Facile Synthesis of Nickel–Iron/Nanocarbon Hybrids as Advanced Electrocatalysts for Efficient Water Splitting

Developing active, stable, and low-cost electrocatalysts which can promote the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in the same electrolyte is undoubtedly a vital progress toward a hydrogen economy. Herein, we report that such electrocatalysts can be easily prepared by pyrolyzing a precursor composed of nickel and iron salts with urea under inert atmospheres without any post-treatments. The obtained products are composed of metallic nickel–iron alloy nanoparticles either encapsulated in or dispersed on nitrogen-doped bamboo-like carbon nanotubes (CNTs). This simple synthesis route could simultaneously realize nanostructuring, doping, and hybridizing with nanocarbon, which have been demonstrated as efficient strategies to optimize the catalytic activity of an electrocatalyst. The in situ formed hybrid catalysts exhibit good catalytic performances for both OER and HER under alkaline conditions, and the doping content of iron significantly affects the activities. When the best electrocatalyst is loaded on nickel foam with a loading of 2 mg cm–2, a symmetric two-electrode cell can execute overall water splitting at a current density of 10 mA cm–2 with only 1.58 V and shows negligible degradation after 24 h of operation. The excellent electrocatalytic activity and facile preparation method enable this hybrid electrocatalyst to be a promising candidate for future large-scale applications in water splitting.