsic activity and insufficient site density. Herein, we report a sodium borohydride (NaBH₄) assisted synthesis strategy to achieve dual enhancement of active site density and intrinsic activity. This strategy endows a B-doped catalyst (denoted as Fe-sZ8-N-C) with a high active site density of 2.26 × 10²⁰ sites per g, a two-fold enhancement over conventional Fe-N-C. Besides, the intrinsic activity of the catalyst is improved from 0.96 e per site per s to 1.5 e per site per s. Density functional theory (DFT) calculations reveal that the boro2025-01-01T00:00:00Z2025 Sep2026-06-02T10:04:34.575Z2026-05-26T03:06:42.527ZS-EPMC124267684095178510.1039/d5sc05135e