Highly enhanced hydrazine oxidation on bifunctional Ni tailored by alloying for energy-efficient hydrogen production

The low-potential hydrazine oxidation reaction (HzOR) can replace the oxygen evolution reaction (OER) and thus assemble with the hydrogen evolution reaction (HER), consequently achieving energy-saving hydrogen (H₂) production. Notably, developing sophisticated bifunctional electrocatalysts for HER and HzOR is a prerequisite for efficient H₂ production. Alloying noble metals with eligible non-precious ones can increase affordability, catalytic activity, and stability, alongside rendering bifunctionality. Herein, RuNi alloy deposited onto carbon (RuNi/C) was directly prepared by a simple and highly practical co-reduction method, showing excellent performance for HER and HzOR. Interestingly, to achieve 10 mA cm^-2, RuNi/C only required an ultralow potential of 24 mV for HER, on par with commercial 20 wt% platinum in carbon (Pt/C), and -65 mV for HzOR, surpassing most reported counterparts. Moreover, the two-electrode electrolyzer only required small operation voltages of 57.8 and 327 mV to drive 10 and 100 mA cm^-2, respectively. Driven by a homemade hydrazine (N₂H₄) fuel cell and solar panel, appreciable H₂ yields of 1.027 and 1.406 mmol h^-1 were achieved, respectively, exhibiting the energy-saving advantages alongside robust practicability. Moreover, theoretical calculations revealed that alloying with Ru endows bifunctional Ni sites not only with a lower H₂O dissociation barrier but also with more favorable H* adsorption alongside the reduced energy barrier between HzOR intermediates.