Tailoring CoNi₂Se₄@Ti₂NbC₂T_<i>x</i> MXene as a Bifunctional Nanocomposite Electrocatalyst for Overall Water Splitting and an Electrode Material for Supercapacitors

In recent advancements, bimetal MXene has emerged as a promising electrocatalyst as well as a catalytic supportive material due to its unique properties, including rich chemistry and potential metal-like conductivity. This study introduces a novel bifunctional electrocatalyst for overall water splitting, involving the synthesis of sea urchin-like CoNi2Se4 onto Ti2NbC2Tx using a simple two-step solvothermal method. The developed CoNi2Se4@Ti2NbC2Tx is subjected to physical and surface topographical investigation using X-ray diffraction, field-emission scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy techniques. The synergistic effect of the prepared bifunctional nanocomposite shows extraordinary kinetic metrics for both HER and OER processes. It shows a low overpotential of 76 mV at 10 mA cm–2 and a small Tafel slope of 78.6 mV dec–1 for the HER and an overpotential of 203 mV at 10 mA cm–2 with a Tafel slope of 102.2 mV dec–1 for the OER. CoNi2Se4@Ti2NbC2Tx exhibits a lower exchange current density with an onset potential that highlights its enhanced performance. This CoNi2Se4@Ti2NbC2Tx electrocatalyst has achieved a current density of 10 mA cm–2 at 1.55 V and maintained excellent electrocatalytic stability for 24 h. It reveals that CoNi2Se4@Ti2NbC2Tx could be used as a cost-effective and efficient catalyst, paving the way for its application in clean hydrogen production through overall water splitting. Owing to its better electrochemical behavior, the prepared CoNi2Se4@Ti2NbC2Tx material is also used as the electrode material for supercapacitor applications, and it exhibits a specific capacitance of about 2.05 F cm–2 at 2 mA cm–2.