CoOx-NCNT-Supported NiFe-Selenide Nanosheets as an Efficient Bifunctional Electrocatalyst for Water Splitting

Efficient and stable electrocatalysts play a fundamental role in advancing the kinetics of water splitting for clean hydrogen production. Transition-metal selenides have been explored as viable candidates for water splitting due to their high abundance and remarkable activities. In this work, we present a novel and versatile strategy to synthesize a high-performance electrocatalyst (NiFeSe@CoOx-NCNTs) that exhibits excellent electrocatalytic activity for both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER). NiFeSe@CoOx-NCNTs have been fabricated by the selenization of NiFe-LDH/CoOx-NCNTs which were synthesized by adopting a hydrothermal approach. The resulting material demonstrates an OER overpotential (η) of only 240 mV at 20 mA/cm2, accompanied by a small Tafel value of 59.2 mV/dec. The catalyst also exhibits outstanding electrocatalytic activity toward HER with an η of 145 mV at 20 mA/cm2. The better HER kinetics on the surface of NiFeSe@CoOx-NCNTs is further supported by a small Tafel slope of ∼169 mV/dec. The small charge transfer resistance (Rct) experienced by NiFeSe@CoOx-NCNTs during both the OER and HER is an indication of the fast movement of active species, which contributes to the enhanced electrocatalytic activity. The high stability of NiFeSe@CoOx-NCNTs for a period of 15 h makes the electrocatalyst an appealing candidate for energy conversion systems.