A Freestanding Single‐Wall Carbon Nanotube Film Decorated with N‐Doped Carbon‐Encapsulated Ni Nanoparticles as a Bifunctional Electrocatalyst for Overall Water Splitting

Abstract

Noble-metal free, cost-effective, and highly stable catalysts with efficient activity for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) have attracted tremendous research interest in recent years. Here, a flexible, self-standing hybrid film comprising a N-doped single-wall carbon nanotube (SWCNT) network on which are anchored Ni nanoparticles encapsulated by a monolayer of N-doped carbon (NCNi) is reported. The films are prepared by floating catalyst chemical vapor deposition followed by NH₃ treatment. The material obtained at optimum conditions shows excellent bifunctional electrocatalytic activity in alkaline media with low overpotentials of 190 and 270 mV for HER and OER, respectively, to reach a current density of 10 mA cm^-2. A current density of 10 mA cm^-2 at 1.57 V is achieved when this freestanding and binder-free rod-shaped NCNi/SWCNT assembly is used as cathode and anode in 1 m KOH solution for overall water splitting, presenting one of the best values reported to date.