Multifunctional nitrogen doped carbon nanotube-encapsulated defect-rich cobalt-iron oxide catalyst for efficient water electrolysis and and dye removal from water

The development of robust, high-performance catalytic materials is essential for addressing the interlinked issues of sustainable clean energy conversion and water purification technologies. A simple single-step vacuum annealing method was utilized to enable the controlled conversion of cobalt-iron-Prussian blue analogue (CFPBA) into nitrogen-doped cobalt-iron oxide (NCFO_x) nanoparticles, distinguished by oxygen vacancy-rich surfaces and uniformly encased within an Nitrogen-doped Carbon Nanotube (NCNT) shell structure. The synthesized NCFO_x/NCNT catalyst demonstrates outstanding Oxygen Evolution Reaction (OER) performance, exhibiting an overpotential of only 215 mV at 10 mA cm⁻² and 297 mV at 50 mA cm⁻², coupled with remarkable long-term stability for around 40 h. Moreover, the NCFO_x/NCNT exhibits 100 % removal of Crystal Violet (CrV) dye after 5 min only, surpassing CFPBA/CNT (49 %) and CNTs (19 %) under similar conditions. The NCFO_x/NCNT core–shell nanostructure, which includes N-doping and oxygen vacancy, is considered one of the most remarkable CNTs modified by Co and Fe catalysts. This study offers an original viewpoint on the impacts of defects and proposes a comprehensive approach to develop cost-effective improvements that enhance the efficiency of both OER and dye removal from water.