Self-Limited Formation of Cobalt Nanoparticles for Spontaneous Hydrogen Production through Hydrazine Electrooxidation.

Hydrogen (H 2 ) has emerged as a highly promising energy carrier owing to its remarkable energy density and carbon emission-free properties. However, the widespread application of H 2 fuel has been limited by the difficulty of storage. In this work, spontaneous electrochemical hydrogen production is demonstrated using hydrazine (N 2 H 4 ) as a liquid hydrogen storage medium and enabled by a highly active Co catalyst for hydrazine electrooxidation reaction (HzOR). The HzOR electrocatalyst is developed by a self-limited growth of Co nanoparticles from a Co-based zeolitic imidazolate framework (ZIF), exhibiting abundant defective surface atoms as active sites for HzOR. Notably, these self-limited Co nanoparticles exhibit remarkable HzOR activity with a negative working potential of -0.1 V (at 10 mA cm -2 ) in 0.1 m N 2 H 4 /1 m KOH electrolyte. Density functional theory (DFT) calculations are employed to validate the superior performance of low-coordinated Co active sites in facilitating HzOR. By taking advantage of the potential difference between HzOR and the hydrogen evolution reaction (HER), a novel HzOR||HER electrochemical system is developed to spontaneously produce H 2 without external energy input. Overall, the work offers valuable guidance for developing active HzOR catalyst. The novel HzOR||HER electrochemical system represents a promising and innovative solution for energy-efficient hydrogen production.