N-doped carbon nanotubes with high amount of graphitic nitrogen as an excellent electrocatalyst for water splitting in alkaline solution

Nitrogen-doped carbon nanotubes (NCNTs) containing high amounts of graphitic nitrogen (g-N) deposited on nickel foam (NF) are investigated as catalysts for the hydrogen (HER) and oxygen evolution reaction (OER) in alkaline solution. NCNTs with abundant g-N were synthesised on NF at a low temperature (600 °C) via atmospheric pressure chemical vapor deposition over electrodeposited Fe particles. The physicochemical characteristics of NCNTs@NF hybrid electrodes were investigated by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy and compared to those of graphene@NF, ultrathin graphite@NF, and N-doped graphite@NF. The electrochemical activity towards both the HER and OER on all samples was evaluated by linear sweep voltammetry. Experimental results paired with density functional theory (DFT) calculations revealed the contribution of both the metal substrate and the NCNTs to improve the HER performance. DFT results indicate that NCNTs containing high amounts of g-N are a very promising electrocatalyst for water splitting. Furthermore, this study will motivate a direction for reasonable design defects to improve the electrochemical performance of CNTs and consequently meet the targeted requirement of new clean energy devices.