1D/3D Heterogeneous Assembling Body of Cobalt Nitrides for Highly Efficient Overall Hydrazine Splitting and Supercapacitors.

Herein, the construction of a heterostructured 1D/3D CoN-Co 2 N@NF (nickel foam) electrode used for thermodynamically favorable hydrazine oxidation reaction (HzOR), as an alternative to sluggish anodic oxygen evolution reaction (OER) in water splitting for hydrogen production, is reported. The electrode exhibits remarkable catalytic activities, with an onset potential of -0.11 V in HzOR and -71 mV for a current density of 10 mA cm -2 in hydrogen evolution reaction (HER). Consequently, an extraordinary low cell voltage of 53 mV is required to achieve 10 mA cm -2 for overall hydrazine splitting in a two-electrode system, demonstrating significant energy-saving advantages over conventional water splitting. The HzOR proceeds through the 4e - reaction pathway to release N 2 while the 1e - pathway to emit NH 3 is uncompetitive, as evidenced by differential electrochemical mass spectrometric measurements. The X-ray absorption spectroscopy, in situ Raman spectroscopy, and theoretical calculations identify cobalt nitrides rather than corresponding oxides/(oxy)hydroxides as catalytic species for HzOR and illustrate advantages of heterostructured CoN-Co 2 N in optimizing adsorption energies of intermediates/reagents and promoting catalytic activities toward both HzOR and HER. The CoN-Co 2 N@NF is also an excellent supercapacitive material, exhibiting an increased specific capacity (938 F g -1 at 1 A g -1 ) with excellent cycling stability (95.8%, 5000 cycles).