g‐C3N4‐Mediated Synthesis of Ru Crystalline/Amorphous Heterostructures on N‐Doped Carbon for Efficient and Chloride‐Resistant Alkaline HER

Abstract Developing Pt‐alternative electrocatalysts for the hydrogen evolution reaction (HER) requires balancing activity, stability, and corrosion resistance. Herein, a g‐C 3 N 4 ‐mediated pyrolysis strategy is reported to construct nitrogen‐doped carbon‐anchored Ru nanoparticles with a crystalline/amorphous heterostructure (a/c‐Ru@NC). During pyrolysis, g‐C 3 N 4 coordinates Ru 3+ ions via N‐sites and releases reductive gases for in situ reduction. Strong Ru─N bonding disrupts the atomic ordering in the core, forming amorphous Ru (a‐Ru). Under the reductive atmosphere, the outer region further crystallizes into the crystalline phase (c‐Ru) while the amorphous core remains preserved, thereby creating a phase‐junction structure. The resulting catalyst exhibits ultrahigh dispersion (≈2.27 nm particles, 1 wt.% Ru loading) with optimized electronic properties. In 1.0 m KOH, a/c‐Ru@NC achieves a low overpotential of 15 mV at 10 mA cm −2 , a highly competitive mass activity of 24.312 A mg Ru −1 (37 × higher than Pt/C), and negligible decay after 250 h operation. Crucially, it demonstrates exceptional chloride‐corrosion resistance, showing only 8 mV overpotential increase from 0 m to saturated NaCl in electrolyte, much lower than that of commercial Ru/C (44 mV) and Pt/C (23 mV). This work provides a heterostructure design paradigm for sustainable hydrogen production in saline environments.