Ionic liquid in-situ functionalized carbon nanotube film as self-supported metal-free electrocatalysts for oxygen evolution

The oxygen evolution reaction (OER) is a critical cathode reaction for hydrogen production from water splitting. However, due to the sluggish kinetics of OER, the water-splitting process is impeded. Thus, it is imperative to develop efficient and low-cost electrocatalysts that reduce the overpotential and improve the kinetics of OER. Herein, an in-situ synthesis strategy was applied to prepare the ionic liquid functionalized carbon nanotube (IL-CNT) that served as a metal-free electrocatalyst for OER. This powder material exhibited exceptional electrocatalytic activity for OER, with an overpotential of 335 mV at 10 mA cm−2 and a Tafel slope of 71 mV dec-1. Then, it was found that catalytic activity was influenced by the IL anion. Moreover, this IL-CNT powder could self-assemble to form carbon film during preparation, exhibiting outstanding catalytic activity for OER (a low overpotential of 153 mV at 10 mA cm−2), which was highly beneficial for practical application. Based on the theoretical calculations and experimental results, these in-situ functionalization sites on CNT surface played a significant role in regulating their electron structure. This, in turn, promoted electron transfer and hydroxyl adsorption, resulting in a substantial increase in catalytic activity for the OER.