Metal Selenide Anchored Carbon Nanotube for Boosted Oxygen Evolution Reaction

Abstract

The oxygen evolution represents an important reaction in electrochemical water splitting and metal-air batteries. To deal with the increasing energy crisis and demand for sustainable clean energy, production of low-cost, high-efficiency, and robust oxygen evolution reaction (OER) electrocatalysts is urgently needed. Recently, transition metal chalcogenides (TMCs) have been used as active electrocatalysts for OER because of their high electrical conductivity and enhanced electrochemical activity. These chalcogenides based electrocatalysts show unprecedented high efficiency for OER exhibiting very low overpotentials, thereby surpassing state-of-the-art precious metal oxides or hydroxide-based catalysts. Carbon nanostructures have been shown to significantly improve their electrocatalytic performance even further. In the present work, nickel selenide nanorods (NRs) were grown inside carbon nanotubes (NiSe@CNT) through chemical vapor deposition (CVD) wherein, the carbon nanotube formed in-situ wrapping around the growing nickel selenide nanorods. Such intimate intermixing is expected to aid in rapid electron transfer from the catalyst composite and yield significantly higher current density. The encapsulation with a CNT shell can also expectedly increase stability of the selenide phase with respect to corrosion and anion leaching. Electrocatalytic behavior was explored by various electrochemical studies, including linear sweep voltammetry (LSV), chronoamperometric experiments, electrochemical surface area determination, and Tafel slope determination, under highly alkaline condition. It was observed that this NiSe@CNT composites showed enhanced electrocatalytic activity for OER. Our results indicate that the self-grown CNT around nickel selenide increases catalytic activity of this hybrid nanostructure due to an increased number of catalytic sites and electronic conductivity of the nanocomposite. The overpotential at 10 mA cm-2 for the as-synthesized NiSe@CNT catalyst is 270 mV which is much better than precious metal based electrocatalysts for OER, such as RuO2 and IrO2. In addition, the current-voltage plots were superimposable before and after 40 h of chronoamperometry test, confirming that the as-synthesized catalyst gives stable electrocatalytic OER activity in 1 M KOH medium for an extended time period. The as-synthesized catalyst was characterized by XRD, Raman spectroscopy, XPS and TEM for morphology, elemental and chemical compositions.Keywords: oxygen evolution reaction, carbon nanotubes, In-situ wrapping Figure 1