Taking Advantage of Potential Coincidence Region: Advanced Self-Activated/Propelled Hydrazine-Assisted Alkaline Seawater Electrolysis and Zn–Hydrazine Battery

Hydrazine-assisted water electrolysis presents a promising energy conversion technology for highly efficient hydrogen production. Owing to the potential coincidence region between hydrogen evolution reaction (HER) and hydrazine electro-oxidation, hydrazine oxidation reaction (HzOR) exhibits specific advantages on strategy combination, device construction, and application expansion. Herein, we report a bifunctional electrocatalyst of porous Ni foam-supported interfacial heterogeneous Ni₂P/Co₂P microspheres (denoted NiCoP/NF), which takes full advantage of this potential coincidence region. Thanks to the 3D microsphere structure and strong interfacial coupling effects between Ni₂P and Co₂P, NiCoP/NF demonstrates excellent bifunctional electrocatalytic performance, requiring ultralow overpotentials of 70 and 230 mV at 10 mA cm^-2 for HER and HzOR, respectively. When using NiCoP/NF as both electrodes, HzOR-assisted water electrolysis exhibits considerably decreased potentials compared with the electro-oxidation of other chemical substrates. Furthermore, the potential coincidence region of 0.1 V makes the application of self-activated/propelled hydrazine-assisted alkaline seawater electrolysis, hydrazine-containing wastewater treatment, and Zn-hydrazine (Zn-Hz) battery realistic. The concept of potential coincidence region provided in this work has significant implications for water electrolysis and other related applications.