Bifunctional Fe─Ru─VC Catalyst for Energy Efficient Tandem Alkaline Electrolysis of Hydrazine and 4-nitrophenol

Alternate electrocatalytic reactions can turn pollutants into green fuels, offering an energy-efficient approach. Coupling hydrazine oxidation reaction (HzOR), with 4-nitrophenol hydrogenation (4-NPHR) is especially promising. Here, we report a bifunctional electrocatalyst composed of defect-rich Fe–Ru alloy clusters uniformly anchored on vanadium carbide (Fe─Ru─VC), synthesized via scalable ball milling and thermal annealing. Fe─Ru─VC exhibits excellent electrocatalytic activity toward both HzOR and 4-NPHR, requiring a low overpotential of 145 mV at 10 mA cm⁻² and a favorable Tafel slope of 68.9 mV dec⁻¹ for HzOR, with stability exceeding 90 h in 1M KOH. For 1 mM 4-NPHR, superior Fe-Ru-VC performance is achieved −7.2 mA cm⁻² at 100 mV, highlighting its high efficiency. Furthermore, a paired H-cell electrolyzer (HzOR||4-NPHR) operates at only 200 mV to deliver 40 mA cm⁻², underscoring its low energy demand. In situ Raman spectroscopy confirms the formation of Fe─Ru(OOH) as active sites, UV–Vis analysis confirms rapid 4-NP degradation, and DFT calculations demonstrate enhanced electronic interactions at the Ru─Fe junction, consistent with experimental observations. The outstanding activity is attributed to synergistic Fe-Ru interactions, the presence of zigzag edge defects, and the excellent conductivity of the VC support.