A Flexible Electrode Based on Al-Doped Nickel Hydroxide Wrapped around a Carbon Nanotube Forest for Efficient Oxygen Evolution

The development of highly active, cheap, and stable electrocatalysts for overall water splitting is strategic for industrial electrolysis processes aiming to achieve sustainable hydrogen production. Here, we report the impressive electrocatalytic activity of the oxygen evolution reaction of Al-doped Ni(OH)2 deposited on a chemically etched carbon nanotube forest (CNT-F) supported on a flexible polymer/CNT nanocomposite. Our monolithic electrode generates a stable current density of 10 mA/cm2 at an overpotential (η) of 0.28 V toward the oxygen evolution reaction in 1 M NaOH and reaches approximately 200 mA/cm2 at 1.7 V versus the reversible hydrogen electrode in 6 M KOH. The CNT-F/NiAl electrode also shows an outstanding activity for the hydrogen evolution reaction under alkaline conditions. When CNT-F/NiAl is used both at the anode and at the cathode, our device can sustain the overall water splitting, reaching 10 mA/cm2 at η = 1.96 V. The high electrocatalytic activity of the CNT-F/NiAl hydroxide is due to the huge surface area of the CNT forest, the high electrical conductivity of the nanocomposite substrate, and the interactions between the NiAl catalyst and the CNTs.