Lignin-Directed Construction of Vertical Ru/RuO 2 Electron–Bridge Interfaces for Low-Input Self-Powered Hydrazine-Water Splitting

Hydrazine oxidation reaction (HzOR) has emerged as a promising anodic alternative to the oxygen evolution reaction (OER) for efficient hydrogen production. Nevertheless, two-electrode electrolyzers demand substantial cell voltages and uninterrupted external power, curbing scalable implementation. Herein, hydrothermally activated lignin chelates with Ru³⁺ to direct the in situ formation of Ru/RuO₂ heterojunctions that, upon pyrolysis, are embedded within a hierarchical lignin-derived carbon (HLC) matrix to yield the Ru/RuO₂@HLC catalyst. Combined spectroscopy and DFT calculation uncover a dynamic dual-center (DDC) at the interface: a Ru⁴⁺-O-Ru⁰ electron bridge injects charge into RuO₂, while adjacent Ru undergoes reversible partial oxidation (Ru⁰ ↔ Ru³⁺) under bias. This DDC slightly elongates Ru-O and compresses Ru-Ru, enriches lattice oxygen, accelerates interfacial charge transfer, lowers the free-energy barrier of the rate-limiting *2NH → *2N step to 1.31 eV, and suppresses high-valence Ru dissolution. In 1.0 M KOH electrolyte, the as-prepared Ru/RuO₂@HLC catalyst achieves a hydrogen evolution reaction (HER) current density of 50 mA cm^-2 at an exceptionally low overpotential of 12 mV and surpasses commercial Pt/C. Replacing OER with HzOR significantly reduces the cell voltage to only 0.14 V at 100 mA cm^-2. A paired direct hydrazine fuel cell and an integrated overall hydrazine splitting deliver 2.32 mmol h^-1 of hydrogen at approximately 100% Faradaic efficiency, representing one of the highest hydrogen production rates reported to date for self-powered hydrazine systems. This work provides a scalable platform for waste-to-hydrogen conversion and highlights the potential of renewable biomass ligands for constructing high-performance interfacial electrocatalysts.