Bimetallic nickel-molybdenum/tungsten nanoalloys for high-efficiency overall hydrazine splitting in seawater electrolytes

Replacing sluggish oxygen evolution reaction (OER) by hydrazine oxidation reaction (HzOR) is a promising way to produce hydrogen and suppress unfavorable chlorine evolution reaction (ClER) in long-term seawater splitting. However, few catalysts can meet the demand to process outstanding hydrogen evolution reaction (HER) and HzOR simultaneously to achieve relatively low cell voltage in a two-electrode system. Herein, we report bimetallic Ni 4 Mo/Ni 4 W nanoalloys as bifunctional catalysts with remarkable catalytic activity towards both HER (−7 mV at 10 mA cm −2 ) and HzOR (−16 mV at 10 mA cm −2 ). Surprisingly, low cell voltages of 34, 295 and 548 mV are required to achieve 10, 100 and 200 mA cm −2 in a two-electrode system with ideal stability in 1.0 mol L −1 KOH/2.0 mol L −1 NaCl/0.1 mol L −1 N 2 H 4 electrolyte. Density functional theory calculations disclose that the Ni−Mo/W coupling can not only reduce the free energy of water dissociation as well as hydrogen adsorption/desorption, but also optimize the dehydrogenation kinetics of adsorbed intermediates.