Encapsulation of Ni nanoparticles in O-doped carbon as chainmail electrocatalyst for alkaline seawater hydrogen evolution

<p>Carbon encapsulation represents a promising strategy for enhancing the activity and stability of the nanocatalysts <i>via</i> the chainmail approach, showing great potential in seawater electrolysis. Herein, a chainmail design is proposed to synthesize nickel nanoparticles protected with an O-doped graphitic shell on carbon nanotubes (Ni@O-C/CNTs) for highly efficient and stable hydrogen evolution reaction (HER) in alkaline seawater. Ni@O-C/CNTs are synthesized by <i>in situ</i> pyrolysis of salicylate intercalated layered nickel hydroxides, forming abundant Ni-O-C bonds at the interface. This chainmail design facilitates the penetration of valence electrons from the active Ni core to the graphitic shell, thereby promoting the adsorption of intermediates involved in HER. Moreover, the enriched O groups on CNTs enhance hydrophilicity and aerophobicity, facilitating electrolyte transport and hydrogen evolution during HER. Owing to the unique chainmail design, Ni@O-C/CNTs exhibit excellent HER performance in real alkaline seawater with a 58 mV overpotential at the current density of 10 mA cm<sup>−2</sup> and maintain stability at a current density of 150 mA cm<sup>−2</sup> over 2000 hours. Impressively, a high energy efficiency of 80% and stability of up to 300 hours are achieved for the alkaline seawater electrolyzer assembled using Ni@O-C/CNTs under practical conditions.</p>