Quantum-sized CoP nanodots with rich vacancies: Enhanced hydrazine oxidation, hydrazine-assisted water splitting, and Zn-hydrazine battery performance through interface modulation.

Reducing the size of catalysts and tuning their electronic structure and interfacial properties are key to enhancing catalytic performance. Herein, a series of quantum-sized Co-based nanodot composites, including Co₃O₄/C, CoS₂/C, CoN/C, and CoP/C, were synthesized using chemical vapor deposition (CVD) methods. By means of experimental measurement and theoretical calculation, CoP/C exhibited more robust electrochemical response than other Co-based compounds in electrochemical oxidation of N₂H₄ (HzOR) and hydrogen evolution reaction (HER). The catalytic activities of CoP/C can be further enhanced by introducing Co vacancies on the surface of CoP/C (labeled as Co_1-xP/C). The results demonstrated that Co_1-xP/C not only exhibited notable electrochemical responses at an ultra-low N₂H₄ concentration of 0.67 μM, showcasing its potential for ultra-sensitive N₂H₄ detection but also realized HzOR instead of the oxygen evolution reaction (OER) half-reaction, thereby lowering the overpotential to 2.0 mV at 10.0 mA cm^-2. Finally, a Zn-hydrazine (Zn-Hz) battery was fabricated as a promising energy conversion device, showing the exceptional practical value of Co_1-xP/C.