Regulating Ru active sites by Pd alloying to significantly enhance hydrazine oxidation for energy-saving hydrogen production

Abstract

Integrating the hydrogen evolution reaction (HER) with the hydrazine oxidation reaction (HzOR) can construct a novel electrolytic system and thus accomplish energy-efficient H₂ production, which necessitates exploring excellent bifunctional electrocatalysts for the HER and HzOR. As alternatives to prohibitive and scarce Pt, alloy materials can synergistically exhibit appreciably enhanced catalytic activity, and simultaneously can be also endowed with a bifunctionality arising from the intermixed components. Herein, we facilely synthesized ultrafine RuPd alloy nanoparticles onto pretreated activated carbon (RuPd/C), which possesses improved dispersion and tailored electronic properties relative to mono-metallic samples, thus exhibiting remarkably boosted bifunctional performance for alkaline HER and HzOR. At 10 mA cm⁻², RuPd/C merely demands ultralow potentials of −15.3 mV for the HER and −77.9 mV for the HzOR, overmatching Pt/C. Moreover, the two-electrode cell just requires a voltage of 17.7 and 147.6 mV to afford 10 and 100 mA cm⁻², much superior to traditional water splitting (∼2 V), displaying its immense superiority in energy saving, which can be also readily driven by a self-made direct hydrazine fuel cell and commercial solar cell with an appreciable H₂ generation of 0.85 and 0.98 mmol h⁻¹, respectively. Theoretical calculations unravel that the HER and HzOR both occur on Ru sites, which can be achieved by Pd alloying with a lower water dissociation barrier and optimized hydrogen adsorption free energy for the HER, and also improved dehydrogenation kinetics for the HzOR.