Fluorine-doped β-Ni(OH)2–Ti3C2 MXene composite: a bifunctional electrode

Abstract

Developing a multifunctional material with high capacity, vigorous electrocatalytic activity for both the OER and HER, and long-term stability is a significant challenge for electrochemical applications. In this work, a fluorine-doped beta-nickel hydroxide composite with varying Ti₃C₂ concentrations has been synthesized. The F-doped Ni(OH)₂–Ti₃C_{2_}3% (NT-3@NF) electrode exhibits superior electrocatalytic performance compared to other composite electrodes, with overpotentials of 53 mV for the HER and 263 mV for the OER at a current density of 10 mA cm⁻² in a 1 M KOH alkaline electrolyte medium. The fluorine-doped β-Ni(OH)₂ composite with Ti₃C₂ Mxene (β-Ni(OH)₂–Ti₃C₂_3%), referred to as the NT-3 electrode, achieves a practical specific capacity of 242.16 mAh g⁻¹ at a current density of 1 A g⁻¹, which is 83% of the electrode's theoretical specific capacity. A hybrid capacitor with a gel electrolyte, fabricated for both bare and composite electrodes, was configured as AC‖PVA-KOH‖NT-0 and AC‖PVA-KOH‖NT-3, delivering specific energies of 37.21 and 62.13 Wh kg⁻¹, respectively. The long-term cycle stability of the fabricated supercapacitors has been evaluated over approximately 20 000 cycles at a current density of 1 A g⁻¹. The AC‖PVA-KOH‖NT-3 supercapacitor exhibits 71.2% capacitance retention and a coulombic efficiency of 99.62%. A class of 11 V hybrid capacitor prototypes was also fabricated, and their practical viability has been analyzed to ensure high energy density. Thus, the synthesized multifunctional β-Ni(OH)₂ and F-doped β-Ni(OH)₂–Ti₃C₂ composite electrode can be a promising candidate for a highly efficient electrode for energy conversion and storage applications.